On Wed, 4 Jul 2018, R0b0t1 wrote: > On Sun, Jul 1, 2018 at 9:12 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, 30 Jun 2018, R0b0t1 wrote: > > > >> The problem seems more noticeable when using the Python libusb > >> bindings but it still exists when using libusb directly. Can anyone > >> suggest what to look into? > > > > Have you tried using usbmon to capture the data as it is received by > > the kernel? > > > > Thank you for the suggestion. Having looked at usbmon output it > appears the kernel is receiving all zero packets for some transfers. > It also looks like some packets are dropped, but I am not sure how to > tell. Are blank transfers dropped data also? It would help if you posted a few examples. Isochronous packets are different from other kinds; to interpret them properly you need to look at the frame descriptors. > If I try to reconstitute the audio stream by ignoring all zero packets > the stream still experiences pops and clicks though they are much > quieter. That is the best indication I have that packets are being > dropped. The discontinuities in the waves lead to the pops and clicks. There are a few reasons why isochronous packets may get dropped. Possibly the host driver did not ask for them in time. And possibly the peripheral wasn't able to send them in time. Alan Stern -- 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
