On Tue, Aug 12, 2008 at 9:16 AM, Clemens Ladisch <cladisch@xxxxxxxxxxxx> wrote: > "universal serial bus bus"? ;-) Yes, in France, it is usual to say "bus USB", because in many minds (mine only ?) USB do not relate to a bus, but to a technology (which is wrong, of course), sorry for the mistake ! :) >> sample rate. > > USB doesn't have a built-in sample rate; audio samples are transported > in packets. Yes. I am interested by the frequency at which these packets are send. > USB does have a bit rate and a frame rate, but neither of these can be > changed. I think that I was talking about the frame rate, sorry ! In fact I read a post on another list that I could report here : -- First of all - USB based sound cards are notoriously terrible for temporal accuracy. Your best bet really is to get an PCMCIA-based card. The reason is, the data bus of the USB is not all that fast - it's high bandwidth, but has a slow sample rate - default is only 125 Hz. This means you can only "deliver" a sound to begin roughly every 7.5 ms... So if the sound delivery from the hsystem does not line up appropriately, you will have a gap while it "waits" to sync w/ the USB data bus. Now there is hope! In Windows, you CAN change the USB sample rate, using an applet. This one here will do it: http://www.softpedia.com/get/Tweak/System-Tweak/USB-Mouserate-switcher.shtml It allows changing the data rate up to 1000 Hz (1 ms resolution). Note - this changes the access rate for ALL USB devices; mice, remote drives, access keys, etc. It may also decrease the time you get out of the battery, due to larger power consumption. -- > The only exception is the frame rate on UHCI controllers; to > change the frame length, change the initialization of the USBSOF > register in the configure_hc() function in uhci-hcd.c. > > > Why would you want to do this? I did not try this applet, since I do not use Windows, but I was wondering if it was possible in Linux. However, I don't think that altering the kernel code is a good idea (for me) ! :D Regards, Adrien _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
