[ecasound] How to find out if an mp3/ogg file is mono or stereo?

Dear list.

I'm using the Ecasound interactive mode via the C++ interface
(eca-control-interface.h) in an application to play audio files via
JACK.
Therefore, I first load the files into a dummy chain-setup to get the
number of channels and then create another chain-setup with the
correct number of channels (using cs-set-audio-format).

This works well for WAV and FLAC files, but I cannot manage to get the
correct number of channels for mono MP3 and OGG files.

This is how to reproduce my problem:

ecasound -c

> ai-add house_lo.mp3
> ao-add null
> cs-connect
> ai-index-select 1
> ai-get-format

This produces "s16_le,2,11025", although the file is actually mono.

I got the file from there:
https://bitbucket.org/pygame/pygame/src/default/examples/data/house_lo.mp3

I tried with several different MP3-files and none of them was
correctly recognized as mono file.

It doesn't seem to work with OGG-files either, I tried this for example:
https://bitbucket.org/pygame/pygame/src/default/examples/data/house_lo.ogg

How can I find out the correct number of channels?

Or is there another way to create a chain-setup for playback with JACK
which automatically uses the correct number of channels (instead of
the default 2)?

cheers,
Matthias

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Received on Wed May 29 12:15:03 2013