Gstreamer V4l2 Codec elements for video encoders/decoders.

[Nicolas Dufresne]

Le mardi 09 avril 2019 à 01:30 -0500, Amit Pandya a écrit :
> Hi Nicolas,
> 
> Do DRC (Dynamic Resolution Change) verified to be supported using gst-v4l2
> decoder plugins on any of the supported platforms?

Never seen such an acronyme, makes things looks less organic. Yes,
resolution changes work on some platform (notably IMX.6 CODA), but very
few of them. The implementation is not optimal, it consist of a full
decoder reset. With the new specification being worked on, and the
validation test that will come with it, we should start having proper
support for the new, and more optimal mechanism (SOURCE_CHANGE events).
There is patches attached on an issue (yes some people don't yet
understand merge request) that implements SOURCE_CHANGE event handling,
and the implementation seems to be in the right direction.

https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/issues/587

> 
> If the input stream contains two concatenated SPS/PPS sequence, does the
> gst-v4l2 decoder handle newstreamformat event by doing all the
> STREAM-OFF/REQBUF(0)/G_FMT/REQBUF(x)/STREAM-ON sequence ? 

You'll need h264parse in front of your decoder for the current
implementation to work with pre-announced SPS/PPS. The h264parse
element should detect SPS/PPS activation and update the caps
accordingly. The SOURCE_CHANGE event would not depend on this directly,
since it's the decoder that triggers this event on SPS/PPS activation,
and it will only do that is needed. Note that none of the driver have
implemented support for reusing larger buffers for smaller resolution
yet, but it's a well known technique that will likely happen in the
future (or could be contributed of course).

All this is in the expert hands of the kernel maintainers.

> 
> -Regards
> Amit Pandya
> 
> 
> 
> --
> Sent from: http://gstreamer-devel.966125.n4.nabble.com/
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