Martin Gagnon wrote: > > > > I know this is a software-focused group for audio, but many of you may > know a thing or two about USB protocol messages to a USB audio device. > > > > Here is the situation, we’re dealing with a C-Media audio device > CM6206, using MS usbaudio.sys driver. The C-Media chip is sitting > behind a NEC USB2.0 hub that’s connected to a NEC USB2.0 host > controller, itself connected to a PLX PCIe switch. Using Windows XP > SP3, the driver installs fine, typical audio playback works fine > (directsound or wave output). However, when we concurrently enable > video and audio, for example playing back a movie in full screen, with > no hardware video decoding, we lose audio after “a while”, and can’t > get it back. However, the Windows default sounds (for example system > beep or logoff sounds) are still working fine. The interval of time > before we lose the audio varies with the graphics activity in the > system, as well as with various systems of various speeds, so it can > take 5mins or it can take 1 day. We tried the C-Media driver as well > and got the same symptom. We also tried different USB audio chip > manufacturers (including TI) to no avail. > So, is endpoint 2 the "sync" endpoint for the audio out data on endpoint 0x86? > So we looked at the USB transactions on the USB bus going into the USB > audio chip. We note a series of OUT transactions followed by IN > transactions, usually containing a “NACK” message. This goes on for as > long as the audio plays back fine. Then we get a series of OUT > transactions with no corresponding IN transactions, then we get a > Reset event. > Did you notice that the final OUT transaction is damaged? Is that typical of the captures you've seen? Is the NEC hub a constant in all of this? -- Tim Roberts, timr@xxxxxxxxx Providenza & Boekelheide, Inc.