I have never seen that in any of the files I have played. That hints that that is your input stream, rather than some problem with the soundcard itself, although I have also never used your sound card.
So to be clear, you recorded onto a .wav file that sound. That .wav file did not have those transients. You then played that file with aplay, and recorded the output, starting the input before the file started playing and ending after it stopped. If so, that is one strange soundcard. On Sun, 16 Feb 2014, Samuele Carcagno wrote: > >> >> Coincidentally, I just finished doing some coding for PyAudio and >> (py)alsaaudio on Debian 7/Wheezy, though I don't use PulseAudio. >> I also found that PyAudio has pops and clicks characteristic of >> Xruns (overruns and/or underruns), while AlsaAudio does not. >> (FWIW, I decided to use AlsaAudio rather than PyAudio, though I >> coded my program with a constant that makes it trivial to switch >> between the two.) > > Yes, I've noticed this problem with PyAudio with other soundcards as well. >> >> In another reply, Bill Unruh suggested routing the output through >> the line input of another card. That is a very good idea and may >> give you an idea of what's happening with the pops and clicks in >> the middle of the file with PyAudio. > > Thank you and Bill for the suggestion, I did that and it looks like > there is a DC offset before and after the sound starts playing, you > can see it on this graph: > > https://dl.dropboxusercontent.com/u/1162239/before_pyaudio.pdf > > this was obtained by playing a 500-ms 1 kHz pure tone with 10-ms > fade in and 10-ms fade out (not obvious from the figure but the fade > in and fade out is there) with aplay > > after I "prime" the soundcard by playing some sounds with pyaudio, > the graph obtained by playing the same sound with aplay looks like this > instead: > > https://dl.dropboxusercontent.com/u/1162239/after_pyaudio.pdf > > Sam > > ------------------------------------------------------------------------------ > Android apps run on BlackBerry 10 > Introducing the new BlackBerry 10.2.1 Runtime for Android apps. > Now with support for Jelly Bean, Bluetooth, Mapview and more. > Get your Android app in front of a whole new audience. Start now. > http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk > _______________________________________________ > Alsa-user mailing list > Alsa-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/alsa-user > -- William G. Unruh | Canadian Institute for| Tel: +1(604)822-3273 Physics&Astronomy | Advanced Research | Fax: +1(604)822-5324 UBC, Vancouver,BC | Program in Cosmology | un...@physics.ubc.ca Canada V6T 1Z1 | and Gravity | www.theory.physics.ubc.ca/ ------------------------------------------------------------------------------ Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
