Does WebM support PCM for the audio codec?
I didn't think it did, but I see on the WebM documentation page that there is support for a BitDepth field with the following comment:
BitDepth - Bits per sample, mostly used for PCM.
If WebM does support PCM, does Chrome's implementation? And if it does, what is the appropriate content type for use with MediaRecorder? These all return false:
MediaRecorder.isTypeSupported('video/webm;codecs=h264,pcm');
MediaRecorder.isTypeSupported('video/webm;codecs=h264,wav');
MediaRecorder.isTypeSupported('video/webm;codecs=h264,adpcm');
MediaRecorder.isTypeSupported('video/webm;codecs=h264,pcm_s16le');
MediaRecorder.isTypeSupported('audio/wav');
PCM is now supported in the latest Chromium. Here is a reference for the list of valid mime types for MediaRecorder in Chromium.
As a snapshot, here is the ones currently supported in Google Chrome Version 64.0.3282.167 (Official Build) (64-bit):
MediaRecorder.isTypeSupported("video/webm")
MediaRecorder.isTypeSupported("video/webm;codecs=vp8")
MediaRecorder.isTypeSupported("video/webm;codecs=vp9")
MediaRecorder.isTypeSupported("video/webm;codecs=vp8.0")
MediaRecorder.isTypeSupported("video/webm;codecs=vp9.0")
MediaRecorder.isTypeSupported("video/webm;codecs=h264")
MediaRecorder.isTypeSupported("video/webm;codecs=H264")
MediaRecorder.isTypeSupported("video/webm;codecs=avc1")
MediaRecorder.isTypeSupported("video/webm;codecs=vp8,opus")
MediaRecorder.isTypeSupported("video/webm;codecs=vp8,pcm")
MediaRecorder.isTypeSupported("video/WEBM;codecs=VP8,OPUS")
MediaRecorder.isTypeSupported("video/webm;codecs=vp9,opus")
MediaRecorder.isTypeSupported("video/webm;codecs=vp9,pcm")
MediaRecorder.isTypeSupported("video/webm;codecs=vp8,vp9,opus")
MediaRecorder.isTypeSupported("video/webm;codecs=h264,opus")
MediaRecorder.isTypeSupported("video/webm;codecs=h264,vp9,opus")
MediaRecorder.isTypeSupported("video/x-matroska;codecs=avc1")
MediaRecorder.isTypeSupported("audio/webm")
MediaRecorder.isTypeSupported("audio/webm;codecs=opus")
MediaRecorder.isTypeSupported("audio/webm;codecs=pcm")
Note that if you are running Chromium, you need to have it built with proprietary_codecs support for some of the more exotic ones with h264/avc1 to work.