> 在 2025年5月17日，上午1:39，Timo Rothenpieler <t...@rothenpieler.org> 写道： > > On 16.05.2025 19:24, Zhao Zhili wrote: >>>> 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. > > This patch just fixes it for a very small subset of codecs in flv though. > There's nothing indicating that -tag:v is needed or sensibly supported in > flvenc. > If you'd want to pass h264 or aac as fourcc, it'd be flat out impossible, and > no easy fix is available. > > I'd rather not complicate flvenc, even if just a little bit, just to swap > around the endianness of the few codecs that do use a fourcc based tag. > > flvenv should probably just completely ignore -tag:v, since the option makes > no sense for it anyway.
I can remove setting tag list to AVOutputFormat, does that works for you? > And maybe print a warning when it's used only. > _______________________________________________ > 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".
