On Tue, May 11, 2010 at 05:48:11PM +0100, Pedro Ribeiro wrote: > I'm clueless about the whole underlying process but I don't think it > is related to playing a file from the disk or another USB device. > > I don't need to play any file for this interference to be heard - I > just need to "open" the device. By this I mean that if I create a JACK ... which will stream zeros. Sure, that should also trigger the bug then. > server or if I open the device using the ALSA backed in a program like > Mixxx I immediately start hearing the cracks and pops in the speaker. > But to answer your question, playing a file from the hard drive using > aplay I can also hear the interference - but only when the sound is > playing. As soon as the sound stops and the audio device is "closed", > no interference occurs. Yes, because the stream is stopped, pending URBs are unlinked etc. That's completely expected. > However, when using the JACK server, which probably opens and polls > the audio card constantly (its a low latency audio server) I don't > even need to be playing any sound for the interference to be constant. That shouldn't affect the driver itself but just put the ALSA core under pressure. > I can also see it since I have 4 output leds in the USB audio card and > even if I'm only using 2 channels, the 4 channel leds light up with > interference as the sound cracks and pops. No surprise here. The 4 channels are mux'ed in an interleaved fashion, so if the buffers contain rubbish, you will hear artefacts on all channels. Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
