On Sat, 14 Nov 2009, Javier Kohen wrote: > > I tracked a problem I'm having with my USB audio DAC down to > > patch cb88a1b887bb8908f6e00ce29e893ea52b074940. Are you certain? That patch did not change anything important; mostly it just renamed some functions. > > This issue is present in kernels 2.6.30.6+, 2.6.31.* and 2.6.32-rc7. > > > > With this patch applied, some combinations of two programs communicating > > with the DAC cause the audio to vanish. The only way to restore it seems to > > be to close all applications that have the DAC's devices open. After this, > > all goes back to the previous functional state, though the bug can be > > reproduced again by following the same steps. > > > > All audio applications I have use ALSA directly. I'm not running PulseAudio, > > ESD or any other kind of audio daemon. I don't have other sound cards in the > > system, except for the motherboard's on-board, which is disabled from the > > BIOS. Some easy ways in which I can reproduce this problem: > > > > 1) Start playing sound with totem/gstreamer, or sox' ALSA driver (run "play" > > from the command-line). > > 2) Start alsamixer. Boom, the device goes silent. Can you post a usbmon trace showing what happens when you run this test? > > ALSA recognizes the DAC as "Burr-Brown Japan PCM2702." Currently this DAC is > > connected to my computer through the USB hub in my monitor, which makes it > > go through the EHCI driver. When connected directly to the motherboard the > > DAC uses the OHCI driver, which doesn't exhibit this problem. However, there > > is a problematic interaction between the DAC and the OHCI driver or > > motherboard chipset (nVidia's CK804), which causes the audio to degrade > > after a while. The degradation appears first as a background hiss, until it > > turns into a "broken radio" kind of sound. If anyone would like to track > > down the problem with OHCI, I'm more than willing to give further details > > and assistance. My intuition tells me this is an USB issue, not ALSA's. In any case it's a separate matter, since it involves OHCI and not EHCI. Alan Stern -- 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
