Testing Voice Recognition App ~ Audio Out to Mic In Adapter

Issue

I'm developing an Android voice recognition app for my master thesis. The app comes with different algorithms that transcribe voice.

To test which of them works best I want to feed the devices microphone with the same speech sample over and over again. I decided to use an open audio book from http://www.librivox.org.

I need an adapter to feed the audio book into my devices microphone input port since the Android VD (Emulator) does not support microphone input.

I have tested a direct connection:

AUDIO OUT (LAPTOP) ─────┐
                        ├─[SPLITTER]─────HEADSET PORT (Device)
                   ─────┘

* Splitter

This does sometimes work on my Sony Xperia ZL even though the quality is really bad. I also tried an iRig instead of the splitter - but I think the input for the iRig is only for guitars' line out.

So: Is there a way to feed some audio output to my Android devices microphone input?

Solution

Although I didn't manage to feed my real device's mic with audio from my laptop I found a solution.

THE DIGITAL WAY

Step 1: To test my app I now use an Android-x86 in a VirtualBox on Ubuntu. The Android-x86 is a Cyanogen modded Android 4.4 running on (virtual) machines and has microphone support (contrary to the original Android AVD). I tried this on Windows 8.1 but the mic stayed silent.

Step 2: I have to map my main audio output channel to a virtual audio input (virtual microphone). I mostly followed the instructions of this answer using PulseAudio, PulseAudio Volume Control and the magic command: sudo modprobe snd_aloop

Step 3: Set "Monitor of Built-In Analog Stereo" in PulseAudio Volume Control to standard device. Then set the Host Audio Driver to ALSA and run the machine.

THE ANALOG WAY

However I'm not giving up on the cable thing and will update this answer onSuccess().

Answered By - marfnk