what is the best audiosource setting for calls?

Question

I am using the following code in my messenger calling app :

this.audioRecord = new AudioRecord(
                MediaRecorder.AudioSource.DEFAULT,
                Constants.SAMPLE_RATE,
                AudioFormat.CHANNEL_IN_MONO,
                AudioFormat.ENCODING_PCM_16BIT,
                Constants.BUFFER_SIZE_RECORDING);

Is this the best setting for audio in calls? I have a couple of issues with echos. I tried AudioSource.MIC and VOICE_COMMUNICATION, but they perform worse. I wonder if changing any of the other variables would improve the audio quality? Any ideas about the best variable for a calling app.Also, I don't hear any audio often on Nexus 6 or pixel 2

Answer 1

Audio on Android is always a tough problem because manufacturers put in different audio chips with different capabilities in all phones.

That being said VOICE_COMMUNICATION should be your best bet. It is "Microphone audio source tuned for voice communications such as VoIP. It will, for instance, take advantage of echo cancellation or automatic gain control if available."

So it should already use AcousticEchoCanceler and NoiseSuppressor to get rid of echoes and other disturbing noises. But in the end, it comes down to your use-case, if you rather want unfiltered or filtered audio.

You can also try to increase the sampling rate (Constants.SAMPLE_RATE 48000 should be best since that is the sampling rate of most modern phones) and bit depth (ENCODING_PCM_16BIT to ENCODING_PCM_FLOAT) to get a better signal. Note that supported sampling rates differ from phone to phone. To find out what your phone supports adapt the solution from audio sampling rates discussion. More information about sampling rates is covered in the Sampling Audio docs.

To the problem that you often don't hear anything, that can happen if either your gain is too low (can happen with AudioSource.MIC) or if your recorder is not ready yet (I'm making an educated guess here since I don't know your code).