1 Aug 2011 05:39
EeePC 1005PE microphone is "stereo only", silent in mono
Pavel Roskin <proski <at> gnu.org>
2011-08-01 03:39:45 GMT
2011-08-01 03:39:45 GMT
Hello! I have discovered that the microphone on my ASUS EeePC 1005PE only works in stereo. If recording in mono, the result is inaudible. When I open the stereo recording in audacity, I see that the two channels are in counterphase. If I convert stereo to mono in audacity, I get a straight line, and it's inaudible when played. The driver itself requires stereo recording: $ arecord --rate 44100 -D hw:0 -f S16_LE --channels 1 >test.wav Recording WAVE 'stdin' : Signed 16 bit Little Endian, Rate 44100 Hz, Mono arecord: set_params:1065: Channels count non available However, pulse audio doesn't enforce it. So it's possible to record a mono file through pulse audio, and it's inaudible. Some programs simply assume a mono microphone and thus get no sound. I can work it around by setting the level on one of the channels to 100% and to 0% on the other in alsamixer. However, the GNOME volume manager removes that imbalance when adjusting the input level. I would prefer to have a robust solution. Perhaps one of the channels should be inverted. Or maybe the difference between the channels should be reported as mono input. I don't really care about stereo input. I'm using Linux 3.0 on Fedora 15. I checked out and tested the master branch of sound-2.6.git, and it has the same problem. It looks like the problem is known. I found this comment in alc882_quirks.c:(Continue reading)
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