On Oct 11, 2007, at 2:45 PM, Jonatan Liljedahl wrote: > Jonatan Liljedahl wrote: >> I'm having problems with distorted sound with ALSA. It's not clipping >> distortion but more like a dirty spectra. >> The test I am doing is playing a pure 440Hz sawtooth wave, and the >> sound >> is very unclean, there's inharmonic partitials that shouldn't be >> there, >> actually below the fundamental frequency I think. Compared to an >> analog >> sawtooth oscillator it sounds really awful. > > Here's a picture of the resulting waveform when playing a pure > sawtooth > and recording it straight in again on my Terratec Phase 26. As you can > see, there is some kind of ringing happening... > > But, this is interesting, when recording a pure sawtooth from my > analogue modular into my soundcard (through a mixing desk) there was > some ringing too, but it didn't sound at all as dirty as the previous > computer-generated sawtooth. When playing back this recorded analogue > sawtooth, I had a hard time hearing the difference. > > So, I guess it's not the ringing this is about. And now when I listen > again with different frequencies I definitely hear that the > polution of > the spectra is subtones, frequencies below the fundamental. > Perhaps the problem is some cyclic jitter? But it seems dependent > on the > high overtones of the computer-generated waveforms since I can't > hear it > when recording a sawtooth from the outside... > > Any ideas what this is and what I can do about it?
My thinking from your last post was a bit depth or format mismatch. Whatever method used to create the saw, must be explicitly duplicated in your aplay command parameters. aplay does not detect anything for you, so you have to specify every parameter for the wav file including channels, format, bit depth, sampling rate. Looking at your pictures, the distortion occurs at the min and maxima of the waveform which would also suggest a headroom mismatch. You ever listen to a 24 bit file played back at 16 bit without dithering? Can be interesting... I was also going to say in the experiment, which can be a little more rigorous, to look at spectrum for comparison you need to do FFT. And there is no audible control - maybe play the file back on a system you know is working, not some other hacked linux box ;) Look at man aplay and make sure it has all the parameters exactly matching your input conditions in audacity - which you have not completely enumerated yet. What does your aplay command so far look like? You want me to write it for you? ;P -jonathan adams leonard ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
