[asterisk-dev] addons/format_mp3.c - why is OUTSCALE 4096?

Tony Mountifield tony at softins.co.uk
Fri Sep 23 09:16:02 CDT 2011

On some of my systems, we compress call recordings from wav to mp3
using sox/lame. I have been experimenting with playing back the mp3
files directly using the format_mp3 module.

I found that while playing back the wav file was at normal volume,
playing back the mp3 file was very quiet.

On investigation, I discovered that was because of the following line
in format_mp3.c:

#define OUTSCALE 4096

Now mpglib.h suggests the default value of outscale is 32768. If I change
the #define to 32768 instead and rebuild, mp3 files then play at the same
volume as other formats.

So my questions are: Why the setting of 4096? Can it be changed to make
format_mp3 consistent with all the other formats?


Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org

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