Re: Recording Stereo Mix and Microphone at the same time

["Måns Rullgård" <mans@mansr.com>]

Doug Lee <dgl@dlee.org> writes:

> On Mon, Apr 24, 2017 at 02:15:55PM +0200, Dino Vidakovic wrote:
>>    I'm trying to record both sources at the same time into a single file.
>>    Is this possible with Sox? If not, does anyone have any ideas or best
>>    practices to achieve this?
>
> If you just mean two devices into one file, I would think something
> like this would work, where your device names may vary:
>
> sox -m -t waveaudio "Microphone (Logitech Wireless H" -t waveaudio "Microphone (Andrea PureAudio US" outfile.wav
>
> Timings may vary slightly among devices though; so if you're trying to
> get real-time, more-than-two-channel data mixed down to two channels,
> your results may and may not be pleasing.

There are two time-related issues with this.  Firstly, the two devices
may not start recording at exactly the same time.  The tracks will then
have to be realigned after recording, which is easy enough if they all
start with an externally generated sync signal.  Secondly, the ADC
clocks of the devices can (will) drift relative to each other eventually
leading to a buffer overflow or underflow since Sox assumes all inputs
have synchronised samples.  There is no easy fix for this.

-- 
Måns Rullgård

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