CODEWITHSUNDEEP
web-audio-api
Charles Horowitz
Charles Horowitz

Reputation: 31

Zero-value data in createmediastreamsource input buffer when recording using web-audio

I am attempting to record live audio via USB microphone to be converted to WAV and uploaded to a server. I am using Chrome Canary (latest build) on Windows XP. I have based my development on the example at http://webaudiodemos.appspot.com/AudioRecorder/index.html

I see that when I activate the recording, the onaudioprocess event input buffers (e.inputBuffer.getChannelData(0) for example) are all zero-value data. Naturally, there is no sound output or recorded when this is the case. I have verified the rest of the code by replacing the input buffer data with data that produces a tone which shows up in the output WAV file. When I use approaches other than createMediaStreamSource, things are working correctly. For example, I can use createObjectURL and set an src to that and successfully hear my live audio played back in real time. I can also load an audio file and using createBufferSource, see that during playback (which I hear), the inputBuffer has non-zero data in it, of course.

Since most of the web-audio recording demos I have seen on the web rely upon createMediaStreamSource, I am guessing this has been inadvertantly broken in some subsequent release of Chrome. Can anyone confirm this or suggest how to overcome this problem?

Upvotes: 3

Views: 1035

Answers (1)

cwilso
cwilso

Reputation: 13928

It's probably not the version of Chrome. Live input still has some high requirements right now:

1) Input and output sample rates need to be the same on Windows 2) Windows 7+ only - I don't believe it will work on Windows XP, which is likely what is breaking you. 3) Input device must be stereo (or >2 channels) - many, if not most, USB microphones show up as a mono device, and Web Audio isn't working with them yet.

I'm presuming, of course, that my AudioRecorder demo isn't working for you either.

These limitations will be removed over time.

Upvotes: 2

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