CODECS for HLS mux hard coded to 4

[David Johansen]

Summary of the bug:
How to reproduce:

ffmpeg -i test.mp4 -c:v copy -c:a copy -map v:0 -map a:0 -tag:v hvc1 -master_pl_name index.m3u8 -f hls "%v/index.m3u8"
6.1.1
Built on macOS with homebrew

The tier is hard coded to 4 and I'd be glad to submit a patch to fix this, but need some guidance on where the value should be pulled from:
​https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/e38092ef9395d7049f871ef4d5411eb410e283e0:/libavformat/hlsenc.c#l413

[David Johansen]

The problem is actually the B01 on the end of CODECS and I'm guessing that needs to be made dynamic instead of being hard coded

Here's the issues it's causing with playback in Chrome:
​https://github.com/videojs/video.js/issues/8549
​https://github.com/video-dev/hls.js/issues/6086

[David Johansen]

It appears that the logic is in section 5.2.1 of this document:
​https://www.etsi.org/deliver/etsi_ts/103200_103299/103285/01.01.01_60/ts_103285v010101p.pdf

[Jack Lau]

Is this still a problem?
I test it on newer chrome and didn't meet this error.

[Balling]

I test it on newer chrome and didn't meet this error.

It is not an issue in Chrome, but in Video.js javascript library...

" ffmpeg has part of CODECS hard coded to 4 and B01 on the end. "

Was that fixed?

[Jack Lau]

Replying to Balling:

I test it on newer chrome and didn't meet this error.

It is not an issue in Chrome, but in Video.js javascript library...

" ffmpeg has part of CODECS hard coded to 4 and B01 on the end. "

Was that fixed?

https://ffmpeg.org/pipermail/ffmpeg-devel/2025-March/340524.html
or
​https://patchwork.ffmpeg.org/project/ffmpeg/patch/tencent_886E16976F6A0C014A440BEF65EEA4694405@qq.com/
Please check if this patch is useful?

[Jack Lau]

I tested many cases, and found the reason of this bug.

Refer to ISO/IEC14496-15, CONSTRAINTS(like b0.1 or 90.0) is a hexadecimal representation of the general_constraint_indicator_flags. And each byte is separated by a '.', and trailing zero bytes may be omitted. (I write this descriptions in my patch)

So the hard code(B01) is not the only problem, the main problem is that "B01" does not conform to the correct syntax, the correct syntax should be "B0.1"

Of course, i test that video with coded "b0.1", it can played well in hls.js.

you can test the video (coded "b0.1")"​https://raw.githubusercontent.com/JackLau1222/hls_test/refs/heads/main/master_videotoolbox_test.m3u8" using hls.js, and you'll see it works well

I tested this patch on my computer and it worked fine, so please let me know if this patch solves your problem or if there is something else wrong
thx

[Balling]

"So the hard code(B01) is not the only problem, the main problem is that "B01" does not conform to the correct syntax, the correct syntax should be "B0.1""

Wow, you are right.

[Balling]

Would be nice to fix #10775 and #11316 while at it.

[Steven Liu]

Great job,
Thanks Jack Lau

fix by commit: 1502551dd363b3651a0e41f981f47657a8d29f82