Re: [Alsa-user] OT? - Using a test tone to set correct signal levels
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From: Sergei S. <ste...@li...> - 2006-07-20 15:55:37
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On Thu, 20 Jul 2006 08:32:37 -0700 (PDT) Bill Unruh <un...@ph...> wrote: > On Fri, 21 Jul 2006, Arthur Marsh wrote: > > > I had some problems with *some* .wav files distorting badly when played > > in xmms. > > > > To check to see if sound levels were clipping, I downloaded the > > executable from http://sourceforge.net/projects/wavb then added a > > missing library (libpng3), and was able to easily produce a 30 second > > sample of a 1020 Hz sine was 100 percent modulated as a .wav file. > > > > Playing this .wav file in xmms revealed that I needed to set the Input > > level of "Wave" for my EMU10K1 based card to 60 percent, in order not to > > have clipping if the output levels "PCM" and "Master" were set to 100 > > percent. (I used kmix, but alsamixer or similar would be fine). > > Not a good test. Instead check the level of the recorded sound ( eg with > sox) to see how high you need to set the input level to get clipping. > It could well be that the out is clipping even with a not-maximal sound. > > > > > It may be worth checking if one wants to eliminate distortion from > > signal levels being too high passing through the sound card. > > > > Or directly measure the distortion. Often at least on cheaper cards > distortion starts climbing long before clipping starts. > (eg www.theory.physics.ubc.ca/soundcard.html could for example be used. > Unfortunately it only uses the oss or alsaoss at present) > > > > > ------------------------------------------------------------------------- > > Take Surveys. Earn Cash. Influence the Future of IT > > Join SourceForge.net's Techsay panel and you'll get the chance to share your > > opinions on IT & business topics through brief surveys -- and earn cash > > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > > _______________________________________________ > > Alsa-user mailing list > > Als...@li... > > https://lists.sourceforge.net/lists/listinfo/alsa-user > > > It may be purely analog problem - for example, headphones have low impedance, so the amplifier can not drive enough current. -- Visit my http://appsfromscratch.berlios.de/ open source project. |