Re: [mpg123-users] how to control the pitch remotely

[Thomas O. <tho...@or...>]

Am Tue, 29 Jun 2010 18:11:32 +0100
schrieb zonyi besk <zo...@gm...>: 

> > Tried with raw output but still not changed the pitch.

> > pv -L 30000 foo.mp3 | mpg123 -q -R --fifo /dev/shm/mpg123-cmd1 --remote-err
> > -s - | lame -x - > out.mp3

Again: The pitch change only affects the choice of sampling rate for the output device of mpg123. It does not change the actual audio data in any way. When you pipe the raw data via -s, there's nothing the pitch command can do.
What you can do is to change the sampling rate on the receiving end.

mpg123 -q -s file.mp3 | lame -v -r -s 36.030 -m j - out.mp3
Assuming raw pcm input file
LAME 3.98.2 64bits (http://www.mp3dev.org/)
Resampling:  input 36.03 kHz  output 32 kHz
Using polyphase lowpass filter, transition band: 15613 Hz - 16000 Hz
Encoding <stdin> to out.mp3
Encoding as 32 kHz j-stereo MPEG-1 Layer III VBR(q=4)

This is exactly what the pitch in mpg123 would have caused if the piping of WAV would be trouble-free. Another appoach would be to resample with another program like sox in the pipe -- that's what pipes are for, in the end.
For dynamic run-time pitching to work, one would need to add functionality to mpg123 to really resample the data. I'm not sure if mpg123 really needs that functionality.


Alrighty then,

Thomas.