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190 lines
6 KiB
Markdown
190 lines
6 KiB
Markdown
# Using GStreamer
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## Ok, I've installed GStreamer. What can I do next?
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First of all, verify that you have a working installation and that
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you can inspect plugins by typing
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```
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$ gst-inspect-1.0 fakesrc
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```
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This should print out a bunch of information about this particular
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element. If this tells you that there is "no such element or plugin",
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you haven't installed GStreamer correctly. Please check [how to get
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GStreamer](#chapter-getting) If this fails with any other message, we
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would appreciate a [bug report](#using-bugs-where).
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It's time to try out a few things. Start with gst-launch and two
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plug-ins that you really should have : fakesrc and fakesink. They do
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nothing except pass empty buffers. Type this at the command-line:
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```
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$ gst-launch-1.0 -v fakesrc silent=false num-buffers=3 ! fakesink silent=false
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```
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This will print out output that looks similar to this:
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```
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RUNNING pipeline ...
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fakesrc0: last-message = "get ******* (fakesrc0:src)gt; (0 bytes, 0) 0x8057510"
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fakesink0: last-message = "chain ******* (fakesink0:sink)lt; (0 bytes, 0) 0x8057510"
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fakesrc0: last-message = "get ******* (fakesrc0:src)gt; (0 bytes, 1) 0x8057510"
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fakesink0: last-message = "chain ******* (fakesink0:sink)lt; (0 bytes, 1) 0x8057510"
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fakesrc0: last-message = "get ******* (fakesrc0:src)gt; (0 bytes, 2) 0x8057510"
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fakesink0: last-message = "chain ******* (fakesink0:sink)lt; (0 bytes, 2) 0x8057510"
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execution ended after 5 iterations (sum 301479000 ns, average 60295800 ns, min 3000 ns, max 105482000 ns)
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```
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(Some parts of output have been removed for clarity) If it looks
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similar, then GStreamer itself is running correctly.
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To get a test video displayed, try:
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```
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$ gst-launch-1.0 videotestsrc ! videoconvert ! autovideosink
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```
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If `autovideosink` doesn't work, try an element that's specific for your
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operating system and windowing system, such as `ximagesink` or `glimagesink`
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or (on windows) `d3dvideosink`.
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## Can my system play sound through GStreamer?
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You can test this by trying to play a sine tone. For this, you
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need to link the audiotestsrc element to an output element that matches
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your hardware. A (non-complete) list of output plug-ins for audio is
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- `pulsesink` for Pulseaudio output
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- `alsasink` for ALSA output
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- `osssink` and `oss4sink` for OSS/OSSv4 output
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- `jackaudiosink` for JACK output
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- `autoaudiosink` for automatic audio output selection
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First of all, run gst-inspect-1.0 on the output plug-in you want to use
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to make sure you have it installed. For example, if you use Pulseaudio,
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run
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```
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$ gst-inspect-1.0 pulsesink
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```
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and see if that prints out a bunch of properties for the plug-in.
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Then try to play the sine tone by
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running
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```
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$ gst-launch-1.0 audiotestsrc ! audioconvert ! audioresample ! pulsesink
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```
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and see if you hear something. Make sure your volume is turned up, but
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also make sure it is not too loud and you are not wearing your
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headphones.
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## How can I see what GStreamer plugins I have on my system?
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To do this you use the gst-inspect command-line tool, which comes
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standard with GStreamer. Invoked without any arguments,
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```
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$ gst-inspect-1.0
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```
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will print out a listing of installed plugins. To learn more about a
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particular plugin, pass its name on the command line. For example,
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```
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$ gst-inspect-1.0 volume
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```
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will give you information about the volume plugin.
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## Where should I report issues?
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Issues are tracked in Freedesktop.org's Gitlab at
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<https://gitlab.freedesktop.org/gstreamer>. Using Gitlab you can view past
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issues, report new issues, submit merge requests etc. Gitlab requires you to
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create an account there, which might seem cumbersome, but allows us to at least
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have a chance at contacting you for further information, as we will often have
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to do.
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## How should I report bugs?
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When doing a bug report, you should at least describe
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- your distribution, distribution version and GStreamer version
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- how you installed GStreamer (from git, source, packages, which?)
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- if you installed GStreamer before
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If the application you are having problems with is segfaulting, then
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provide us with the necessary gdb output. See
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[???](#troubleshooting-segfault)
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## How do I use the GStreamer command line interface?
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You access the GStreamer command line interface using the command
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`gst-launch-1.0`. For example, to play a file you could just use
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```
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gst-launch-1.0 playbin uri=file:///path/to/song.mp3
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```
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You can also use `gst-play`:
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```
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gst-play-1.0 song.mp3
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```
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To decode an mp3 audio file and play it through Pulseaudio, you could use:
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```
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gst-launch-1.0 filesrc location=thesong.mp3 ! mpegaudioparse ! mpg123audiodec ! audioconvert ! pulsesink
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```
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To automatically detect and select the right decoder for a given encoded stream
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in a pipeline, try any of the following:
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```
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gst-launch-1.0 filesrc location=thesong.mp3 ! decodebin ! audioconvert ! pulsesink
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```
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```
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gst-launch-1.0 filesrc location=my-random-media-file.mpeg ! decodebin ! pulsesink
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```
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```
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gst-launch-1.0 filesrc location=my-random-media-file.mpeg ! decodebin ! videoconvert ! xvimagesink
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```
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Or even something more complicated like:
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```
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gst-launch-1.0 filesrc location=my-random-media-file.mpeg !decodebin name=decoder \
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decoder. ! queue ! videoconvert ! xvimagesink \
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decoder. ! queue ! audioconvert ! pulsesink
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```
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Building from the previous example, you can let GStreamer select an appropriate
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set of default sinks by replacing the specific output elements with these automatic
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alternatives:
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```
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gst-launch-1.0 filesrc location=my-random-media-file.mpeg !decodebin name=decoder \
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decoder. ! queue ! videoconvert ! autovideosink \
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decoder. ! queue ! audioconvert ! autoaudiosink
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```
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GStreamer also provides `playbin`, a basic media-playback plugin that
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automatically takes care of most playback details. The following example shows
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how to play any file as long as its format is supported, ie. you have the
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necessary demuxing and decoding plugins installed:
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```
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gst-launch-1.0 playbin uri=file:///home/joe/my-random-media-file.mpeg
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```
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Additional examples can be found in the `gst-launch` manual page.
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