Clarification on how AP.exe handles mono vs stereo audio when --channels is not specified

[mtshiao]

Hi,

I’m currently using AP.exe (audio2csv) to analyze a large number of WAV files recorded at 44.1 kHz using autonomous recorders. These recordings are in stereo format. I have a question regarding how AP.exe handles multi-channel input, particularly stereo files, when the --channels option is not specified.

My questions are:
What is the default behavior of audio2csv when processing stereo WAV files (2 channels) without the --channels argument?
Does it process only the first channel (channel 0 / left)? Or does it mix both channels? If the input is mono, I assume that is handled normally—can you confirm?

I’ve reviewed the 2018 workshop materials. I did find this snippet in the CLI help: "The default value is nothing (not specified) which means that all channels are used. Channels are numbered 0, 1, 2, … In the usual case of stereo, left = 0 and right = 1."
But from what I’ve seen and what others in the community have noted, AP.exe may only process channel 0 by default, even if stereo input is provided and --channels is omitted. Is this true?

Thank you
Looking forward to any clarification or best-practice suggestions.

Best regards,
Ming-Tang Shiao

[atruskie]

The default behaviour is to mix the channels together. For recorders where the two microphones are very close, this is usually a good choice. But if you have your microphones very far apart, you'll want to analyse the channels individually.

The default is here:

audio-analysis/src/AnalysisPrograms/AnalyseLongRecordings/AnalyseLongRecordings.Arguments.cs

Line 79 in 23a0bbf

public bool MixDownToMono { get; set; } = true;

[mtshiao]

It’s great to know that the default behavior mixes the channels, and that we can control it via --mixDownToMono.
This helps a lot in deciding how to handle recordings with different mic configurations.

Really appreciate your support!