Hi Alexandre,
On 12.01.23 07:32, Alexandre Courbot wrote:
Hi Alexander,
On Thu, Jan 12, 2023 at 2:04 AM Alexander Gordeev
<[email protected]> 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
OpenSynergy GmbH
Rotherstr. 20, 10245 Berlin
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