linux-kernel - Re: [PATCH v7 5/9] media: venus: vdec: add video decoder files

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Message-ID: <1490626683.5935.18.camel@ndufresne.ca>
Date:   Mon, 27 Mar 2017 10:58:03 -0400
From:   Nicolas Dufresne <nicolas@...fresne.ca>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v7 5/9] media: venus: vdec: add video decoder files

Le lundi 27 mars 2017 à 10:45 +0200, Hans Verkuil a écrit :
> > > timestamp and sequence are only set for CAPTURE, not OUTPUT. Is
> > > that correct?
> > 
> > Correct. I can add sequence for the OUTPUT queue too, but I have no
> > idea how that sequence is used by userspace.
> 
> You set V4L2_BUF_FLAG_TIMESTAMP_COPY, so you have to copy the
> timestamp from the output buffer
> to the capture buffer, if that makes sense for this codec. If not,
> then you shouldn't use that
> V4L2_BUF_FLAG and just generate new timestamps whenever a capture
> buffer is ready.
> 
> For sequence numbering just give the output queue its own sequence
> counter.

Btw, GStreamer and Chromium only supports TIMESTAMP_COPY, and will most
likely leak frames if you craft timestamp.

Nicolas
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