search

Vanilagy / webm-muxer

WebM multiplexer in pure TypeScript with support for WebCodecs API, video & audio.
https://vanilagy.github.io/webm-muxer/demo
MIT License
197 stars 12 forks source link

Audio as track 1? #10

Closed rafael2k closed 1 year ago

rafael2k commented 1 year ago

When encoding audio-only content, is the audio set to track 1? How to set to track 1?

Vanilagy commented 1 year ago

The audio is always set to track 2, currently. Is this an issue?

rafael2k commented 1 year ago

I'm seeing some warnings when decoding with ffmpeg's libavcodec, something like "track 1 not found" (and indeed, it does not exist, as only track 2 is present in an audio-only file).

rafael2k commented 1 year ago

The problem only occurs when I seek to some random file position. I get: [matroska,webm @ 0x7f30f0000bc0] Invalid track number 1

But indeed, the playback is perfect, without any issue.

Vanilagy commented 1 year ago

Mh, I see. I could make it so that audio gets track number 1 if there is no video track and you could check if it still errors. Thought the track numbers didn't matter and only uniqueness did. Let's hope it's not ffmpeg being confused by there being no video track

rafael2k commented 1 year ago

I can try it. Should I just hardcode AUDIOTRACK to 1 in the source and check if the warning still occurs?

Vanilagy commented 1 year ago

Yes do that

Vanilagy commented 1 year ago

Let me know if your change fixed your issue! If so, I'll write a proper fix for into the library itself and publish that.

rafael2k commented 1 year ago

So, setting AUDIO to track 1 and video to track 2, I get: [matroska,webm @ 0x7f45dc265180]Invalid track number 2

I think there is a need to also remove the reference for the video track in some header, right?

Vanilagy commented 1 year ago

How did you change the code? If I'm not mistaken, you'll simply need to swap the values of these two constants:

https://github.com/Vanilagy/webm-muxer/blob/fb38fc12bf3cbcf336189944e2ffb011b4cc2c39/build/webm-muxer.js#L432

And then simply don't specify a video track for the muxer and none should be included.

rafael2k commented 1 year ago

I just swapped the track numbers, indeed, as you mention. But now track 2 shows up as invalid in the warning by ffmpeg matroska/webm demuxer (and I did not specified no video track to the muxer).

rafael2k commented 1 year ago

This is what mkvinfo shows. I think there should be an issue with ffmpeg demuxer, not really with webm-muxer... [EDIT: please read the following comment - I found the issue!]

rafael2k commented 1 year ago

Found the issue. It is related to the cues. Eg (audio is track 1, there is no video): |+ Cues | + Cue point | + Cue time: 00:00:00.000000000 | + Cue track positions | + Cue track: 2 | + Cue cluster position: 4325 | + Cue point | + Cue time: 00:00:01.000000000 | + Cue track positions | + Cue track: 2 | + Cue cluster position: 12837 | + Cue point | + Cue time: 00:00:02.000000000 | + Cue track positions | + Cue track: 2 | + Cue cluster position: 21350

rafael2k commented 1 year ago

Using stock webm-muxer, without change, when creating an audio-only file (where audio track is nr. 2), I get: |+ Cues | + Cue point | + Cue time: 00:00:00.000000000 | + Cue track positions | + Cue track: 1 | + Cue cluster position: 4325 | + Cue point | + Cue time: 00:00:01.000000000 | + Cue track positions | + Cue track: 1 | + Cue cluster position: 12837 | + Cue point | + Cue time: 00:00:02.000000000 | + Cue track positions | + Cue track: 1 | + Cue cluster position: 21350 | + Cue point | + Cue time: 00:00:03.000000000 | + Cue track positions | + Cue track: 1 | + Cue cluster position: 29863 | + Cue point | + Cue time: 00:00:04.000000000 | + Cue track positions | + Cue track: 1 | + Cue cluster position: 38536

Vanilagy commented 1 year ago

Ah, I see what the bug is now! I had hardcoded the cues to always point to the video track, disregarding the fact that it might not be there. I just published a new version that should fix this issue. Could you try it out?

rafael2k commented 1 year ago

Yes, will try it now, tks!

rafael2k commented 1 year ago

Cues are appearing in track 2 now! Seems all good now, and libavcodec matroska demuxer does not complain anymore. Yay!

Vanilagy commented 1 year ago

Awesome! Thanks for cooperating.

rafael2k commented 1 year ago

Thank you for the awesome muxer!