I have mp3s of radio talk shows in which the host interviews people on the phone. The host uses a microphone, and the interviewee uses either a landline phone or a cell phone.
I want to save just the telephone audio to a different file. Is that feasible?
There might be much discrepency in the signal's characteristics of the interviewee that depends partialy on the phones they're using, their mobile operator, etc...
It is much easier to extract the radio's speaker signal. Then, everything that does not come form the radio's host must be from one of the interviewees.
What you need to do is to analyse the signal of the radio's speaker that might contains more prominent low-pitched components for example (depends obviously on the station you recorded from). Also use a window of analysis sufficiently large to take into account that every stream must last at least 500/1000ms. That might introduce a little stability in your extraction.
If you want to split the different interviewees, you can pose the simple condition that interviewee/host must alternate.
Here is a way to do this:
First analyze the audio, hone in on the frequencies that are prelevant in one of the signals, but not the other. Use a steep FIR filter to isolate roughly those frequencies. Also, you might want to use some averaging (moving average) to even out the signal.
Next, use a side chained gate triggered by the filtered audio. The gate should remove the silent parts. If it turns out that the silent parts are what you want, simply combine the audio stream with polarity inverted original.
