[virtio-dev] Re: [RFC PATCH v6] virtio-video: Add virtio video device specification

[Alexander Gordeev <alexander.gordeev@opensynergy.com>]

Hi Alexandre,

On 12.01.23 07:32, Alexandre Courbot wrote:
> Hi Alexander,
>
> On Thu, Jan 12, 2023 at 2:04 AM Alexander Gordeev
> <alexander.gordeev@opensynergy.com> wrote:
>>> +\subsubsection{Bitstream formats}\label{sec:Device Types / Video Device / Supported formats / Bitstream formats}
>>> +
>>> +The fourcc code of each supported bitstream format is given, as well as
>>> +the unit of data requested in each input resource for the decoder, or
>>> +produced in each output resource for the encoder.
>>> +
>>> +\begin{description}
>>> +\item[\field{MPG2}]
>>> +MPEG2 encoded stream. One Access Unit per resource.
>>> +\item[\field{H264}]
>>> +H.264 encoded stream. One NAL unit per resource.
>>> +\item[\field{HEVC}]
>>> +HEVC encoded stream. One NAL unit per resource.
>>> +\item[\field{VP80}]
>>> +VP8 encoded stream. One frame per resource.
>>> +\item[\field{VP90}]
>>> +VP9 encoded stream. One frame per resource.
>>> +\end{description}
>>> +
>> Actually I'm not sure where do these fourcc codes for bitstream formats
>> come from.
>>
>> In one of the old comments I found a reference to
>> https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2fwww.rfc%2deditor.org%2frfc%2frfc2361&umid=1c7e5b96-6438-489f-ae82-dfea03537169&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-9abf34a612eb36d608f592911fde3480af19c68e
>>
>> But it doesn't define MPG2, HEVC, VP80, VP90.
>>
>> Also there is this comment to virtio-video v1 from Tomasz Figa and the
>> related discussion:
>> https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2fmarkmail.org%2fmessage%2fgc6h25acct22niut%23query%3a%2bpage%3a1%2bmid%3aet4l3ni7qjqhiygo%2bstate%3aresults&umid=1c7e5b96-6438-489f-ae82-dfea03537169&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-d0ecfac6371fb65d9d93c694ba692ef42fe41d63
>>
>> He wrote that it is not worth it because there are so many conflicting
>> sets of fourcc codes.
>>
>> I can see that fourcc codes were not used in virtio-video spec draft
>> versions 1 to 5. So now it looks quite weird to see them here. Probably
>> this is because you'd like to mimic v4l2 interface more closely?
> These come from here:
> https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2fdocs.kernel.org%2fuserspace%2dapi%2fmedia%2fv4l%2fpixfmt%2dcompressed.html&umid=1c7e5b96-6438-489f-ae82-dfea03537169&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-4fbebb6ce3215a0e62782b61d287090a62d088dc
>
> V4L2 has a nice list of supported fourccs for coded formats, so I'd
> just suggest we refer to them and use them instead of defining our
> own.

Oops, somehow I overlooked that. Thanks!


--
Alexander Gordeev
Senior Software Engineer

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