Re: why I cannot use C-Media USB Sound device when it's plugged on hub together with other devices?
- From: 张韡武 <zhangweiwu@xxxxxxxxxx>
- Date: Sat, 28 Oct 2006 03:34:31 +0800
于 Sat, 28 Oct 2006 03:03:01 +0800，张韡武写到：
Hello. I got a C-Media USB Headphone Set (a small USB Sound device).
1: if it's plugged directly on the USB port on motherboard (Intel
Corporation 82801EB/ER, UHCI+EHCI), it works. In /proc/bus/usb/devices it
shows this device is connected to UHCI Controller.
2: if it's plugged directly on the USB port on PCI-usb card (NEC
Corporation USB, OHCI+EHCI), it works. In /proc/bus/usb/devices it shows
this device is connected to OHCI Controller.
3: if it's plugged on a USB 2.0 Hub, and it's the only device plugged on
this hub, it works. Interestingly, if the hub is plugged to the USB port
on the monther board (Intel UHCI+EHCI), the hub is shown in
/proc/bus/usb/devices connected to a UHCI controller; if the hub is
plugged to the USB port on the PCI USB card (NEC OHCI+EHCI), the hub is
shown in /proc/bus/usb/devices connected to a OHCI controller;
4: if it's plugged on a USB 2.0 hub which already have other devices
plugged on (typically, a USB Mouse), it will NOT WORK. Any application
uses sound, be it ALSA or OSS app, simply hangs when it wish to play
sound. Interestingly, the hub is shown in /proc/bus/usb/devices connected
to a EHCI port, and the USB Sound device in turn connect to the hub.
It looks like if the sound card is connected to an EHCI controller, it
will not work.
I am pretty interested in this problem: if I wish to use this USB Sound
device on a hub which already have other USB devices plugged in, is it
possible? what should I do?
Further test seems to suggest this issue is not directly related to
OHCI/EHCI/UHCI, this issue is a bit random.
1) when USB Sound device is the only device plugged on HUB, it always work;
2) when USB Sound device is plugged together with with mouse on HUB, most
of the times it works; sometimes, it play sound for one second, hang for
another second, go on playing one second and keep this way; 3) when USB
Sound device is plugged together with USB Keyboard or together with one
USB keyboard and one USB Mouse on a HUB, most cases it doesn't work (hangs
the applications who try to play). But sometimes, when unplug the USB
Keyboard, the applications previously hanged up (for trying to play sound)
come back alive and go on playing sound.
It is strange, perhaps I better give up.
.
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