On Fri, 26 Jul 2013, James Stone wrote: > >> James, can you try this out and send me the usbmon trace? At 64 > >> frames/period this should end up using 4 URBs, which is the minimum > >> requirement if there are no more than 8 packets per URB and an > >> incompletely filled URB can contain as few as 1 packets. With this > >> patch, there should be no difficulty going down to 32 or maybe even 16 > >> frames/period. > >> > >> > > > > Here you go.. (attached). This is at 64 frames/period. > > > > James > > Apologies - that was with 3 periods/buffer. 2 periods/buffer attached.
It doesn't make any difference; the ALSA driver ignores the periods/buffer setting when interacting with the USB stack. One thing that does make a difference, however, is that you changed from 44100 Hz to 48000 Hz. That's okay; it's still a valid test. Anyway, the traces show that the patch works as desired, but it isn't optimal. The optimal number of URBs is actually quite tricky to calculate. I'll send out another patch in a few days. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
