firefoxwebrtcweb-audio-apiweb-mediarecordermediarecorder-api

Specifying codecs with MediaRecorder

How can I specify the codecs used with the MediaRecorder API? The only option I see is for mimeType which isn't really sufficient. Cramming in the codecs in the mimeType option doesn't seem to work.

var mediaRecorder = new MediaRecorder(
    outputMediaStream
  ),
  {
    mimeType: 'video/webm; codecs="opus,vp8"'
  }
);

This results in a WebM stream with Vorbis and VP8:

FFMPEG STDERR: Input #0, matroska,webm, from 'pipe:':
  Metadata:
    encoder         : QTmuxingAppLibWebM-0.0.1
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0(eng): Video: vp8, yuv420p, 640x360, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1(eng): Audio: vorbis, 44100 Hz, stereo, fltp (default)

If I make a MediaStream that only has an audio track (no video), then the MediaRecorder outputs Opus audio in an Ogg container:

FFMPEG STDERR: Input #0, ogg, from 'pipe:':
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Audio: opus, 48000 Hz, stereo, fltp
    Metadata:
      ENCODER         : Mozilla44.0.2

How can I get Opus audio with VP8 video in a WebM container with the MediaRecorder API?

Firefox v44.0.2

Solution

  • Check out the Chrome LayoutTests for isTypeSupported(), the mimeType used there should be applicable to the MediaRecorder constructor.