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I want to downsample an existing audio file to 8KHz mono. This command line downsamples it to stereo:

mplayer -quiet -vo null -vc dummy -af volume=0,resample=8000:0:1 -ao pcm:waveheader:file="/tmp/blah1.wav" ~/from_my_cellphone.3ga

It generates a file that the file utility identifies as stereo:

$ file /tmp/blah1.wav 
/tmp/blah1.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, stereo 8000 Hz

Now, if I read the documentation correctly, I should add pan=1:0.5:0.5 so I get a file that's half the size:

mplayer -quiet -vo null -vc dummy -af volume=0,resample=8000:0:1:pan=1:0.5:0.5 -ao pcm:waveheader:file="/tmp/blah2.wav" ~/from_my_cellphone.3ga

But it doesn't! blah2.wav is identical to blah1.wav! What am I doing wrong?

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