gst/camerabin2/camerabin2-src.txt - imx-gst-plugins-bad - Git at Google

 === 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 overriden 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.
	=== 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 overriden 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.