[FFmpeg-user] Firefox supports MP4 FLAC

[zeromux at tuta.io]

Hello, FFmpeg talk!

Starting from Firefox 51, you can play FLAC files directly in Firefox. According to their wiki, Firefox 51 also supports "MP4 FLAC"

https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats
> Starting in Firefox 51, you can play MP4 files using the FLAC codec, both with and without MediaSource Extensions and DRM support.

... MediaSource.isTypeSupported('audio/mp4; codecs="flac"')
... true

but I can't really put an FLAC file into an MP4 container.

$ ffmpeg -i a.flac -acodec copy -vn b.mp4
Stream #0:0: Audio: flac, 44100 Hz, stereo (16 bit)
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument

Any ideas how to make an "MP4 FLAC" file?