> Date: Sun, 16 Feb 2014 14:56:08 -0800 (PST) > From: Bill Unruh <unruh@xxxxxxxxxxxxxx> > To: Samuele Carcagno <sam.carcagno@xxxxxxxxx> > Cc: alsa-user@xxxxxxxxxxxxxxxxxxxxx > > On Sun, 16 Feb 2014, Samuele Carcagno wrote: > > > On Sunday 16 Feb 2014 20:47:44 you wrote: > >> 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. > > > > yes, that's correct. Because aplay does play the wav file well after it is "primed" > > by playing some sounds with PyAudio, I wonder what PyAudio is doing and whether > > I could instruct aplay to do the same through some command-line option. > > > > Just for completeness I should add that I observed this behaviour with the soundcard > > plugged on different computers, as well as with the Debian testing branch and the current > > Ubuntu development branch. I removed pulseaudio before running any of these tests as it has other > > problems for me: > > > > http://lists.freedesktop.org/archives/pulseaudio-discuss/2012-October/014756.html > > > > Probably I can circumvent the onset/offset transient issue with a function that automatically > > plays some sounds with pulseaudio each time my pyqt4 program starts. I will also have to check > > that the soundcard plays sounds with 24-bit depth. > > It definitely sounds like a problem with your soundcard. > What happens if you put in say 1 sec of silence before the sound starts > playing. > Mind you that trailing DC really looks suspicious, as if your file has a DC > component, rather than the soundcard, but is belied by the fact that if you > play it later, it is fine. The DC looks like it is dying away at the > beginning, but then it sure should not be there at the end. I agree there's something very odd about the DC segments before and after the tone burst. I think I can just barely see the 10ms fade-in/out. It's a little more apparent when zoomed in. The DC segments look like maybe switching transients while the card is being initialized. Perhaps playing a short piece of silence via PyAudio before playing your real content via AlsaAudio would be the most practical solution for that situation. One other thing I remembered about PyAudio with my program is I see a lot of whining about 'Unable to find definition ...', 'No such file or directory', 'Unknown PCM rear', 'Failed to create secure directory: Permission denied', and so forth with PyAudio during program initialization. With AlsaAudio, there is no such complaining. HTH Robert ------------------------------------------------------------------------------ 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@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
