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Updated iOS tutorials
This commit is contained in:
Olivier Crête
parent
1912801c9c
commit
1c35f99e7a
11
TODO.md
11
TODO.md
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@ -4,11 +4,6 @@ This is just a simple TODO list to follow progress of the port from
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gstreamer.com content to hotdoc
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Pages to review:
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- sdk-ios-tutorials.md
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- sdk-ios-tutorial-link-against-gstreamer.md
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- sdk-ios-tutorial-a-running-pipeline.md
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- sdk-ios-tutorial-video.md
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- sdk-ios-tutorial-a-basic-media-player.md
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- [installing]
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- sdk-installing-for-ios-development.md
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- sdk-installing-on-linux.md
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@ -24,6 +19,7 @@ Screenshots:
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- Create new ones with the official GStreamer logo and not saying "0.10.36". Affected:
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- Android tutorial 1
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- Android tutorial 2
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- iOS tutorial 1
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- Fix filenames of all attachments to make sense
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Code:
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@ -57,6 +53,11 @@ Reviewed pages:
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- sdk-android-tutorial-video.md
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- sdk-android-tutorial-a-complete-media-player.md
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- sdk-android-tutorial-media-player.md
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- sdk-ios-tutorials.md
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- sdk-ios-tutorial-link-against-gstreamer.md
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- sdk-ios-tutorial-a-running-pipeline.md
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- sdk-ios-tutorial-video.md
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- sdk-ios-tutorial-a-basic-media-player.md
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- sdk-playback-tutorials.md
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- sdk-playback-tutorial-playbin-usage.md
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- sdk-playback-tutorial-subtitle-management.md
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@ -1,46 +1,47 @@
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# iOS tutorial 4: A basic media player
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# Goal
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## Goal
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Enough testing with synthetic images and audio tones\! This tutorial
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![screenshot]
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Enough testing with synthetic images and audio tones! This tutorial
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finally plays actual media, streamed directly from the Internet, in your
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iOS device. It shows:
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- How to keep the User Interface regularly updated with the current
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playback position and duration
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- How to implement a [Time
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- How to implement a [Time
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Slider](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UISlider_Class/Reference/Reference.html)
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- How to report the media size to adapt the display surface
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It also uses the knowledge gathered in the [Basic
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tutorials](Basic%2Btutorials.html) regarding:
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It also uses the knowledge gathered in the [](sdk-basic-tutorials.md) regarding:
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- How to use `playbin` to play any kind of media
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- How to use `playbin` to play any kind of media
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- How to handle network resilience problems
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# Introduction
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## Introduction
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From the previous tutorials, we already have almost all necessary pieces
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to build a media player. The most complex part is assembling a pipeline
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which retrieves, decodes and displays the media, but we already know
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that the `playbin` element can take care of all that for us. We only
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need to replace the manual pipeline we used in [iOS tutorial 3:
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Video](iOS%2Btutorial%2B3%253A%2BVideo.html) with a
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single-element `playbin` pipeline and we are good to go\!
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From the previous tutorials, we already have almost all necessary
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pieces to build a media player. The most complex part is assembling a
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pipeline which retrieves, decodes and displays the media, but we
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already know that the `playbin` element can take care of all that for
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us. We only need to replace the manual pipeline we used in
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[](sdk-ios-tutorial-video.md) with a single-element `playbin` pipeline
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and we are good to go!
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However, we can do better than. We will add a [Time
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However, we can do better than. We will add a [Time
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Slider](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UISlider_Class/Reference/Reference.html),
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with a moving thumb that will advance as our current position in the
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media advances. We will also allow the user to drag the thumb, to jump
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(or *seek*) to a different position.
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(or *seek*) to a different position.
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And finally, we will make the video surface adapt to the media size, so
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the video sink is not forced to draw black borders around the clip.
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This also allows the iOS layout to adapt more nicely to the actual
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This also allows the iOS layout to adapt more nicely to the actual
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media content. You can still force the video surface to have a specific
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size if you really want to.
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# The User Interface
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## The User Interface
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The User Interface from the previous tutorial is expanded again. A
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`UISlider` has been added to the toolbar, to keep track of the current
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@ -83,15 +84,15 @@ duration.
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```
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Note how we register callbacks for some of the Actions the
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[UISlider](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UISlider_Class/Reference/Reference.html) generates.
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Also note that the class has been renamed from `ViewController` to
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[UISlider](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UISlider_Class/Reference/Reference.html) generates.
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Also note that the class has been renamed from `ViewController` to
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`VideoViewController`, since the next tutorial adds another
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`ViewController` and we will need to differentiate.
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# The Video View Controller
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## The Video View Controller
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The `ViewController `class manages the UI, instantiates
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the `GStreamerBackend` and also performs some UI-related tasks on its
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The `ViewController `class manages the UI, instantiates
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the `GStreamerBackend` and also performs some UI-related tasks on its
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behalf:
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Due to the extension of this code,
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@ -300,14 +301,14 @@ this view is collapsed by default. Click here to expand…
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Supporting arbitrary media URIs
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The `GStreamerBackend` provides the `setUri()` method so we can
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indicate the URI of the media to play. Since `playbin` will be taking
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The `GStreamerBackend` provides the `setUri()` method so we can
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indicate the URI of the media to play. Since `playbin` will be taking
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care of retrieving the media, we can use local or remote URIs
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indistinctly (`file://` or `http://`, for example). From the UI code,
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indistinctly (`file://` or `http://`, for example). From the UI code,
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though, we want to keep track of whether the file is local or remote,
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because we will not offer the same functionalities. We keep track of
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this in the `is_local_media` variable, which is set when the URI is set,
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in the `gstreamerInitialized` method:
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this in the `is_local_media` variable, which is set when the URI is set,
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in the `gstreamerInitialized` method:
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```
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-(void) gstreamerInitialized
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@ -327,7 +328,7 @@ Reporting media size
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Every time the size of the media changes (which could happen mid-stream,
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for some kind of streams), or when it is first detected,
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`GStreamerBackend` calls our `mediaSizeChanged()` callback:
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`GStreamerBackend` calls our `mediaSizeChanged()` callback:
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```
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-(void) mediaSizeChanged:(NSInteger)width height:(NSInteger)height
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@ -343,18 +344,16 @@ for some kind of streams), or when it is first detected,
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```
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Here we simply store the new size and ask the layout to be recalculated.
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As we have already seen in [iOS tutorial 2: A running
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pipeline](iOS%2Btutorial%2B2%253A%2BA%2Brunning%2Bpipeline.html),
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As we have already seen in [](sdk-ios-tutorial-a-running-pipeline.md),
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methods which change the UI must be called from the main thread, and we
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are now in a callback from some GStreamer internal thread. Hence, the
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usage
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of `dispatch_async()`[.](http://developer.android.com/reference/android/app/Activity.html#runOnUiThread\(java.lang.Runnable\))
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of `dispatch_async()`[.](http://developer.android.com/reference/android/app/Activity.html#runOnUiThread\(java.lang.Runnable\))
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### Refreshing the Time Slider
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[Basic tutorial 5: GUI toolkit
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integration](Basic%2Btutorial%2B5%253A%2BGUI%2Btoolkit%2Bintegration.html) has
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already shown how to implement a Seek Bar (or [Time
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[](sdk-basic-tutorial-toolkit-integration.md) has
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already shown how to implement a Seek Bar (or [Time
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Slider](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UISlider_Class/Reference/Reference.html)
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in this tutorial) using the GTK+ toolkit. The implementation on iOS is
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very similar.
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@ -363,8 +362,8 @@ The Seek Bar accomplishes to functions: First, it moves on its own to
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reflect the current playback position in the media. Second, it can be
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dragged by the user to seek to a different position.
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To realize the first function, `GStreamerBackend` will periodically
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call our `setCurrentPosition` method so we can update the position of
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To realize the first function, `GStreamerBackend` will periodically
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call our `setCurrentPosition` method so we can update the position of
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the thumb in the Seek Bar. Again we do so from the UI thread, using
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`dispatch_async()`.
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@ -383,15 +382,15 @@ the thumb in the Seek Bar. Again we do so from the UI thread, using
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```
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Also note that if the user is currently dragging the slider (the
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`dragging_slider` variable is explained below) we ignore
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`setCurrentPosition` calls from `GStreamerBackend`, as they would
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`dragging_slider` variable is explained below) we ignore
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`setCurrentPosition` calls from `GStreamerBackend`, as they would
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interfere with the user’s actions.
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To the left of the Seek Bar (refer to the screenshot at the top of this
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page), there is
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a [TextField](https://developer.apple.com/library/ios/#documentation/UIKit/Reference/UITextField_Class/Reference/UITextField.html) widget
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a [TextField](https://developer.apple.com/library/ios/#documentation/UIKit/Reference/UITextField_Class/Reference/UITextField.html) widget
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which we will use to display the current position and duration in
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"`HH:mm:ss / HH:mm:ss"` textual format. The `updateTimeWidget` method
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"`HH:mm:ss / HH:mm:ss"` textual format. The `updateTimeWidget` method
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takes care of it, and must be called every time the Seek Bar is
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updated:
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@ -429,7 +428,7 @@ updated:
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Seeking with the Seek Bar
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To perform the second function of the Seek Bar (allowing the user to
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To perform the second function of the Seek Bar (allowing the user to
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seek by dragging the thumb), we register some callbacks through IBAction
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outlets. Refer to the storyboard in this tutorial’s project to see which
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outlets are connected. We will be notified when the user starts dragging
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@ -444,11 +443,11 @@ the Slider.
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}
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```
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`sliderTouchDown` is called when the user starts dragging. Here we pause
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`sliderTouchDown` is called when the user starts dragging. Here we pause
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the pipeline because if the user is searching for a particular scene, we
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do not want it to keep moving. We also mark that a drag operation is in
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progress in the
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`dragging_slider` variable.
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`dragging_slider` variable.
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```
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/* Called when the time slider position has changed, either because the user dragged it or
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@ -462,10 +461,10 @@ progress in the
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}
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```
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`sliderValueChanged` is called every time the Slider’s thumb moves, be
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`sliderValueChanged` is called every time the Slider’s thumb moves, be
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it because the user dragged it, or because we changed its value form the
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program. We discard the latter case using the
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`dragging_slider` variable.
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`dragging_slider` variable.
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As the comment says, if this is a local media, we allow scrub seeking,
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this is, we jump to the indicated position as soon as the thumb moves.
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@ -486,24 +485,21 @@ widget.
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}
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```
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Finally, `sliderTouchUp` is called when the thumb is released. We
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Finally, `sliderTouchUp` is called when the thumb is released. We
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perform the seek operation if the file was non-local, restore the
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pipeline to the desired playing state and end the dragging operation by
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setting `dragging_slider` to NO.
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This concludes the User interface part of this tutorial. Let’s review
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now the `GStreamerBackend` class that allows this to work.
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now the `GStreamerBackend` class that allows this to work.
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# The GStreamer Backend
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## The GStreamer Backend
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The `GStreamerBackend` class performs all GStreamer-related tasks and
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The `GStreamerBackend` class performs all GStreamer-related tasks and
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offers a simplified interface to the application, which does not need to
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deal with all the GStreamer details. When it needs to perform any UI
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action, it does so through a delegate, which is expected to adhere to
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the `GStreamerBackendDelegate` protocol.
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Due to the extension of this code,
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this view is collapsed by default. Click here to expand…
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the `GStreamerBackendDelegate` protocol.
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**GStreamerBackend.m**
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@ -511,7 +507,6 @@ this view is collapsed by default. Click here to expand…
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#import "GStreamerBackend.h"
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#include <gst/gst.h>
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#include <gst/interfaces/xoverlay.h>
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#include <gst/video/video.h>
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GST_DEBUG_CATEGORY_STATIC (debug_category);
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@ -530,7 +525,7 @@ GST_DEBUG_CATEGORY_STATIC (debug_category);
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@implementation GStreamerBackend {
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id ui_delegate; /* Class that we use to interact with the user interface */
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GstElement *pipeline; /* The running pipeline */
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GstElement *video_sink; /* The video sink element which receives XOverlay commands */
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GstElement *video_sink; /* The video sink element which receives VideoOverlay commands */
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GMainContext *context; /* GLib context used to run the main loop */
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GMainLoop *main_loop; /* GLib main loop */
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gboolean initialized; /* To avoid informing the UI multiple times about the initialization */
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@ -630,7 +625,6 @@ GST_DEBUG_CATEGORY_STATIC (debug_category);
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/* If we have pipeline and it is running, query the current position and clip duration and inform
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* the application */
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static gboolean refresh_ui (GStreamerBackend *self) {
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GstFormat fmt = GST_FORMAT_TIME;
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gint64 position;
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/* We do not want to update anything unless we have a working pipeline in the PAUSED or PLAYING state */
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@ -639,10 +633,10 @@ static gboolean refresh_ui (GStreamerBackend *self) {
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/* If we didn't know it yet, query the stream duration */
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if (!GST_CLOCK_TIME_IS_VALID (self->duration)) {
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gst_element_query_duration (self->pipeline, &fmt, &self->duration);
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gst_element_query_duration (self->pipeline, GST_FORMAT_TIME, &self->duration);
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}
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if (gst_element_query_position (self->pipeline, &fmt, &position)) {
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if (gst_element_query_position (self->pipeline, GST_FORMAT_TIME, &position)) {
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/* The UI expects these values in milliseconds, and GStreamer provides nanoseconds */
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[self setCurrentUIPosition:position / GST_MSECOND duration:self->duration / GST_MSECOND];
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}
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@ -756,9 +750,7 @@ static void check_media_size (GStreamerBackend *self) {
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GstElement *video_sink;
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GstPad *video_sink_pad;
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GstCaps *caps;
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GstVideoFormat fmt;
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int width;
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int height;
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GstVideoInfo info;
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/* Retrieve the Caps at the entrance of the video sink */
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g_object_get (self->pipeline, "video-sink", &video_sink, NULL);
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@ -767,18 +759,15 @@ static void check_media_size (GStreamerBackend *self) {
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if (!video_sink) return;
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video_sink_pad = gst_element_get_static_pad (video_sink, "sink");
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caps = gst_pad_get_negotiated_caps (video_sink_pad);
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caps = gst_pad_get_current_caps (video_sink_pad);
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if (gst_video_format_parse_caps(caps, &fmt, &width, &height)) {
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int par_n, par_d;
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if (gst_video_parse_caps_pixel_aspect_ratio (caps, &par_n, &par_d)) {
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width = width * par_n / par_d;
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}
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GST_DEBUG ("Media size is %dx%d, notifying application", width, height);
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if (gst_video_info_from_caps(&info, caps)) {
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info.width = info.width * info.par_n / info.par_d
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GST_DEBUG ("Media size is %dx%d, notifying application", info.width, info.height);
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if (self->ui_delegate && [self->ui_delegate respondsToSelector:@selector(mediaSizeChanged:height:)])
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if (self->ui_delegate && [self->ui_delegate respondsToSelector:@selector(mediaSizeChanged:info.height:)])
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{
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[self->ui_delegate mediaSizeChanged:width height:height];
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[self->ui_delegate mediaSizeChanged:info.width height:info.height];
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}
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}
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@ -851,12 +840,12 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
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/* Set the pipeline to READY, so it can already accept a window handle */
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gst_element_set_state(pipeline, GST_STATE_READY);
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video_sink = gst_bin_get_by_interface(GST_BIN(pipeline), GST_TYPE_X_OVERLAY);
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video_sink = gst_bin_get_by_interface(GST_BIN(pipeline), GST_TYPE_VIDEO_OVERLAY);
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if (!video_sink) {
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GST_ERROR ("Could not retrieve video sink");
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return;
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}
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gst_x_overlay_set_window_handle(GST_X_OVERLAY(video_sink), (guintptr) (id) ui_video_view);
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gst_video_overlay_set_window_handle(GST_VIDEO_OVERLAY(video_sink), (guintptr) (id) ui_video_view);
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/* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
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bus = gst_element_get_bus (pipeline);
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@ -905,7 +894,7 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
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Supporting arbitrary media URIs
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The UI code will call `setUri` whenever it wants to change the playing
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The UI code will call `setUri` whenever it wants to change the playing
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URI (in this tutorial the URI never changes, but it does in the next
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one):
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@ -918,11 +907,11 @@ one):
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}
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```
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||||
We first need to obtain a plain `char *` from within the `NSString *` we
|
||||
get, using the `UTF8String` method.
|
||||
We first need to obtain a plain `char *` from within the `NSString *` we
|
||||
get, using the `UTF8String` method.
|
||||
|
||||
`playbin`’s URI is exposed as a common GObject property, so we simply
|
||||
set it with `g_object_set()`.
|
||||
set it with `g_object_set()`.
|
||||
|
||||
### Reporting media size
|
||||
|
||||
|
|
@ -930,7 +919,7 @@ Some codecs allow the media size (width and height of the video) to
|
|||
change during playback. For simplicity, this tutorial assumes that they
|
||||
do not. Therefore, in the READY to PAUSED state change, once the Caps of
|
||||
the decoded media are known, we inspect them
|
||||
in `check_media_size()`:
|
||||
in `check_media_size()`:
|
||||
|
||||
```
|
||||
/* Retrieve the video sink's Caps and tell the application about the media size */
|
||||
|
|
@ -938,9 +927,7 @@ static void check_media_size (GStreamerBackend *self) {
|
|||
GstElement *video_sink;
|
||||
GstPad *video_sink_pad;
|
||||
GstCaps *caps;
|
||||
GstVideoFormat fmt;
|
||||
int width;
|
||||
int height;
|
||||
GstVideoInfo info;
|
||||
|
||||
/* Retrieve the Caps at the entrance of the video sink */
|
||||
g_object_get (self->pipeline, "video-sink", &video_sink, NULL);
|
||||
|
|
@ -949,18 +936,15 @@ static void check_media_size (GStreamerBackend *self) {
|
|||
if (!video_sink) return;
|
||||
|
||||
video_sink_pad = gst_element_get_static_pad (video_sink, "sink");
|
||||
caps = gst_pad_get_negotiated_caps (video_sink_pad);
|
||||
caps = gst_pad_get_current_caps (video_sink_pad);
|
||||
|
||||
if (gst_video_format_parse_caps(caps, &fmt, &width, &height)) {
|
||||
int par_n, par_d;
|
||||
if (gst_video_parse_caps_pixel_aspect_ratio (caps, &par_n, &par_d)) {
|
||||
width = width * par_n / par_d;
|
||||
}
|
||||
GST_DEBUG ("Media size is %dx%d, notifying application", width, height);
|
||||
if (gst_video_info_from_caps(&info, caps)) {
|
||||
info.width = info.width * info.par_n / info.par_d;
|
||||
GST_DEBUG ("Media size is %dx%d, notifying application", info.width, info.height);
|
||||
|
||||
if (self->ui_delegate && [self->ui_delegate respondsToSelector:@selector(mediaSizeChanged:height:)])
|
||||
if (self->ui_delegate && [self->ui_delegate respondsToSelector:@selector(mediaSizeChanged:info.height:)])
|
||||
{
|
||||
[self->ui_delegate mediaSizeChanged:width height:height];
|
||||
[self->ui_delegate mediaSizeChanged:info.width height:info.height];
|
||||
}
|
||||
}
|
||||
|
||||
|
|
@ -971,19 +955,19 @@ static void check_media_size (GStreamerBackend *self) {
|
|||
```
|
||||
|
||||
We first retrieve the video sink element from the pipeline, using
|
||||
the `video-sink` property of `playbin`, and then its sink Pad. The
|
||||
the `video-sink` property of `playbin`, and then its sink Pad. The
|
||||
negotiated Caps of this Pad, which we recover using
|
||||
`gst_pad_get_negotiated_caps()`, are the Caps of the decoded media.
|
||||
`gst_pad_get_current_caps()`, are the Caps of the decoded media.
|
||||
|
||||
The helper functions `gst_video_format_parse_caps()` and
|
||||
`gst_video_parse_caps_pixel_aspect_ratio()` turn the Caps into
|
||||
The helper functions `gst_video_format_parse_caps()` and
|
||||
`gst_video_parse_caps_pixel_aspect_ratio()` turn the Caps into
|
||||
manageable integers, which we pass to the application through
|
||||
its `mediaSizeChanged` callback.
|
||||
its `mediaSizeChanged` callback.
|
||||
|
||||
### Refreshing the Seek Bar
|
||||
|
||||
To keep the UI updated, a GLib timer is installed in
|
||||
the `app_function` that fires 4 times per second (or every 250ms),
|
||||
the `app_function` that fires 4 times per second (or every 250ms),
|
||||
right before entering the main loop:
|
||||
|
||||
```
|
||||
|
|
@ -1001,7 +985,6 @@ method:
|
|||
/* If we have pipeline and it is running, query the current position and clip duration and inform
|
||||
* the application */
|
||||
static gboolean refresh_ui (GStreamerBackend *self) {
|
||||
GstFormat fmt = GST_FORMAT_TIME;
|
||||
gint64 position;
|
||||
|
||||
/* We do not want to update anything unless we have a working pipeline in the PAUSED or PLAYING state */
|
||||
|
|
@ -1010,10 +993,10 @@ static gboolean refresh_ui (GStreamerBackend *self) {
|
|||
|
||||
/* If we didn't know it yet, query the stream duration */
|
||||
if (!GST_CLOCK_TIME_IS_VALID (self->duration)) {
|
||||
gst_element_query_duration (self->pipeline, &fmt, &self->duration);
|
||||
gst_element_query_duration (self->pipeline, GST_FORMAT_TIME, &self->duration);
|
||||
}
|
||||
|
||||
if (gst_element_query_position (self->pipeline, &fmt, &position)) {
|
||||
if (gst_element_query_position (self->pipeline, GST_FORMAT_TIME, &position)) {
|
||||
/* The UI expects these values in milliseconds, and GStreamer provides nanoseconds */
|
||||
[self setCurrentUIPosition:position / GST_MSECOND duration:self->duration / GST_MSECOND];
|
||||
}
|
||||
|
|
@ -1021,21 +1004,20 @@ static gboolean refresh_ui (GStreamerBackend *self) {
|
|||
}
|
||||
```
|
||||
|
||||
If it is unknown, the clip duration is retrieved, as explained in [Basic
|
||||
tutorial 4: Time
|
||||
management](Basic%2Btutorial%2B4%253A%2BTime%2Bmanagement.html). The
|
||||
current position is retrieved next, and the UI is informed of both
|
||||
through its `setCurrentUIPosition` callback.
|
||||
If it is unknown, the clip duration is retrieved, as explained in
|
||||
[](sdk-basic-tutorial-time-management.md). The current position is
|
||||
retrieved next, and the UI is informed of both through its
|
||||
`setCurrentUIPosition` callback.
|
||||
|
||||
Bear in mind that all time-related measures returned by GStreamer are in
|
||||
nanoseconds, whereas, for simplicity, we decided to make the UI code
|
||||
work in milliseconds.
|
||||
work in milliseconds.
|
||||
|
||||
### Seeking with the Seek Bar
|
||||
|
||||
The UI code already takes care of most of the complexity of seeking by
|
||||
dragging the thumb of the Seek Bar. From the `GStreamerBackend`, we just
|
||||
need to honor the calls to `setPosition` and instruct the pipeline to
|
||||
need to honor the calls to `setPosition` and instruct the pipeline to
|
||||
jump to the indicated position.
|
||||
|
||||
There are, though, a couple of caveats. Firstly, seeks are only possible
|
||||
|
|
@ -1047,7 +1029,7 @@ see how to overcome these problems.
|
|||
|
||||
#### Delayed seeks
|
||||
|
||||
In `setPosition`:
|
||||
In `setPosition`:
|
||||
|
||||
```
|
||||
-(void) setPosition:(NSInteger)milliseconds
|
||||
|
|
@ -1064,8 +1046,8 @@ In `setPosition`:
|
|||
|
||||
If we are already in the correct state for seeking, execute it right
|
||||
away; otherwise, store the desired position in
|
||||
the `desired_position` variable. Then, in
|
||||
the `state_changed_cb()` callback:
|
||||
the `desired_position` variable. Then, in
|
||||
the `state_changed_cb()` callback:
|
||||
|
||||
```
|
||||
if (old_state == GST_STATE_READY && new_state == GST_STATE_PAUSED)
|
||||
|
|
@ -1080,7 +1062,7 @@ the `state_changed_cb()` callback:
|
|||
|
||||
Once the pipeline moves from the READY to the PAUSED state, we check if
|
||||
there is a pending seek operation and execute it.
|
||||
The `desired_position` variable is reset inside `execute_seek()`.
|
||||
The `desired_position` variable is reset inside `execute_seek()`.
|
||||
|
||||
#### Seek throttling
|
||||
|
||||
|
|
@ -1097,11 +1079,11 @@ second one, it is up to it to finish the first one, start the second one
|
|||
or abort both, which is a bad thing. A simple method to avoid this issue
|
||||
is *throttling*, which means that we will only allow one seek every half
|
||||
a second (for example): after performing a seek, only the last seek
|
||||
request received during the next 500ms is stored, and will be honored
|
||||
request received during the next 500ms is stored, and will be honored
|
||||
once this period elapses.
|
||||
|
||||
To achieve this, all seek requests are routed through
|
||||
the `execute_seek()` method:
|
||||
To achieve this, all seek requests are routed through
|
||||
the `execute_seek()` method:
|
||||
|
||||
```
|
||||
/* Perform seek, if we are not too close to the previous seek. Otherwise, schedule the seek for
|
||||
|
|
@ -1141,34 +1123,28 @@ static void execute_seek (gint64 position, GStreamerBackend *self) {
|
|||
```
|
||||
|
||||
The time at which the last seek was performed is stored in
|
||||
the `last_seek_time` variable. This is wall clock time, not to be
|
||||
the `last_seek_time` variable. This is wall clock time, not to be
|
||||
confused with the stream time carried in the media time stamps, and is
|
||||
obtained with `gst_util_get_timestamp()`.
|
||||
|
||||
If enough time has passed since the last seek operation, the new one is
|
||||
directly executed and `last_seek_time` is updated. Otherwise, the new
|
||||
directly executed and `last_seek_time` is updated. Otherwise, the new
|
||||
seek is scheduled for later. If there is no previously scheduled seek, a
|
||||
one-shot timer is setup to trigger 500ms after the last seek operation.
|
||||
If another seek was already scheduled, its desired position is simply
|
||||
updated with the new one.
|
||||
|
||||
The one-shot timer calls `delayed_seek_cb()`, which simply
|
||||
calls `execute_seek()` again.
|
||||
The one-shot timer calls `delayed_seek_cb()`, which simply
|
||||
calls `execute_seek()` again.
|
||||
|
||||
<table>
|
||||
<tbody>
|
||||
<tr class="odd">
|
||||
<td><img src="images/icons/emoticons/information.png" width="16" height="16" /></td>
|
||||
<td><p><span>Ideally, </span><code>execute_seek()</code><span> will now find that enough time has indeed passed since the last seek and the scheduled one will proceed. It might happen, though, that after 500ms of the previous seek, and before the timer wakes up, yet another seek comes through and is executed. </span><code>delayed_seek_cb()</code><span> needs to check for this condition to avoid performing two very close seeks, and therefore calls </span><code>execute_seek()</code><span> instead of performing the seek itself.</span></p>
|
||||
<p>This is not a complete solution: the scheduled seek will still be executed, even though a more-recent seek has already been executed that should have cancelled it. However, it is a good tradeoff between functionality and simplicity.</p></td>
|
||||
</tr>
|
||||
</tbody>
|
||||
</table>
|
||||
> ![information]
|
||||
> Ideally, `execute_seek()` will now find that enough time has indeed passed since the last seek and the scheduled one will proceed. It might happen, though, that after 500ms of the previous seek, and before the timer wakes up, yet another seek comes through and is executed. `delayed_seek_cb()` needs to check for this condition to avoid performing two very close seeks, and therefore calls `execute_seek()` instead of performing the seek itself.
|
||||
>
|
||||
>This is not a complete solution: the scheduled seek will still be executed, even though a more-recent seek has already been executed that should have cancelled it. However, it is a good tradeoff between functionality and simplicity.
|
||||
|
||||
Network resilience
|
||||
### Network resilience
|
||||
|
||||
[Basic tutorial 12:
|
||||
Streaming](Basic%2Btutorial%2B12%253A%2BStreaming.html) has already
|
||||
[](sdk-basic-tutorial-streaming.md) has already
|
||||
shown how to adapt to the variable nature of the network bandwidth by
|
||||
using buffering. The same procedure is used here, by listening to the
|
||||
buffering
|
||||
|
|
@ -1182,7 +1158,7 @@ And pausing the pipeline until buffering is complete (unless this is a
|
|||
live
|
||||
source):
|
||||
|
||||
|
||||
|
||||
|
||||
```
|
||||
/* Called when buffering messages are received. We inform the UI about the current buffering level and
|
||||
|
|
@ -1207,14 +1183,14 @@ static void buffering_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *self)
|
|||
}
|
||||
```
|
||||
|
||||
`target_state` is the state in which we have been instructed to set the
|
||||
`target_state` is the state in which we have been instructed to set the
|
||||
pipeline, which might be different to the current state, because
|
||||
buffering forces us to go to PAUSED. Once buffering is complete we set
|
||||
the pipeline to the `target_state`.
|
||||
the pipeline to the `target_state`.
|
||||
|
||||
### Conclusion
|
||||
## Conclusion
|
||||
|
||||
This tutorial has shown how to embed a `playbin` pipeline into an iOS
|
||||
This tutorial has shown how to embed a `playbin` pipeline into an iOS
|
||||
application. This, effectively, turns such application into a basic
|
||||
media player, capable of streaming and decoding all the formats
|
||||
GStreamer understands. More particularly, it has shown:
|
||||
|
|
@ -1230,8 +1206,5 @@ GStreamer understands. More particularly, it has shown:
|
|||
The next tutorial adds the missing bits to turn the application built
|
||||
here into an acceptable iOS media player.
|
||||
|
||||
## Attachments:
|
||||
|
||||
|
||||
[ios-tutorial4-screenshot.png](attachments/3571758/3539044.png)
|
||||
(image/png)
|
||||
[information]: images/icons/emoticons/information.png
|
||||
[screenshot]: images/sdk-ios-tutorial-a-basic-media-player-screenshot.png
|
||||
|
|
@ -1,20 +1,22 @@
|
|||
# iOS tutorial 5: A Complete media player
|
||||
|
||||
# Goal
|
||||
## Goal
|
||||
|
||||
![screenshot0]
|
||||
![screenshot1]
|
||||
|
||||
This tutorial wants to be the “demo application” that showcases what can
|
||||
be done with GStreamer on the iOS platform.
|
||||
|
||||
It is intended to be built and run, rather than analyzed for its
|
||||
pedagogical value, since it adds very little GStreamer knowledge over
|
||||
what has already been shown in [iOS tutorial 4: A basic media
|
||||
player](iOS%2Btutorial%2B4%253A%2BA%2Bbasic%2Bmedia%2Bplayer.html).
|
||||
what has already been shown in [](sdk-ios-tutorial-a-basic-media-player.md).
|
||||
|
||||
It demonstrates the main functionality that a conventional media player
|
||||
has, but it is not a complete application yet, therefore it has not been
|
||||
uploaded to the AppStore.
|
||||
|
||||
# Introduction
|
||||
## Introduction
|
||||
|
||||
The previous tutorial already implemented a basic media player. This one
|
||||
simply adds a few finishing touches. In particular, it adds the
|
||||
|
|
@ -25,12 +27,11 @@ These are not features directly related to GStreamer, and are therefore
|
|||
outside the scope of these tutorials. Only a few implementation pointers
|
||||
are given here.
|
||||
|
||||
# Selecting the media to play
|
||||
## Selecting the media to play
|
||||
|
||||
A new `UIView` has been added, derived from `UITableViewController`
|
||||
which shows a list of clips. When one is selected, the
|
||||
`VideoViewController` from [Tutorial
|
||||
4](iOS%2Btutorial%2B4%253A%2BA%2Bbasic%2Bmedia%2Bplayer.html) appears
|
||||
`VideoViewController` from [](sdk-ios-tutorial-a-basic-media-player.md) appears
|
||||
and its URI property is set to the URI of the selected clip.
|
||||
|
||||
The list of clips is populated from three sources: Media from the
|
||||
|
|
@ -39,17 +40,17 @@ device’s Photo library, Media from the application’s Documents folder
|
|||
Internet addresses, selected to showcase different container and codec
|
||||
formats, and a couple of bogus ones, to illustrate error reporting.
|
||||
|
||||
# Preventing the screen from turning off
|
||||
## Preventing the screen from turning off
|
||||
|
||||
While watching a movie, there is typically no user activity. After a
|
||||
short period of such inactivity, iOS will dim the screen, and then turn
|
||||
it off completely. To prevent this, the `idleTimerDisabled` property of
|
||||
the `UIApplication` class is used. The application sets it to YES
|
||||
it off completely. To prevent this, the `idleTimerDisabled` property of
|
||||
the `UIApplication` class is used. The application sets it to YES
|
||||
(screen locking disabled) when the Play button is pressed, so the screen
|
||||
is never turned off, and sets it back to NO when the Pause button is
|
||||
pressed.
|
||||
|
||||
# Conclusion
|
||||
## Conclusion
|
||||
|
||||
This finishes the series of iOS tutorials. Each one of the preceding
|
||||
tutorials has evolved on top of the previous one, showing how to
|
||||
|
|
@ -57,16 +58,7 @@ implement a particular set of features, and concluding in this Tutorial
|
|||
5. The goal of Tutorial 5 is to build a complete media player which can
|
||||
already be used to showcase the integration of GStreamer and iOS.
|
||||
|
||||
It has been a pleasure having you here, and see you soon\!
|
||||
It has been a pleasure having you here, and see you soon!
|
||||
|
||||
## Attachments:
|
||||
|
||||
|
||||
[ios-tutorial5-screenshot0.png](attachments/3571769/3539071.png)
|
||||
(image/png)
|
||||
|
||||
[ios-tutorial5-screenshot1.png](attachments/3571769/3539046.png)
|
||||
(image/png)
|
||||
|
||||
[ios-tutorial5-screenshot0.png](attachments/3571769/3539045.png)
|
||||
(image/png)
|
||||
[screenshot0]: images/sdk-ios-tutorial-a-complete-media-player-screenshot-0.png
|
||||
[screenshot1]: images/sdk-ios-tutorial-a-complete-media-player-screenshot-1.png
|
||||
|
|
|
|||
|
|
@ -1,9 +1,11 @@
|
|||
# iOS tutorial 2: A running pipeline
|
||||
|
||||
# Goal
|
||||
## Goal
|
||||
|
||||
As seen in the [Basic](Basic%2Btutorials.html) and
|
||||
[Playback](Playback%2Btutorials.html) tutorials, GStreamer integrates
|
||||
![screenshot]
|
||||
|
||||
As seen in the [Basic](sdk-basic-tutorials.md) and
|
||||
[Playback](sdk-playback-tutorials.md) tutorials, GStreamer integrates
|
||||
nicely with GLib’s main loops, so pipeline operation and user interface
|
||||
can be monitored simultaneously in a very simple way. However, platforms
|
||||
like iOS or Android do not use GLib and therefore extra care must be
|
||||
|
|
@ -17,18 +19,18 @@ This tutorial shows:
|
|||
- How to communicate between the Objective-C UI code and the C
|
||||
GStreamer code
|
||||
|
||||
# Introduction
|
||||
## Introduction
|
||||
|
||||
When using a Graphical User Interface (UI), if the application waits for
|
||||
GStreamer calls to complete the user experience will suffer. The usual
|
||||
approach, with the [GTK+ toolkit](http://www.gtk.org/) for example, is
|
||||
to relinquish control to a GLib `GMainLoop` and let it control the
|
||||
approach, with the [GTK+ toolkit](http://www.gtk.org/) for example, is
|
||||
to relinquish control to a GLib `GMainLoop` and let it control the
|
||||
events coming from the UI or GStreamer.
|
||||
|
||||
Other graphical toolkits that are not based on GLib, like the [Cocoa
|
||||
Touch](https://developer.apple.com/technologies/ios/cocoa-touch.html)
|
||||
Touch](https://developer.apple.com/library/ios/documentation/General/Conceptual/DevPedia-CocoaCore/Cocoa.html)
|
||||
framework used on iOS devices, cannot use this option, though. The
|
||||
solution used in this tutorial uses a GLib `GMainLoop` for its
|
||||
solution used in this tutorial uses a GLib `GMainLoop` for its
|
||||
simplicity, but moves it to a separate thread (a [Dispatch
|
||||
Queue](http://developer.apple.com/library/ios/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html)
|
||||
different than the main one) so it does not block the user interface
|
||||
|
|
@ -37,12 +39,12 @@ operation.
|
|||
Additionally, this tutorial shows a few places where caution has to be
|
||||
taken when calling from Objective-C to C and vice versa.
|
||||
|
||||
The code below builds a pipeline with an `audiotestsrc` and
|
||||
an `autoaudiosink` (it plays an audible tone). Two buttons in the UI
|
||||
The code below builds a pipeline with an `audiotestsrc` and
|
||||
an `autoaudiosink` (it plays an audible tone). Two buttons in the UI
|
||||
allow setting the pipeline to PLAYING or PAUSED. A Label in the UI shows
|
||||
messages sent from the C code (for errors and state changes).
|
||||
|
||||
# The User Interface
|
||||
## The User Interface
|
||||
|
||||
A toolbar at the bottom of the screen contains a Play and a Pause
|
||||
button. Over the toolbar there is a Label used to display messages from
|
||||
|
|
@ -50,10 +52,10 @@ GStreamer. This tutorial does not require more elements, but the
|
|||
following lessons will build their User Interfaces on top of this one,
|
||||
adding more components.
|
||||
|
||||
# The View Controller
|
||||
## The View Controller
|
||||
|
||||
The `ViewController` class manages the UI, instantiates
|
||||
the `GStreamerBackend` and also performs some UI-related tasks on its
|
||||
The `ViewController` class manages the UI, instantiates
|
||||
the `GStreamerBackend` and also performs some UI-related tasks on its
|
||||
behalf:
|
||||
|
||||
**ViewController.m**
|
||||
|
|
@ -126,7 +128,7 @@ behalf:
|
|||
@end
|
||||
```
|
||||
|
||||
An instance of the `GStreamerBackend` in stored inside the class:
|
||||
An instance of the `GStreamerBackend` in stored inside the class:
|
||||
|
||||
```
|
||||
@interface ViewController () {
|
||||
|
|
@ -134,8 +136,8 @@ An instance of the `GStreamerBackend` in stored inside the class:
|
|||
}
|
||||
```
|
||||
|
||||
This instance is created in the `viewDidLoad` function through a custom
|
||||
`init:` method in the `GStreamerBackend`:
|
||||
This instance is created in the `viewDidLoad` function through a custom
|
||||
`init:` method in the `GStreamerBackend`:
|
||||
|
||||
```
|
||||
- (void)viewDidLoad
|
||||
|
|
@ -150,11 +152,11 @@ This instance is created in the `viewDidLoad` function through a custom
|
|||
```
|
||||
|
||||
This custom method is required to pass the object that has to be used as
|
||||
the UI delegate (in this case, ourselves, the `ViewController`).
|
||||
the UI delegate (in this case, ourselves, the `ViewController`).
|
||||
|
||||
The Play and Pause buttons are also disabled in the
|
||||
`viewDidLoad` function, and they are not re-enabled until the
|
||||
`GStreamerBackend` reports that it is initialized and ready.
|
||||
`viewDidLoad` function, and they are not re-enabled until the
|
||||
`GStreamerBackend` reports that it is initialized and ready.
|
||||
|
||||
```
|
||||
/* Called when the Play button is pressed */
|
||||
|
|
@ -185,13 +187,13 @@ buttons, and simply forward the call to the appropriate method in the
|
|||
}
|
||||
```
|
||||
|
||||
The `gstreamerInitialized` method is defined in the
|
||||
`GStreamerBackendDelegate` protocol and indicates that the backend is
|
||||
The `gstreamerInitialized` method is defined in the
|
||||
`GStreamerBackendDelegate` protocol and indicates that the backend is
|
||||
ready to accept commands. In this case, the Play and Pause buttons are
|
||||
re-enabled and the Label text is set to “Ready”. This method is called
|
||||
from a Dispatch Queue other than the Main one; therefore the need for
|
||||
the
|
||||
[dispatch\_async()](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/dispatch_async.3.html) call
|
||||
[dispatch_async()](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/dispatch_async.3.html) call
|
||||
wrapping all UI code.
|
||||
|
||||
```
|
||||
|
|
@ -203,19 +205,19 @@ wrapping all UI code.
|
|||
}
|
||||
```
|
||||
|
||||
The `gstreamerSetUIMessage:` method also belongs to the
|
||||
`GStreamerBackendDelegate` protocol. It is called when the backend wants
|
||||
The `gstreamerSetUIMessage:` method also belongs to the
|
||||
`GStreamerBackendDelegate` protocol. It is called when the backend wants
|
||||
to report some message to the user. In this case, the message is copied
|
||||
onto the Label in the UI, again, from within a
|
||||
[dispatch\_async()](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/dispatch_async.3.html) call.
|
||||
[dispatch_async()](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/dispatch_async.3.html) call.
|
||||
|
||||
# The GStreamer Backend
|
||||
## The GStreamer Backend
|
||||
|
||||
The `GStreamerBackend` class performs all GStreamer-related tasks and
|
||||
The `GStreamerBackend` class performs all GStreamer-related tasks and
|
||||
offers a simplified interface to the application, which does not need to
|
||||
deal with all the GStreamer details. When it needs to perform any UI
|
||||
action, it does so through a delegate, which is expected to adhere to
|
||||
the `GStreamerBackendDelegate` protocol:
|
||||
the `GStreamerBackendDelegate` protocol:
|
||||
|
||||
**GStreamerBackend.m**
|
||||
|
||||
|
|
@ -398,7 +400,7 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
|
|||
@end
|
||||
```
|
||||
|
||||
|
||||
|
||||
|
||||
#### Interface methods:
|
||||
|
||||
|
|
@ -422,13 +424,13 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
|
|||
}
|
||||
```
|
||||
|
||||
The `init:` method creates the instance by calling `[super init]`,
|
||||
The `init:` method creates the instance by calling `[super init]`,
|
||||
stores the delegate object that will handle the UI interaction and
|
||||
launches the `app_function`, from a separate, concurrent, Dispatch
|
||||
Queue. The `app_function` monitors the GStreamer bus for messages and
|
||||
Queue. The `app_function` monitors the GStreamer bus for messages and
|
||||
warns the application when interesting things happen.
|
||||
|
||||
`init:` also registers a new GStreamer debug category and sets its
|
||||
`init:` also registers a new GStreamer debug category and sets its
|
||||
threshold, so we can see the debug output from within Xcode and keep
|
||||
track of our application progress.
|
||||
|
||||
|
|
@ -444,7 +446,7 @@ track of our application progress.
|
|||
}
|
||||
```
|
||||
|
||||
The `dealloc` method takes care of bringing the pipeline to the NULL
|
||||
The `dealloc` method takes care of bringing the pipeline to the NULL
|
||||
state and releasing it.
|
||||
|
||||
```
|
||||
|
|
@ -463,7 +465,7 @@ state and releasing it.
|
|||
}
|
||||
```
|
||||
|
||||
The `play` and `pause` methods simply try to set the pipeline to the
|
||||
The `play` and `pause` methods simply try to set the pipeline to the
|
||||
desired state and warn the application if something fails.
|
||||
|
||||
#### Private methods:
|
||||
|
|
@ -480,11 +482,11 @@ desired state and warn the application if something fails.
|
|||
}
|
||||
```
|
||||
|
||||
`setUIMessage:` turns the C strings that GStreamer uses (UTF8 `char *`)
|
||||
into `NSString *` and displays them through the
|
||||
`gstreamerSetUIMessage` method of the `GStreamerBackendDelegate`. The
|
||||
`setUIMessage:` turns the C strings that GStreamer uses (UTF8 `char *`)
|
||||
into `NSString *` and displays them through the
|
||||
`gstreamerSetUIMessage` method of the `GStreamerBackendDelegate`. The
|
||||
implementation of this method is marked as `@optional`, and hence the
|
||||
check for its existence in the delegate with `respondsToSelector:`
|
||||
check for its existence in the delegate with `respondsToSelector:`
|
||||
|
||||
```
|
||||
/* Retrieve errors from the bus and show them on the UI */
|
||||
|
|
@ -517,18 +519,18 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
|
|||
}
|
||||
```
|
||||
|
||||
The `error_cb()` and `state_changed_cb()` are callbacks registered to
|
||||
the `error` and `state-changed` events in GStreamer, and their goal is
|
||||
The `error_cb()` and `state_changed_cb()` are callbacks registered to
|
||||
the `error` and `state-changed` events in GStreamer, and their goal is
|
||||
to inform the user about these events. These callbacks have been widely
|
||||
used in the [Basic tutorials](Basic%2Btutorials.html) and their
|
||||
used in the [Basic tutorials](sdk-basic-tutorials.md) and their
|
||||
implementation is very similar, except for two points:
|
||||
|
||||
Firstly, the messages are conveyed to the user through the
|
||||
`setUIMessage:` private method discussed above.
|
||||
`setUIMessage:` private method discussed above.
|
||||
|
||||
Secondly, they require an instance of a `GStreamerBackend` object in
|
||||
Secondly, they require an instance of a `GStreamerBackend` object in
|
||||
order to call its instance method `setUIMessage:`, which is passed
|
||||
through the `userdata` pointer of the callbacks (the `self` pointer in
|
||||
through the `userdata` pointer of the callbacks (the `self` pointer in
|
||||
these implementations). This is discussed below when registering the
|
||||
callbacks in the `app_function`.
|
||||
|
||||
|
|
@ -548,14 +550,14 @@ callbacks in the `app_function`.
|
|||
}
|
||||
```
|
||||
|
||||
`check_initialization_complete()` verifies that all conditions are met
|
||||
`check_initialization_complete()` verifies that all conditions are met
|
||||
to consider the backend ready to accept commands and tell the
|
||||
application if so. In this simple tutorial the only conditions are that
|
||||
the main loop exists and that we have not already told the application
|
||||
about this fact. Later (more complex) tutorials include additional
|
||||
conditions.
|
||||
|
||||
Finally, most of the GStreamer work is performed in the app\_function.
|
||||
Finally, most of the GStreamer work is performed in the app_function.
|
||||
It exists with almost identical content in the Android tutorial, which
|
||||
exemplifies how the same code can run on both platforms with little
|
||||
change.
|
||||
|
|
@ -566,11 +568,11 @@ change.
|
|||
g_main_context_push_thread_default(context);
|
||||
```
|
||||
|
||||
It first creates a GLib context so all `GSource`s are kept in the same
|
||||
It first creates a GLib context so all `GSource`s are kept in the same
|
||||
place. This also helps cleaning after GSources created by other
|
||||
libraries which might not have been properly disposed of. A new context
|
||||
is created with `g_main_context_new()` and then it is made the default
|
||||
one for the thread with `g_main_context_push_thread_default()`.
|
||||
is created with `g_main_context_new()` and then it is made the default
|
||||
one for the thread with `g_main_context_push_thread_default()`.
|
||||
|
||||
```
|
||||
/* Build pipeline */
|
||||
|
|
@ -584,9 +586,9 @@ one for the thread with `g_main_context_push_thread_default()`.
|
|||
}
|
||||
```
|
||||
|
||||
It then creates a pipeline the easy way, with `gst_parse_launch()`. In
|
||||
this case, it is simply an `audiotestsrc` (which produces a continuous
|
||||
tone) and an `autoaudiosink`, with accompanying adapter
|
||||
It then creates a pipeline the easy way, with `gst_parse_launch()`. In
|
||||
this case, it is simply an `audiotestsrc` (which produces a continuous
|
||||
tone) and an `autoaudiosink`, with accompanying adapter
|
||||
elements.
|
||||
|
||||
```
|
||||
|
|
@ -603,11 +605,11 @@ elements.
|
|||
|
||||
These lines create a bus signal watch and connect to some interesting
|
||||
signals, just like we have been doing in the [Basic
|
||||
tutorials](Basic%2Btutorials.html). The creation of the watch is done
|
||||
step by step instead of using `gst_bus_add_signal_watch()` to exemplify
|
||||
tutorials](sdk-basic-tutorials.md). The creation of the watch is done
|
||||
step by step instead of using `gst_bus_add_signal_watch()` to exemplify
|
||||
how to use a custom GLib context. The interesting bit here is the usage
|
||||
of a
|
||||
[\_\_bridge](http://clang.llvm.org/docs/AutomaticReferenceCounting.html#bridged-casts)
|
||||
[__bridge](http://clang.llvm.org/docs/AutomaticReferenceCounting.html#bridged-casts)
|
||||
cast to convert an Objective-C object into a plain C pointer. In this
|
||||
case we do not worry much about transferal of ownership of the object,
|
||||
because it travels through C-land untouched. It re-emerges at the
|
||||
|
|
@ -626,38 +628,32 @@ different callbacks through the userdata pointer and cast again to a
|
|||
```
|
||||
|
||||
Finally, the main loop is created and set to run. Before entering the
|
||||
main loop, though, `check_initialization_complete()` is called. Upon
|
||||
main loop, though, `check_initialization_complete()` is called. Upon
|
||||
exit, the main loop is disposed of.
|
||||
|
||||
And this is it\! This has been a rather long tutorial, but we covered a
|
||||
And this is it! This has been a rather long tutorial, but we covered a
|
||||
lot of territory. Building on top of this one, the following ones are
|
||||
shorter and focus only on the new topics.
|
||||
|
||||
# Conclusion
|
||||
## Conclusion
|
||||
|
||||
This tutorial has shown:
|
||||
|
||||
- How to handle GStreamer code from a separate thread using a
|
||||
[Dispatch
|
||||
Queue](http://developer.apple.com/library/ios/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html) other
|
||||
Queue](http://developer.apple.com/library/ios/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html) other
|
||||
than the Main one.
|
||||
- How to pass objects between the Objective-C UI code and the C
|
||||
GStreamer code.
|
||||
|
||||
Most of the methods introduced in this tutorial,
|
||||
like `check_initialization_complete()`and `app_function()`, and the
|
||||
interface methods `init:`, `play:`, `pause:`,
|
||||
`gstreamerInitialized:` and `setUIMessage:` will continue to be used in
|
||||
like `check_initialization_complete()`and `app_function()`, and the
|
||||
interface methods `init:`, `play:`, `pause:`,
|
||||
`gstreamerInitialized:` and `setUIMessage:` will continue to be used in
|
||||
the following tutorials with minimal modifications, so better get used
|
||||
to them\!
|
||||
to them!
|
||||
|
||||
It has been a pleasure having you here, and see you soon\!
|
||||
It has been a pleasure having you here, and see you soon!
|
||||
|
||||
## Attachments:
|
||||
|
||||
|
||||
[ios-tutorial2-screenshot.png](attachments/3571718/3538954.png)
|
||||
(image/png)
|
||||
|
||||
[ios-tutorial2-screenshot.png](attachments/3571718/3538953.png)
|
||||
(image/png)
|
||||
[screenshot]: images/sdk-ios-tutorial-a-running-pipeline-screenshot.png
|
||||
|
|
@ -1,30 +1,31 @@
|
|||
# iOS tutorial 1: Link against GStreamer
|
||||
|
||||
# Goal
|
||||
## Goal
|
||||
|
||||
![screenshot]
|
||||
|
||||
The first iOS tutorial is simple. The objective is to get the GStreamer
|
||||
version and display it on screen. It exemplifies how to link against the
|
||||
GStreamer library from Xcode using objective-C.
|
||||
|
||||
# Hello GStreamer\!
|
||||
## Hello GStreamer!
|
||||
|
||||
The code for this project can be found in the tutorials folder of your
|
||||
GStreamer SDK iOS installation. It was created using the GStreamer
|
||||
Single View Application template. The view contains only a
|
||||
`UILabel` that will be used to display the GStreamer's version to the
|
||||
user.
|
||||
The code for this project can be found in the tutorials folder of
|
||||
**FIXME: where**. It was created using the GStreamer Single View
|
||||
Application template. The view contains only a `UILabel` that will be
|
||||
used to display the GStreamer's version to the user.
|
||||
|
||||
# The User Interface
|
||||
## The User Interface
|
||||
|
||||
The UI uses storyboards and contains a single `View` with a centered
|
||||
`UILabel`. The `ViewController` for the `View` links its
|
||||
`label` variable to this `UILabel` as an `IBOutlet`.
|
||||
The UI uses storyboards and contains a single `View` with a centered
|
||||
`UILabel`. The `ViewController` for the `View` links its
|
||||
`label` variable to this `UILabel` as an `IBOutlet`.
|
||||
|
||||
**ViewController.h**
|
||||
|
||||
```
|
||||
#import <UIKit/UIKit.h>
|
||||
|
||||
|
||||
@interface ViewController : UIViewController {
|
||||
IBOutlet UILabel *label;
|
||||
}
|
||||
|
|
@ -34,18 +35,18 @@ The UI uses storyboards and contains a single `View` with a centered
|
|||
@end
|
||||
```
|
||||
|
||||
# The GStreamer backend
|
||||
## The GStreamer backend
|
||||
|
||||
All GStreamer-handling code is kept in a single Objective-C class called
|
||||
`GStreamerBackend`. In successive tutorials it will get expanded, but,
|
||||
for now, it only contains a method to retrieve the GStreamer version.
|
||||
|
||||
The `GStreamerBackend` is made in Objective-C so it can take care of the
|
||||
The `GStreamerBackend` is made in Objective-C so it can take care of the
|
||||
few C-to-Objective-C conversions that might be necessary (like `char
|
||||
*` to `NSString *`, for example). This eases the usage of this class by
|
||||
*` to `NSString *`, for example). This eases the usage of this class by
|
||||
the UI code, which is typically made in pure Objective-C.
|
||||
`GStreamerBackend` serves exactly the same purpose as the JNI code in
|
||||
the [Android tutorials](Android%2Btutorials.html).
|
||||
`GStreamerBackend` serves exactly the same purpose as the JNI code in
|
||||
the [](sdk-android-tutorials.md).
|
||||
|
||||
**GStreamerBackend.m**
|
||||
|
||||
|
|
@ -67,19 +68,19 @@ the [Android tutorials](Android%2Btutorials.html).
|
|||
@end
|
||||
```
|
||||
|
||||
The `getGStreamerVersion()` method simply calls
|
||||
`gst_version_string()` to obtain a string describing this version of
|
||||
GStreamer. This [Modified
|
||||
UTF8](http://en.wikipedia.org/wiki/UTF-8#Modified_UTF-8) string is then
|
||||
converted to a `NSString *` by ` NSString:stringWithUTF8String `and
|
||||
The `getGStreamerVersion()` method simply calls
|
||||
`gst_version_string()` to obtain a string describing this version of
|
||||
GStreamer. This [Modified
|
||||
UTF8](http://en.wikipedia.org/wiki/UTF-8#Modified_UTF-8) string is then
|
||||
converted to a `NSString *` by ` NSString:stringWithUTF8String `and
|
||||
returned. Objective-C will take care of freeing the memory used by the
|
||||
new `NSString *`, but we need to free the `char *` returned
|
||||
by `gst_version_string()`.
|
||||
new `NSString *`, but we need to free the `char *` returned
|
||||
by `gst_version_string()`.
|
||||
|
||||
# The View Controller
|
||||
## The View Controller
|
||||
|
||||
The view controller instantiates the GStremerBackend and asks it for the
|
||||
GStreamer version to display at the label. That's it\!
|
||||
GStreamer version to display at the label. That's it!
|
||||
|
||||
**ViewController.m**
|
||||
|
||||
|
|
@ -115,28 +116,18 @@ GStreamer version to display at the label. That's it\!
|
|||
@end
|
||||
```
|
||||
|
||||
# Conclusion
|
||||
## Conclusion
|
||||
|
||||
This ends the first iOS tutorial. It has shown that, due to the
|
||||
compatibility of C and Objective-C, adding GStreamer support to an iOS
|
||||
compatibility of C and Objective-C, adding GStreamer support to an iOS
|
||||
app is as easy as it is on a Desktop application. An extra Objective-C
|
||||
wrapper has been added (the `GStreamerBackend` class) for clarity, but
|
||||
wrapper has been added (the `GStreamerBackend` class) for clarity, but
|
||||
calls to the GStreamer framework are valid from any part of the
|
||||
application code.
|
||||
|
||||
The following tutorials detail the few places in which care has to be
|
||||
taken when developing specifically for the iOS platform.
|
||||
|
||||
It has been a pleasure having you here, and see you soon\!
|
||||
It has been a pleasure having you here, and see you soon!
|
||||
|
||||
## Attachments:
|
||||
|
||||
|
||||
[ios-tutorial1-screenshot.png](attachments/3014792/3113602.png)
|
||||
(image/png)
|
||||
|
||||
[ios-tutorial1-screenshot.png](attachments/3014792/3113603.png)
|
||||
(image/png)
|
||||
|
||||
[ios-tutorial1-screenshot.png](attachments/3014792/3113601.png)
|
||||
(image/png)
|
||||
[screenshot]: images/sdk-ios-tutorial-link-against-gstreamer-screenshot.png
|
||||
|
|
@ -1,9 +1,10 @@
|
|||
# iOS tutorial 3: Video
|
||||
|
||||
# Goal
|
||||
# Goal
|
||||
|
||||
Except for [Basic tutorial 5: GUI toolkit
|
||||
integration](Basic%2Btutorial%2B5%253A%2BGUI%2Btoolkit%2Bintegration.html),
|
||||
![screenshot]
|
||||
|
||||
Except for [](sdk-basic-tutorial-toolkit-integration.md),
|
||||
which embedded a video window on a GTK application, all tutorials so far
|
||||
relied on GStreamer video sinks to create a window to display their
|
||||
contents. The video sink on iOS is not capable of creating its own
|
||||
|
|
@ -17,24 +18,23 @@ shows:
|
|||
|
||||
Since iOS does not provide a windowing system, a GStreamer video sink
|
||||
cannot create pop-up windows as it would do on a Desktop platform.
|
||||
Fortunately, the `XOverlay` interface allows providing video sinks with
|
||||
Fortunately, the `VideoOverlay` interface allows providing video sinks with
|
||||
an already created window onto which they can draw, as we have seen
|
||||
in [Basic tutorial 5: GUI toolkit
|
||||
integration](Basic%2Btutorial%2B5%253A%2BGUI%2Btoolkit%2Bintegration.html).
|
||||
in [](sdk-basic-tutorial-toolkit-integration.md).
|
||||
|
||||
In this tutorial, a `UIView` widget (actually, a subclass of it) is
|
||||
placed on the main storyboard. In the `viewDidLoad` method of the
|
||||
`ViewController`, we pass a pointer to this `UIView `to the instance of
|
||||
In this tutorial, a `UIView` widget (actually, a subclass of it) is
|
||||
placed on the main storyboard. In the `viewDidLoad` method of the
|
||||
`ViewController`, we pass a pointer to this `UIView `to the instance of
|
||||
the `GStreamerBackend`, so it can tell the video sink where to draw.
|
||||
|
||||
# The User Interface
|
||||
|
||||
The storyboard from the previous tutorial is expanded: A `UIView `is
|
||||
The storyboard from the previous tutorial is expanded: A `UIView `is
|
||||
added over the toolbar and pinned to all sides so it takes up all
|
||||
available space (`video_container_view` outlet). Inside it, another
|
||||
`UIView `is added (`video_view` outlet) which contains the actual video,
|
||||
`UIView `is added (`video_view` outlet) which contains the actual video,
|
||||
centered to its parent, and with a size that adapts to the media size
|
||||
(through the `video_width_constraint` and `video_height_constraint`
|
||||
(through the `video_width_constraint` and `video_height_constraint`
|
||||
outlets):
|
||||
|
||||
**ViewController.h**
|
||||
|
|
@ -65,8 +65,8 @@ outlets):
|
|||
|
||||
# The View Controller
|
||||
|
||||
The `ViewController `class manages the UI, instantiates
|
||||
the `GStreamerBackend` and also performs some UI-related tasks on its
|
||||
The `ViewController `class manages the UI, instantiates
|
||||
the `GStreamerBackend` and also performs some UI-related tasks on its
|
||||
behalf:
|
||||
|
||||
**ViewController.m**
|
||||
|
|
@ -193,12 +193,12 @@ media is constant and initialized in `viewDidLoad`:
|
|||
}
|
||||
```
|
||||
|
||||
As shown below, the `GStreamerBackend` constructor has also been
|
||||
expanded to accept another parameter: the `UIView *` where the video
|
||||
As shown below, the `GStreamerBackend` constructor has also been
|
||||
expanded to accept another parameter: the `UIView *` where the video
|
||||
sink should draw.
|
||||
|
||||
The rest of the `ViewController `code is the same as the previous
|
||||
tutorial, except for the code that adapts the `video_view` size to the
|
||||
The rest of the `ViewController `code is the same as the previous
|
||||
tutorial, except for the code that adapts the `video_view` size to the
|
||||
media size, respecting its aspect ratio:
|
||||
|
||||
```
|
||||
|
|
@ -220,11 +220,11 @@ media size, respecting its aspect ratio:
|
|||
}
|
||||
```
|
||||
|
||||
The `viewDidLayoutSubviews` method is called every time the main view
|
||||
The `viewDidLayoutSubviews` method is called every time the main view
|
||||
size has changed (for example, due to a device orientation change) and
|
||||
the entire layout has been recalculated. At this point, we can access
|
||||
the `bounds` property of the `video_container_view` to retrieve its new
|
||||
size and change the `video_view` size accordingly.
|
||||
the `bounds` property of the `video_container_view` to retrieve its new
|
||||
size and change the `video_view` size accordingly.
|
||||
|
||||
The simple algorithm above maximizes either the width or the height of
|
||||
the `video_view`, while changing the other axis so the aspect ratio of
|
||||
|
|
@ -233,18 +233,18 @@ with a surface of the correct proportions, so it does not need to add
|
|||
black borders (*letterboxing*), which is a waste of processing power.
|
||||
|
||||
The final size is reported to the layout engine by changing the
|
||||
`constant` field in the width and height `Constraints` of the
|
||||
`constant` field in the width and height `Constraints` of the
|
||||
`video_view`. These constraints have been created in the storyboard and
|
||||
are accessible to the `ViewController `through IBOutlets, as is usually
|
||||
are accessible to the `ViewController `through IBOutlets, as is usually
|
||||
done with other widgets.
|
||||
|
||||
# The GStreamer Backend
|
||||
|
||||
The `GStreamerBackend` class performs all GStreamer-related tasks and
|
||||
The `GStreamerBackend` class performs all GStreamer-related tasks and
|
||||
offers a simplified interface to the application, which does not need to
|
||||
deal with all the GStreamer details. When it needs to perform any UI
|
||||
action, it does so through a delegate, which is expected to adhere to
|
||||
the `GStreamerBackendDelegate` protocol:
|
||||
the `GStreamerBackendDelegate` protocol:
|
||||
|
||||
**GStreamerBackend.m**
|
||||
|
||||
|
|
@ -252,7 +252,7 @@ the `GStreamerBackendDelegate` protocol:
|
|||
#import "GStreamerBackend.h"
|
||||
|
||||
#include <gst/gst.h>
|
||||
#include <gst/interfaces/xoverlay.h>
|
||||
#include <gst/video/video.h>
|
||||
|
||||
GST_DEBUG_CATEGORY_STATIC (debug_category);
|
||||
#define GST_CAT_DEFAULT debug_category
|
||||
|
|
@ -266,7 +266,7 @@ GST_DEBUG_CATEGORY_STATIC (debug_category);
|
|||
@implementation GStreamerBackend {
|
||||
id ui_delegate; /* Class that we use to interact with the user interface */
|
||||
GstElement *pipeline; /* The running pipeline */
|
||||
GstElement *video_sink;/* The video sink element which receives XOverlay commands */
|
||||
GstElement *video_sink;/* The video sink element which receives VideoOverlay commands */
|
||||
GMainContext *context; /* GLib context used to run the main loop */
|
||||
GMainLoop *main_loop; /* GLib main loop */
|
||||
gboolean initialized; /* To avoid informing the UI multiple times about the initialization */
|
||||
|
|
@ -391,7 +391,7 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
|
|||
g_main_context_push_thread_default(context);
|
||||
|
||||
/* Build pipeline */
|
||||
pipeline = gst_parse_launch("videotestsrc ! warptv ! ffmpegcolorspace ! autovideosink", &error);
|
||||
pipeline = gst_parse_launch("videotestsrc ! warptv ! videoconvert ! autovideosink", &error);
|
||||
if (error) {
|
||||
gchar *message = g_strdup_printf("Unable to build pipeline: %s", error->message);
|
||||
g_clear_error (&error);
|
||||
|
|
@ -403,12 +403,12 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
|
|||
/* Set the pipeline to READY, so it can already accept a window handle */
|
||||
gst_element_set_state(pipeline, GST_STATE_READY);
|
||||
|
||||
video_sink = gst_bin_get_by_interface(GST_BIN(pipeline), GST_TYPE_X_OVERLAY);
|
||||
video_sink = gst_bin_get_by_interface(GST_BIN(pipeline), GST_TYPE_VIDEO_OVERLAY);
|
||||
if (!video_sink) {
|
||||
GST_ERROR ("Could not retrieve video sink");
|
||||
return;
|
||||
}
|
||||
gst_x_overlay_set_window_handle(GST_X_OVERLAY(video_sink), (guintptr) (id) ui_video_view);
|
||||
gst_video_overlay_set_window_handle(GST_VIDEO_OVERLAY(video_sink), (guintptr) (id) ui_video_view);
|
||||
|
||||
/* Instruct the bus to emit signals for each received message, and connect to the interesting signals */
|
||||
bus = gst_element_get_bus (pipeline);
|
||||
|
|
@ -442,13 +442,13 @@ static void state_changed_cb (GstBus *bus, GstMessage *msg, GStreamerBackend *se
|
|||
```
|
||||
|
||||
The main differences with the previous tutorial are related to the
|
||||
handling of the `XOverlay` interface:
|
||||
handling of the `VideoOverlay` interface:
|
||||
|
||||
```
|
||||
@implementation GStreamerBackend {
|
||||
id ui_delegate; /* Class that we use to interact with the user interface */
|
||||
GstElement *pipeline; /* The running pipeline */
|
||||
GstElement *video_sink;/* The video sink element which receives XOverlay commands */
|
||||
GstElement *video_sink;/* The video sink element which receives VideoOverlay commands */
|
||||
GMainContext *context; /* GLib context used to run the main loop */
|
||||
GMainLoop *main_loop; /* GLib main loop */
|
||||
gboolean initialized; /* To avoid informing the UI multiple times about the initialization */
|
||||
|
|
@ -457,7 +457,7 @@ handling of the `XOverlay` interface:
|
|||
```
|
||||
|
||||
The class is expanded to keep track of the video sink element in the
|
||||
pipeline and the `UIView *` onto which rendering is to occur.
|
||||
pipeline and the `UIView *` onto which rendering is to occur.
|
||||
|
||||
```
|
||||
-(id) init:(id) uiDelegate videoView:(UIView *)video_view
|
||||
|
|
@ -480,62 +480,61 @@ pipeline and the `UIView *` onto which rendering is to occur.
|
|||
}
|
||||
```
|
||||
|
||||
The constructor accepts the `UIView *` as a new parameter, which, at
|
||||
The constructor accepts the `UIView *` as a new parameter, which, at
|
||||
this point, is simply remembered in `ui_video_view`.
|
||||
|
||||
```
|
||||
/* Build pipeline */
|
||||
pipeline = gst_parse_launch("videotestsrc ! warptv ! ffmpegcolorspace ! autovideosink", &error);
|
||||
pipeline = gst_parse_launch("videotestsrc ! warptv ! videoconvert ! autovideosink", &error);
|
||||
```
|
||||
|
||||
Then, in the `app_function`, the pipeline is constructed. This time we
|
||||
build a video pipeline using a simple `videotestsrc` element with a
|
||||
`warptv` to add some spice. The video sink is `autovideosink`, which
|
||||
build a video pipeline using a simple `videotestsrc` element with a
|
||||
`warptv` to add some spice. The video sink is `autovideosink`, which
|
||||
choses the appropriate sink for the platform (currently,
|
||||
`eglglessink` is the only option for
|
||||
`glimagesink` is the only option for
|
||||
iOS).
|
||||
|
||||
```
|
||||
/* Set the pipeline to READY, so it can already accept a window handle */
|
||||
gst_element_set_state(pipeline, GST_STATE_READY);
|
||||
|
||||
video_sink = gst_bin_get_by_interface(GST_BIN(pipeline), GST_TYPE_X_OVERLAY);
|
||||
video_sink = gst_bin_get_by_interface(GST_BIN(pipeline), GST_TYPE_VIDEO_OVERLAY);
|
||||
if (!video_sink) {
|
||||
GST_ERROR ("Could not retrieve video sink");
|
||||
return;
|
||||
}
|
||||
gst_x_overlay_set_window_handle(GST_X_OVERLAY(video_sink), (guintptr) (id) ui_video_view);
|
||||
gst_video_overlay_set_window_handle(GST_VIDEO_OVERLAY(video_sink), (guintptr) (id) ui_video_view);
|
||||
```
|
||||
|
||||
Once the pipeline is built, we set it to READY. In this state, dataflow
|
||||
has not started yet, but the caps of adjacent elements have been
|
||||
verified to be compatible and their pads have been linked. Also, the
|
||||
`autovideosink` has already instantiated the actual video sink so we can
|
||||
`autovideosink` has already instantiated the actual video sink so we can
|
||||
ask for it immediately.
|
||||
|
||||
The `gst_bin_get_by_interface()` method will examine the whole pipeline
|
||||
The `gst_bin_get_by_interface()` method will examine the whole pipeline
|
||||
and return a pointer to an element which supports the requested
|
||||
interface. We are asking for the `XOverlay` interface, explained in
|
||||
[Basic tutorial 5: GUI toolkit
|
||||
integration](Basic%2Btutorial%2B5%253A%2BGUI%2Btoolkit%2Bintegration.html),
|
||||
interface. We are asking for the `VideoOverlay` interface, explained in
|
||||
[](sdk-basic-tutorial-toolkit-integration.md),
|
||||
which controls how to perform rendering into foreign (non-GStreamer)
|
||||
windows. The internal video sink instantiated by `autovideosink` is the
|
||||
windows. The internal video sink instantiated by `autovideosink` is the
|
||||
only element in this pipeline implementing it, so it will be returned.
|
||||
|
||||
Once we have the video sink, we inform it of the `UIView` to use for
|
||||
rendering, through the `gst_x_overlay_set_window_handle()` method.
|
||||
Once we have the video sink, we inform it of the `UIView` to use for
|
||||
rendering, through the `gst_video_overlay_set_window_handle()` method.
|
||||
|
||||
# EaglUIView
|
||||
|
||||
One last detail remains. In order for `eglglessink` to be able to draw
|
||||
One last detail remains. In order for `glimagesink` to be able to draw
|
||||
on the
|
||||
[`UIView`](http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIView_Class/UIView/UIView.html),
|
||||
the
|
||||
[`Layer`](http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Reference/CALayer_class/Introduction/Introduction.html#//apple_ref/occ/cl/CALayer) associated
|
||||
[`Layer`](http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Reference/CALayer_class/Introduction/Introduction.html#//apple_ref/occ/cl/CALayer) associated
|
||||
with this view must be of the
|
||||
[`CAEAGLLayer`](http://developer.apple.com/library/ios/#documentation/QuartzCore/Reference/CAEAGLLayer_Class/CAEGLLayer/CAEGLLayer.html#//apple_ref/occ/cl/CAEAGLLayer) class.
|
||||
To this avail, we create the `EaglUIView` class, derived from
|
||||
`UIView `and overriding the `layerClass` method:
|
||||
[`CAEAGLLayer`](http://developer.apple.com/library/ios/#documentation/QuartzCore/Reference/CAEAGLLayer_Class/CAEGLLayer/CAEGLLayer.html#//apple_ref/occ/cl/CAEAGLLayer) class.
|
||||
To this avail, we create the `EaglUIView` class, derived from
|
||||
`UIView `and overriding the `layerClass` method:
|
||||
|
||||
**EaglUIView.m**
|
||||
|
||||
|
|
@ -554,9 +553,9 @@ To this avail, we create the `EaglUIView` class, derived from
|
|||
@end
|
||||
```
|
||||
|
||||
When creating storyboards, bear in mind that the `UIView `which should
|
||||
contain the video must have `EaglUIView` as its custom class. This is
|
||||
easy to setup from the Xcode interface builder. Take a look at the
|
||||
When creating storyboards, bear in mind that the `UIView `which should
|
||||
contain the video must have `EaglUIView` as its custom class. This is
|
||||
easy to setup from the Xcode interface builder. Take a look at the
|
||||
tutorial storyboard to see how to achieve this.
|
||||
|
||||
And this is it, using GStreamer to output video onto an iOS application
|
||||
|
|
@ -566,18 +565,14 @@ is as simple as it seems.
|
|||
|
||||
This tutorial has shown:
|
||||
|
||||
- How to display video on iOS using a `UIView `and
|
||||
the `XOverlay` interface.
|
||||
- How to display video on iOS using a `UIView `and
|
||||
the `VideoOverlay` interface.
|
||||
- How to report the media size to the iOS layout engine through
|
||||
runtime manipulation of width and height constraints.
|
||||
|
||||
The following tutorial plays an actual clip and adds a few more controls
|
||||
to this tutorial in order to build a simple media player.
|
||||
|
||||
It has been a pleasure having you here, and see you soon\!
|
||||
It has been a pleasure having you here, and see you soon!
|
||||
|
||||
## Attachments:
|
||||
|
||||
|
||||
[ios-tutorial3-screenshot.png](attachments/3571736/3538955.png)
|
||||
(image/png)
|
||||
[screenshot]: images/sdk-ios-tutorial-video-screenshot.png
|
||||
|
|
@ -1,34 +1,32 @@
|
|||
# iOS tutorials
|
||||
|
||||
# Welcome to the GStreamer SDK iOS tutorials
|
||||
## Welcome to the GStreamer SDK iOS tutorials
|
||||
|
||||
These tutorials describe iOS-specific topics. General GStreamer concepts
|
||||
will not be explained in these tutorials, so the [Basic
|
||||
tutorials](http://docs.gstreamer.com/display/GstSDK/Basic+tutorials) should
|
||||
be reviewed first. The reader should also be familiar with basic iOS
|
||||
programming techniques.
|
||||
These tutorials describe iOS-specific topics. General GStreamer
|
||||
concepts will not be explained in these tutorials, so the
|
||||
[](sdk-basic-tutorials.md) should be reviewed first. The reader should
|
||||
also be familiar with basic iOS programming techniques.
|
||||
|
||||
The iOS tutorials have the same structure as the [Android
|
||||
tutorials](Android%2Btutorials.html): Each one builds on top of the
|
||||
previous one and adds progressively more functionality, until a working
|
||||
media player application is obtained in [iOS tutorial 5: A Complete
|
||||
media
|
||||
player](http://docs.gstreamer.com/display/GstSDK/iOS+tutorial+5%3A+A+Complete+media+player).
|
||||
The iOS tutorials have the same structure as the
|
||||
[](sdk-android-tutorials.md): Each one builds on top of the previous
|
||||
one and adds progressively more functionality, until a working media
|
||||
player application is obtained in
|
||||
[](sdk-ios-tutorial-a-complete-media-player.md).
|
||||
|
||||
Make sure to have read the instructions in [Installing for iOS
|
||||
development](Installing%2Bfor%2BiOS%2Bdevelopment.html) before jumping
|
||||
into the iOS tutorials.
|
||||
Make sure to have read the instructions in
|
||||
[](sdk-installing-for-ios-development.md) before jumping into the iOS
|
||||
tutorials.
|
||||
|
||||
All iOS tutorials are split into the following classes:
|
||||
|
||||
- The `GStreamerBackend` class performs all GStreamer-related tasks
|
||||
- The `GStreamerBackend` class performs all GStreamer-related tasks
|
||||
and offers a simplified interface to the application, which does not
|
||||
need to deal with all the GStreamer details. When it needs to
|
||||
perform any UI action, it does so through a delegate, which is
|
||||
expected to adhere to the `GStreamerBackendDelegate` protocol.
|
||||
- The `ViewController` class manages the UI, instantiates the
|
||||
`GStreamerBackend` and also performs some UI-related tasks on its
|
||||
expected to adhere to the `GStreamerBackendDelegate` protocol.
|
||||
- The `ViewController` class manages the UI, instantiates the
|
||||
`GStreamerBackend` and also performs some UI-related tasks on its
|
||||
behalf.
|
||||
- The `GStreamerBackendDelegate` protocol defines which methods a
|
||||
- The `GStreamerBackendDelegate` protocol defines which methods a
|
||||
class can implement in order to serve as a UI delegate for the
|
||||
`GStreamerBackend`.
|
||||
|
|
|
|||
Loading…
Reference in a new issue