[MPlayer-dev-eng] [PATCH] AF Pitch filter

[Charlie Brej]

I wrote a pitch filter for mplayer (Audio timescale-pitch modification).
The patch is attached. It works using a FFT. For the FFT code I used the
Kiss FFT (which comes under a BSD licence and is already a part of some
other projects such as speex). I realise there are FFTs already in
mplayer but I was not sure how to link to them from libaf. The FFT code
can be used for low/high pass filters etc.
The pitch filter itself takes an operand to effect the pitch of the
audio. The lower the number the higher the pitch. The reason for this is
to correctly balance the pitch with the speed of playback. To observe
the effect run:
  > mplayer movie.avi -af pitch=1.5 -speed 1.5

You can hear some examples of the effect at:
http://www.cs.man.ac.uk/~brejc8/mplayer/

The code is not complete as it does not have some more advanced features
such as phase adjusting. I have tried implementing these too but was
having too many problems getting it to work. Still works reasonably well
without it.

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