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Subject: Re: [PATCH 10/10] venus: dec: make decoder compliant with stateful
 codec API
From:   Nicolas Dufresne <nicolas@ndufresne.ca>
To:     Tomasz Figa <tfiga@chromium.org>
Cc:     Stanimir Varbanov <stanimir.varbanov@linaro.org>,
        Linux Media Mailing List <linux-media@vger.kernel.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Vikash Garodia <vgarodia@codeaurora.org>,
        Alexandre Courbot <acourbot@chromium.org>,
        Malathi Gottam <mgottam@codeaurora.org>,
        Philipp Zabel <p.zabel@pengutronix.de>
Date:   Wed, 30 Jan 2019 10:32:28 -0500
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Le mercredi 30 janvier 2019 à 15:17 +0900, Tomasz Figa a écrit :
> > I don't remember saying that, maybe I meant to say there might be a
> > workaround ?
> > 
> > For the fact, here we queue the headers (or first frame):
> > 
> > https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/blob/master/sys/v4l2/gstv4l2videodec.c#L624
> > 
> > Then few line below this helper does G_FMT internally:
> > 
> > https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/blob/master/sys/v4l2/gstv4l2videodec.c#L634
> > https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/blob/master/sys/v4l2/gstv4l2object.c#L3907
> > 
> > And just plainly fails if G_FMT returns an error of any type. This was
> > how Kamil designed it initially for MFC driver. There was no other
> > alternative back then (no EAGAIN yet either).
> 
> Hmm, was that ffmpeg then?
> 
> So would it just set the OUTPUT width and height to 0? Does it mean
> that gstreamer doesn't work with coda and mtk-vcodec, which don't have
> such wait in their g_fmt implementations?

I don't know for MTK, I don't have the hardware and didn't integrate
their vendor pixel format. For the CODA, I know it works, if there is
no wait in the G_FMT, then I suppose we are being really lucky with the
timing (it would be that the drivers process the SPS/PPS synchronously,
and a simple lock in the G_FMT call is enough to wait). Adding Philipp
in CC, he could explain how this works, I know they use GStreamer in
production, and he would have fixed GStreamer already if that was
causing important issue.

Nicolas