On Wed, 10 Dec 2008, stan wrote: > Paulo Moura Guedes wrote: >> I'm trying to get bit perfect output out of my linux box, but I can't What is "bit perfect output"? Sound output is an analog process ( sound waves in the air are analog). You do know that you can just copy the sound file whereever you want. >> find much >> info on the web. I'm using ALSA. >> >> >> Some questions: >> >> >> - does Linux/ALSA features dynamic sample rates? > yes. You can specify whatever rate you want and it will > happen. eg 57,325 frames/second. And that produces lots of distortion and noise. Resampling of any digital signal does that. There are some highly inefficient (ie, take lots of computer time) process which can minimize that. (see for example www.theory.physics.ubc.ca/soundcard/resample.html for a test of the various sox algorithms. the good ones are slow. ) Not sure what you mean by "dynamic sample rates". >> - is it possible to set the bit-depth? (in my case to 24 bit) > yes, but your card has to support it. Most new cards have > internal processing larger than 24 bits >> - what other variables do i have to consider in order to get bit >> transparent ouput, >> i.e., no resampling at all? > Use only hardware rates supported by your card. You can > ensure this by using plughw as your device instead of > default. That converts from the audio application sound > format to the sound card internal format, but does no > resampling. You can avoid even the conversion if you make > sure the audio is in the format that your sound device uses > internally. >> - is it possible to check if ouput is bit-perfect? > Where do you want to check. It will be difficult to check > internally to the card. And unless you are outputting to > digital and can capture the output from the sound device, > you won't be able to tell. > > From alsa-lib to the driver you should be able to check by > modifying the library call for your particular card to > include some sort of save or monitor, but that is probably > redundant. > > It sounds like you should be looking at the alsa-lib API at > http://www.alsa-project.org > > ------------------------------------------------------------------------------ > SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. > The future of the web can't happen without you. Join us at MIX09 to help > pave the way to the Next Web now. Learn more and register at > http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ > _______________________________________________ > Alsa-user mailing list > Alsa-user@xxxxxxxxxxxxxxxxxxxxx > https://lists.sourceforge.net/lists/listinfo/alsa-user > ------------------------------------------------------------------------------ SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada. The future of the web can't happen without you. Join us at MIX09 to help pave the way to the Next Web now. Learn more and register at http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
