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edimuj / cordova-plugin-audioinput

This iOS/Android Cordova/PhoneGap plugin enables audio capture from the device microphone, by in near real-time forwarding audio to the web layer of your application. A typical usage scenario for this plugin would be to use the captured audio as source for a web audio node chain, where it then can be analyzed, manipulated and/or played.
https://github.com/edimuj/app-audioinput-demo
MIT License
161 stars 88 forks source link

audioinput event seems to ignore sample rate #81

Closed smgdesign closed 5 years ago

smgdesign commented 5 years ago

Hi there, great plugin, it's really useful!

I'm using it in Cordova and recording wav input from the microphone into an array buffer that I then pass to a C library for audio analysis.

It's all working really well, but the audioinput event doesn't seem to be listening to the sample rate I set. I'm probably using it wrong, or misunderstanding the way the event is utilised but was wondering if you could identify if there's an issue?

This is my captureCfg: sampleRate: window.audioinput.SAMPLERATE.VOIP_16000Hz, bufferSize: 8192, channels: window.audioinput.CHANNELS.MONO, format: window.audioinput.FORMAT.PCM_16BIT, normalize: false, audioSourceType: window.audioinput.AUDIOSOURCE_TYPE.DEFAULT

And I have confirmed when I run window.audioinput.getCfg() that the sample rate is being used by the plugin. But the capture event is running containing 8192 samples far more frequently than I am expecting with 16kHz.

Initiating the audioinput event with window.addEventListener('audioinput', this.onAudioInputCapture, false) and I simply concatenate the evt.data to an object each time.

I hope this is enough information to help highlight where I'm going wrong with it!

edimuj commented 5 years ago

Thanks! Well, depending on which device you run your app on, not all samplerates are supported. I believe that on iOS for example, the minimum samplerate is 22050Hz. Could that explain your issue?

smgdesign commented 5 years ago

Hi, thanks for the reply. I did some more investigation and can confirm that the minimum sample rate for iOS is actually 8kHz so that definitely wasn't the issue. I forked the plugin and set it up locally to do some debugging and found that the sample rate was being followed by the capture event. I had an issue converting the data, once I corrected that problem, the number of samples reflected what I was expecting. Many thanks for getting back to me.

edimuj commented 5 years ago

Good to hear that you solved this, and thanks for the update.