On 26.10.2012 21:43, Jeffrey Barish wrote: > 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.
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