On Mon, Jul 15, 2013 at 9:42 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 15 Jul 2013, Clemens Ladisch wrote: > >> > The interrupts shouldn't differ by more than the duration of one URB, >> > which would be 1 ms. There is an initial delay when a stream is first >> > started, which generally lasts 5-10 ms. But I think that hasn't >> > changed since the 3.5 kernel. Would it make any difference? >> >> The initial delay does not really matter as long as it's the same for >> both streams. (A difference of 1 ms would be significant if the period >> size is that short.) >> >> > Bear in mind that the input and output streams are started at totally >> > different times. >> >> Jack takes great care to start them together. > > If both streams are started at the same time then the initial delays > won't differ by much more than the endpoint periods. For audio, the > periods all seem to be 1 (either 1 frame or 1 microframe, depending on > the device's speed). So I guess this should not be an issue. > > My remark above refers to some of the usbmon traces provided during > earlier testing. For example, this one > > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1191603/+attachment/3714903/+files/1.mon.out > > shows the output stream starting at timestamp 3752849102 and the input > stream starting at timestamp 3753752104, about 900 ms later. Of > course, it's possible that James told JACK to start them separately. > >> > And anyway, James's latest problem occurs even with playback only. >> >> On my machine, 3 x 8 frames works, although Jack often complains that >> two periods are already completed when it expected only one. Anything >> less (2 x 8 frames) does not work; and 8 frames is where even my PCI >> card begines to make problems. >> >> In any case, "poll timeout" would not indicate completion delays but >> that no data was transferred _at all_. In theory, this should not be >> possible. I'm stumped at the moment. > > The odd thing is that that at least one of the usbmon traces showed the > audio streams getting shut down almost as soon as the audio-in started > -- after only the first one or two URBs have completed. That might > explain why the poll was timing out. But why were the streams stopped? > > James, did you ever provide a usbmon trace for 3.8 doing playback only > and using 64 frames/period? I don't recall seeing any. It might help. > OK - will send it to you off-list. James -- 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
