On Fri 26 October 2012 21:47:05 Daniel Mack wrote: > 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. > Which kernel did you use when you heard the 'blibs'? The latest news is bad. I am on 3.2.0 now. The USB DAC is working perfectly at this moment at both 96 kHz and 88.2 kHz without the external USB hub (imagine calling that bad news). If I set the srate to 88.2 kHz and stop and start the sine wave, sometimes I get the blip. Forget about its being periodic. It was definitely periodic before lunch; now I usually get random intervals if I get any blips at all. As I am typing this message, I can't get blips at all. There was some correlation between changing sample rates and blips, but I can't reproduce that behavior now. What is most weird is that I haven't gotten any ticks since lunch with any kernel or with either sample rate, yet they were reliable earlier today unless I used the external USB hub. I obviously need to experiment some more to see whether I can observe a pattern. -- 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
