On Fri 26 October 2012 15:21:06 Jeffrey Barish wrote: > 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. To conclude (?) this thread, I am now convinced that the anomalies I observed were unrelated to the device driver. I had two theories remaining. One was that the problem was somehow related to an overheating problem. I used a heat gun to convince myself that the theory was wrong. The other was that the problem had something to do with services running in the background that interfered with the device driver. I removed or disabled all services that I could identify as superfluous. Removed services include zeitgeist, apparmor, modemmanager, mdadm, and bluetooth. Disabled services include atd, dns-clean, and pppd-dns. The system has been running perfectly with an 88.2 kHz sample rate and no external USB hub for 2 days. However, I tried booting the system with a copy of the OS from before I removed superfluous services. It still ran perfectly. Thus, I cannot convince myself that removing superfluous services actually solved the problem. I suppose it's possible that some service was running sporadically, which could explain why the problem seemed to come and go and also why the problem did not occur when I booted the copy of the OS. As long as the problem remains dormant I have no alternative but to move on and see whether the problem eventually recurs. Only time will tell. Thanks for all the help. Hey, I built a kernel and got my own version of the device driver to run. That was exciting. -- Jeffrey Barish ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_sfd2d_oct _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
