mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-12-22 16:26:39 +00:00
73 lines
2.9 KiB
Text
73 lines
2.9 KiB
Text
=== Camerabin2 Source Requirements (draft) ===
|
|
|
|
This small document contains a collection of notes on different requirements
|
|
of a camerabin2 source element.
|
|
|
|
|
|
-- General --
|
|
It is recommended that camerabin2 source elements inherit from basecamerasrc
|
|
from gst-plugins-bad.
|
|
|
|
|
|
-- Pads --
|
|
Camerabin2 sources must have 3 static pads named 'vfsrc', 'imgsrc' and
|
|
'vidsrc'.
|
|
|
|
From an external point of view, all 3 pads work independently and camerabin2
|
|
makes no assumptions about relations about them (caps they can produce, or if
|
|
the same buffer is pushed to 2 different pads).
|
|
|
|
'vfsrc' is the pad where the viewfinder buffers should be pushed, it will
|
|
be feeding a video sink. This is the same scenario as a 'regular' source
|
|
feeding a video sink. Buffers should be continuously pushed on this pad.
|
|
|
|
'imgsrc' is the pad where image capture buffers are pushed. Timestamps aren't
|
|
really important here as the images are going to be encoded and saved
|
|
separately from each other. For each capture in image mode, one buffer should
|
|
be pushed on this pad.
|
|
|
|
'vidsrc' is the pad where video capture buffers are pushed. Once capture is
|
|
started, buffers should start being pushed on this pad until the capture is
|
|
stopped.
|
|
-> TODO - define how segments/timestamps should work here
|
|
-> TODO - How to make audio and video sync properly
|
|
|
|
|
|
-- Capture --
|
|
The sources should have a 'mode' property that informs the source of the
|
|
current capturing mode. The available options are image or video.
|
|
|
|
There are 2 signals that should be implemented, start-capture and
|
|
stop-capture, they take no arguments.
|
|
|
|
On image mode, start-capture tells the source to push an image capture
|
|
buffer on its imgsrc pad. For video mode, start-capture tells the source
|
|
to start pushing buffers on the vidsrc pad, it should only stop
|
|
pushing when a stop-capture signal is received. In either case, it is
|
|
recommended that the viewfinder pad keeps pushing buffers so the user
|
|
has a smooth experience.
|
|
|
|
Note that basecamerasrc already has the mode property and start/stop-capture
|
|
signals. It has functions that should be overridden by its child classes to
|
|
implement the handling of these actions.
|
|
|
|
|
|
-- Previews --
|
|
Camerabin2 sources must have a post-previews boolean property that the user
|
|
can select if we wants or not preview images.
|
|
|
|
Previews are posted on the bus as custom 'preview-image' messages. This message
|
|
must have a 'buffer' field that contains a GstBuffer, the preview.
|
|
|
|
Additionally, there should be a preview-caps property that is used to inform the
|
|
camera source what is the expected format of the preview image.
|
|
|
|
A preview image should be posted for each capture.
|
|
|
|
|
|
-- Negotiation --
|
|
Capture caps selection on camerabin2 works just like gstreamer's default
|
|
caps negotiation. Camerabin2 puts capsfilters downstream from each of the
|
|
camera source pads. The camera source can simply get_caps on the peer of
|
|
each of its pads to know what are the allowed caps for that pad.
|
|
|