On Thu 25 October 2012 19:10:45 Daniel Mack wrote: > On 25.10.2012 17:18, Jeffrey Barish wrote: > > I found something in the snd_usb_audio code (in endpoint.c) that could > > explain one of the problems I have observed (the ticks). I would > > normally test my theory by modifying the code. In this case, I would > > like to stick in a print statement to see what values are being assigned > > to certain variables. Unfortunately, I am too ignorant to do something > > even this trivial as I have never worked on kernel code. I think I am > > supposed to use printk, > > printk is nice for simple debugging, yes. But note that this call is > timing critical and should not be used in "fast path" code. Introducing > a printk for each received packet for example will almost certainly make > the driver behave quite differently. > > > but beyond that I am lost. Can someone provide > > me with some directions? I need to know how to make the driver. To that > > end, I probably will have to install additional packages. After making > > the driver, I need to know how to install it over the existing driver. > > Here's one way to do it: > > 1. git clone > git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git (your > patch should apply on top of this tree eventually) > 2. cd sound > 3. zcat /proc/config.gz >.config > 4. build and install the kernel image. How that is done depends on the > distribution you're using. For Ubuntu follow the docs at [1] (start at > point #5). For Fedora and others, something like "make && make install" > should do > 5. reboot and check that the new kernel is running > 6. hack on sound/usb > 7. make M=sound/usb > 8. reload the module with "sudo rmmod snd_usb_audio; sudo insmod > sound/usb/snd-usb-audio.ko" (better plug out the device before so you > always have the same defined point of start) > > > Hope that works for you. > > > Daniel > > [1] https://wiki.ubuntu.com/KernelTeam/GitKernelBuild Your directions were almost perfect, so even I was able to build the kernel. I made a discovery using the new kernel that might help someone more familiar with the code than I am to localize the problem. I am still hearing the blip when I play audio sampled at 88.2 kHz, but I just noticed that the blip is perfectly periodic, with a period of about 16.4 seconds. I am playing a sine wave synthesized using GStreamer using the following command: gst-launch audiotestsrc volume=0.01 ! audio/x-raw-float, width=64, rate=88200, channels=2, endianness=1234 ! audioconvert ! alsasink A sine wave makes it easier to hear the blip. Does this clue suggest anything? I also want to mention that when I use the new kernel, I do not get the ticks at either 88.2 or 96 kHz even when I do not use the external USB hub. I plan next to back up to the 3.6.2 kernel to see whether I still get ticks there. -- Jeffrey Barish ------------------------------------------------------------------------------ WINDOWS 8 is here. Millions of people. Your app in 30 days. Visit The Windows 8 Center at Sourceforge for all your go to resources. http://windows8center.sourceforge.net/ join-generation-app-and-make-money-coding-fast/ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
