This is a rather old question, but just came across it and thought that I would at least offer a solution for all future visitors who stumble on this issue:
The MediaStreamRecorder API is not currently implemented in chrome , however, some users have found alternative ways to make it work by stitching .webp images in a .webm video. Now, it may not be the best idea to use this experiment, but other projects have significantly advanced this idea by introducing a cross-platform library that implements this idea (and another specific browser solution), of which the first is definitely called MediaStreamRecorder . Another option of RecordRTC that I used in the past, one of the advantages of which is that they have specific Ruby server-side code to make it work neatly (not what you need if you want to do a simple download, but sometimes you may need to do more).
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