What is correct parameters for opus webm audio to seekable with ffmpeg?

Question

I tried to record audio.webm using HTML5 MediaRecorder on Chrome and it cannot seek. Which is a known bug for Chrome. And I'm using ffmpeg to fix this problem with billion different ways, but still haven't succeeded.

ffmpeg -i <source> -fflags +genpts output.webm

It works if the source file has a video stream, but it didn't work for only audio stream with opus encoding. When I try to seek, Chrome dev tools network timeline keep downloading the entire file:

I even tried to play with VLC and still cannot seek. Then I tried to convert webm to MP3:

ffmpeg -i <source> output.mp3

Now I can seek in the browser and any other media players, but the output file's duration and start time is incorrect:

What is the correct ffmpeg parameters to fix this problem?

If we know what the Chrome bug is, that may give a clue as to how to work around it. — Gyan, Nov 11 '19 at 05:12
I'm not sure about it, but I think framedata or metadata is missing or malformed on Chrome MediaRecorder. — jeefo, Nov 11 '19 at 05:31
This is the [Chrome bug](https://bugs.chromium.org/p/chromium/issues/detail?id=642012) link marked WontFix. — jeefo, Nov 11 '19 at 06:14
Try `ffmpeg -i -c copy output.webm` and `ffmpeg -fflags +genpts -i -c copy output.webm` — Gyan, Nov 11 '19 at 06:54

score 3 · Accepted Answer · answered Nov 12 '19 at 19:13

3

I've been research about it and found an issue discussion from https://github.com/GoogleChromeLabs. In the issue discussion they used a node module called ts-ebml. It's like:

ts-ebml -s not_seekable.webm | cat > seekable.webm

It fixed non-seekable webm metadata duration and cues.

I hope it will be help somebody.

answered Nov 12 '19 at 19:13

jeefo

71
8

Which issue discussion you are referring to? Where do you get `ts-ebml`? – jarno Oct 03 '20 at 20:45
Sorry, I don't remember and cannot find it now. It was a year ago. – jeefo Oct 07 '20 at 00:17
1

I just found a reference https://github.com/GoogleChromeLabs/webm-wasm/issues/3 – jeefo Oct 07 '20 at 00:20
You can get it via npm: `npm i -g ts-ebml` – starikcetin Aug 15 '23 at 16:42

What is correct parameters for opus webm audio to seekable with ffmpeg?

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