Re: coda: not generating EOS event

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Pawel,

On 12/11/14 15:42, Nicolas Dufresne wrote:
> Le jeudi 11 décembre 2014 à 11:00 -0200, Fabio Estevam a écrit :
>> Hi,
>>
>> I am running Gstreamer 1.4.4 with on a imx6q-sabresd board and I am
>> able to decode a video through the coda driver.
>>
>> The pipeline I use is:
>> gst-launch-1.0 filesrc
>> location=/home/H264_test1_Talkinghead_mp4_480x360.mp4 ! qtdemux !
>> h264parse ! v4l2video1dec ! videoconvert ! fbdevsink
> 
> This is a known issue. The handling of EOS and draining is ill defined
> in V4L2 specification. We should be clarifying this soon. Currently
> GStreamer implements what was originally done in Exynos MFC driver. This
> consist of sending empty buffer to the V4L2 Output (the input), until we
> get an empty buffer (bytesused = 0) on the V4L2 Capture (output).
> 
> The CODA driver uses the new method to initiate the drain, which is to
> send V4L2_DEC_CMD_STOP, this was not implemented by any driver when GST
> v4l2 support was added. This is the right thing to do. This is tracked
> at (contribution welcome of course):
> 
> https://bugzilla.gnome.org/show_bug.cgi?id=733864
> 
> Finally, CODA indicate that all buffer has been sent through an event,
> V4L2_EVENT_EOS. This event was designed for another use case, it should
> in fact be sent when the decoder is done with the encoded buffers,
> rather then when the last decoded buffer has been queued. When correctly
> implemented, this event cannot be used to figure-out when the last
> decoded buffer has been dequeued.
> 
> During last workshop, it has been proposed to introduce a flag on the
> last decoded buffer, _LAST. This flag could also be put on an empty

Are you planning to work on this? That was my assumption, but it's probably
a good idea to check in case we are waiting for one another :-)

Regards,

	Hans

> buffer to accommodate driver like MFC that only know it's EOS after the
> last buffer has been delivered. This all need to be SPECed and
> implemented. If you need to get that to run now, the easiest might be to
> hack CODA to mimic MFC behavior. Implement DEC_CMD_STOP in GStreamer
> shall not be very hard though, it simply need someone to do it.
> 
> cheers,
> Nicolas
> 
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