On 12/28/25 19:45, Jun Zhao via ffmpeg-devel wrote:
PR #21307 opened by Jun Zhao (mypopydev)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21307
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21307.patch
Add functions to parse AV1 OBUs in MPEG-TS start code format
(0x000001 prefix). This is needed for AV1 streams from MPEG-TS
containers per AOM AV1 in MPEG-2 TS specification.
I have some questions around aligned PES and start codes; please correct
me if I am wrong.
Start codes: it seems to me current PR autodetects start codes, which
means if a stream miss them, it would still be successfully decoded.
This is possible because, additionally, AV1 requires aligned PES (which
is unusual for h2645 typically). Being able to handle non-conformant
files is nice until there are no downsides. The situation is maybe a
little bit tricky here since this format is not widespread, you may want
to be more carefull, check interoperability etc., and maybe you want to
be warned that "this file may not be supported outside of ffmpeg" ? It
seems there is no "issue" in the other way (a stream which is not
pes-aligned would not be decodable since there is no "find_frame_end" in
the parser to split the packets), but anyway maybe it could be
an interesting opportunity to introduce pes alignment support in mpegts
? If I understand correctly, it would allow disabling packet repacking
in some use cases (j2k for example: I just had a quick look today since
mpegts mandates pes alignment for it too).
Nicolas
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