Android: Record and Playback audio from different devices

Question

I'm trying to record and play audio using different devices with AudioRecord and AudioTrack and setting preferredDevice to set the devices to each.

    audioRecord = AudioRecord(
                            MediaRecorder.AudioSource.VOICE_COMMUNICATION,
                            sampleRate,
                            AudioFormat.CHANNEL_IN_MONO,
                            AudioFormat.ENCODING_PCM_FLOAT,
                            frameSize * Float.SIZE_BYTES
                        )
    audioRecord?.preferredDevice = mic

    audioTrack = AudioTrack.Builder()
                    .setAudioAttributes(
                        AudioAttributes.Builder()
                            .setUsage(AudioAttributes.USAGE_VOICE_COMMUNICATION)
                            .setContentType(AudioAttributes.CONTENT_TYPE_SPEECH)
                            .build()
                    )
                    .setAudioFormat(
                        AudioFormat.Builder()
                            .setEncoding(AudioFormat.ENCODING_PCM_FLOAT)
                            .setSampleRate(PLAYBACK_SAMPLE_RATE)
                            .setChannelMask(AudioFormat.CHANNEL_OUT_MONO)
                            .build()
                    )
                    .setBufferSizeInBytes(frameSize * Float.SIZE_BYTES * 2)
                    .build()

    audioTrack?.preferredDevice = speaker

It works fine when both input and out are preferred to one device, but when selecting different devices, the mic(AudioRecord) is also using the speaker's preferred device. Even when I log the audioRecord?.routedDevice, it doesn't seem to change to the preferred device for AudioRecord but uses the same preferred AudioTrack.

Note: I'm trying to switch between a Wired headset, a Bluetooth device and the Android device's default audio hardware.

Any idea what could be the issue here? Or is it not possible to use two devices for input and output like in iOS?

Answer 1

You need to check if setPreferredDevice returns true.

It returns false if the specified AudioDeviceInfo is non-null and does not correspond to a valid audio input/output device.

I assumed mic and speaker is not null because if deviceInfo is null, default routing is restored.