linux-kernel - Re: [PATCH v2 3/3] media: docs: dev-stateless-decoder: Document frame type flags

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Message-ID: <ceedff4c-3233-23c7-41f0-183fa8d75c9a@gmail.com>
Date:   Wed, 26 Jan 2022 15:33:03 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Nicolas Dufresne <nicolas@...fresne.ca>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:     linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        kernel <kernel@...labora.com>
Subject: Re: [PATCH v2 3/3] media: docs: dev-stateless-decoder: Document frame
 type flags

25.01.2022 23:37, Nicolas Dufresne пишет:
> Le dimanche 16 janvier 2022 à 21:55 +0300, Dmitry Osipenko a écrit :
>> Document that frame type flags must be set for the coded buffer.
>> Decoders, like NVIDIA Tegra h264 decoder for example, won't work
>> properly without these flags.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  .../userspace-api/media/v4l/dev-stateless-decoder.rst          | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst b/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
>> index 4a26646eeec5..845f4481d34f 100644
>> --- a/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
>> +++ b/Documentation/userspace-api/media/v4l/dev-stateless-decoder.rst
>> @@ -271,6 +271,9 @@ A typical frame would thus be decoded using the following sequence:
>>            we are not sure that the current decode request is the last one needed
>>            to produce a fully decoded frame, then
>>            ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` must also be set.
>> +          ``V4L2_BUF_FLAG_KEYFRAME``, ``V4L2_BUF_FLAG_PFRAME`` and
>> +          ``V4L2_BUF_FLAG_BFRAME`` must be set if relevant to the coded
>> +          format.
> 
> I think I would rather keep this in the CODEC specific APIs (BFrame being an
> MPEG specific concept). If I knew about this before we made the API final, I
> would have added the slice_type bitstream parameter in the
> v4l2_h264_decode_params structure. But as the types are rather limited, I would
> preserve our "reservered" space and make that part of the
> V4L2_H264_DECODE_PARAM_FLAGS_{} instead. Do you also need that for HEVC ? (do
> you have HEVC on that generation of tegra ?)

That generation of Tegra doesn't support HEVC. I'll try to move frame
type to v4l2_h264_decode_params, thank you.