[pulseaudio-discuss] issue of remap_channels mapping stereo to mono
long.bu at intel.com
Thu Dec 17 07:30:38 PST 2009
Scenario: can't capture which PA in mono format with Analog ALC272 codec.
Root cause: The h/w only works as stereo, so remap_channels remap stereo to mono by simply add one channel to another. Unfortunately, the 2 channels are 180 degree phase different so the sum is always very very close to zero.
But Mono capture works fine with pure alsa at the same platform without PA. I looked at the pcm_route.c of alsa-lib, it also just simply add two channels with some weight for each channel. Anybody can tell me what magic is done by ALSA before I have to dig into the code? :-). Did I miss something?
Or what is the general solution to solve this. I am considering some way
To detect the phase difference of channels.
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