> On May 17, 2025, at 01:10, Zhao Zhili <quinkblack-at-foxmail....@ffmpeg.org> > wrote: > > > >> On May 17, 2025, at 00:27, Timo Rothenpieler <t...@rothenpieler.org> wrote: >> >> On 16.05.2025 17:59, Zhao Zhili wrote: >>>> On May 16, 2025, at 22:52, Timo Rothenpieler <t...@rothenpieler.org> wrote: >>>> >>>> On 16/05/2025 16:24, Zhao Zhili wrote: >>>>> From: Zhao Zhili <zhiliz...@tencent.com <mailto:zhiliz...@tencent.com>> >>>>> ffmpeg -i input.mp4 -c copy -tag:v av01 output.flv >>>>> [flv @ 0x143204080] Tag av01 incompatible with output codec id '225' >>>>> (10va) >>>> >>>> I don't quite understand what causes this. >>>> Is this an issue when running on big endian architectures? >>>> I'm pretty sure I tested all combinations of codecs with muxing and >>>> demuxing, and never ran into that error. >>> The key point is when specify tag via command line, e.g., -tag:v av01, it’s >>> passed to AVCodecParameters codec_tag in little endian. >>> You didn’t see the error because without specify the tag explicitly, >>> codec_tag is copied >>> from AVOutputFormat codec_tag to AVCodecParameters codec_tag, so they are >>> the same. >>> Another example is codec_mp4_tags. >> >> This still irks me as wrong. >> There is _a lot_ of places all over flvenv.c, in all kinds of functions, >> that hard-depend on the values in par->codec_tag being from the _codec_ids >> tables at the top of the file. >> Like, they contain flv specific audio and video codec IDs for the >> pre-ext-flv codecs, those would all also break. >> >> So there seems to be a deeper issue there if those values can be overridden >> from the commandline. The encoder clearly does not expect that. >> >> Looking at the code this error comes from: >> https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/mux.c#L314 >> >> It looks to to me like it's working exactly as intended and required by >> flvenc, protecting it from invalid tags. >> >> So, when the user provides a custom tag that is invalid, isn't that kinda on >> the user? >> The check you're running into does what it's supposed to: >> It detects that the provided tag is invalid for this codec in this container. >> >> Why do you want to override it anyway? There is only exactly one valid tag >> for each codec. > > A user shows the error message to me. Because he know there are -tag option > for mp4, and > enhanced-rtmp use fourcc for extended codecs, so he thought it should work. > > The -tag:v av01 is redundant, it should be a NOP, not trigger error. The > strings “av01” > is the right order of fourcc in spec. The endian issue should be limited to > the internal. > Current error message is confusing, because it shows 10va instead of av01.
Doc from Microsoft shows fourcc use small endian https://learn.microsoft.com/en-us/windows/win32/directshow/fourcc-codes While wiki and enhanced rtmp spec says it’s big endian https://en.wikipedia.org/wiki/FourCC It’s clear in av_fourcc_make_string that we use small endian. For normal codec id in flv, e.g, 7 for H.264, it’s not a big issue, since they’re not fourcc. > >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
