On Sat, 2011-02-12 at 13:44 -0800, AW wrote: > Devin Heitmueller <dheitmueller@xxxxxxxxxxxxxx> wrote: > > > When I use this command simultaneously: > > > arecord -D front:CARD=PAL,DEV=0 -f S16_LE -c 2 -r 8000 /aux/tmp/bla.wav > > > I get correct audio with strong noise: > > > http://www.wgboome.de./bla.wav > > > (it is from input=1 for copyright reasons... so there is silence plus > noise) > > > > The "-r" argument should almost certainly be 48000, not 8000. > > > Maybe... > That device is rather old... > And i didnt tell pactl anything about sample rate... I find audio at 8 ksps very unusual for a TV capture device. > With the filter from the appendix the noise is gone... > But it feels like a dirty hack, because it would cut out (overly?) loud noise, > 2... > > My wild guess is, that the usbaudio driver injects some bad samples > (0x8000..0x9000) every appr. 256 bytes... I looked at the data. It is mostly hovering around 0, but you have bursts of very negative values periodically: (These values are shown as little endian, so swap the bytes to consider the value) 0000630: faff fdff f9ff fbff 1080 1080 1080 1080 ................ 0000640: 1080 1080 faff fbff 1080 1080 8888 8888 ................ 0000650: 1080 1080 fbff fcff fbff fcff fdff fdff ................ ... 0002fe0: 0000 0000 0100 0100 ffff 0000 1080 1080 ................ 0002ff0: 1080 1080 1080 1080 1080 1080 1080 1080 ................ 0003000: 8888 8888 0100 0000 ffff ffff 0000 0000 ................ 0x8010 is -32752 and 0x8888 is -30584. The data set contains no large positive values (nothing in the range 0x1000-0x7fff). The valuex 0x10 and 0x80 do remind me of the YUV values for black: Y = 0x10, U = 0x80, V = 0x80. Maybe some video data is getting thrown in with the audio? Regards, Andy > -Arne > > appendix: > #include <stdint.h> > #include <unistd.h> > > int main() { > uint16_t buf[1000000]; > const int r = read(0,buf,sizeof(buf)); > for (int i=0; i*sizeof(*buf)<r; i++) { > if (buf[i]/256>=0x80 && buf[i]/256<0x90) continue; > if (write(1,buf+i,2) != 2) break; > } > return 0; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
