Andrew Morton wrote: >Takashi Iwai <tiwai@xxxxxxx> wrote: > > >>a few months ago before 2.6.0 was released, i tested the audio latency >>with different kernels. the result was shown in the internal >>conference in SUSE, and i totally forgot to release the data until now >>:) >>maybe it will show you other aspects. >> >>here you can find the slides >> >> http://www.alsa-project.org/~iwai/audio-latency.pdf >> >> > >OK. How is the suse 2.4 kernel patched in these tests? A form of the >low-latency patch? > >I made some latency improvements to 2.6's ext3 recently, so it should be >performing significantly better than it was in 2.6.0-test9. > >I'll do some more checks on 2.6 but as far as I know, it's performing OK. >If Jack is indeed running with realtime policy I'd be suspecting that >something other than the normal spends-too-long-in-the-kernel problem is >occurring. > >Could someone give me a really simple description of how to obtain Jack, >and how to get it going sufficiently to demonstrate these problems? > >Thanks. > > > > Go to |/usr/src/linux/include/linux| (or wherever you have your kernel sources) and in the file |capability.h| change the line #define CAP_INIT_EFF_SET to_cap_t(~0&~CAP_TO_MASK(CAP_SETPCAP) to #define CAP_INIT_EFF_SET to_cap_t( ~0 ) and the line #define CAP_INIT_INH_SET to_cap_t(0) to #define CAP_INIT_INH_SET to_cap_t( ~0 ) Also make sure CONFIG_TMPFS is turned on. You must then recompile your kernel. put this in /etc/fstab (you may have to ceate the folders) shmfs /dev/shm shm defaults 0 0| none /tmp/jack tmpfs defaults 0 0 ||none /mnt/ramfs tmpfs defaults 0 0| Get jack at http://jackit.sourceforge.net/ do a ./configure --with-default-tmpdir=/mnt/ramfs --enable-capabilities make make install http://jackit.sourceforge.net/docs/faq.php is a good explanation of everything anyway.. I start jack as a user with $jackstart -R -v -d alsa -d hw:0 but if the compatability.h wasn't altered then you can start jack as root with #jackd -R -v -d alsa -d hw:0 There's an explanation of commnad line options at http://www.djcj.org/LAU/jack/ I think that's everything. I got xruns by opening programs but my audio tools are rezound and ardour and they won't record much longer that 20 seconds before jack xruns. I was the original poster. I found that if I used the 2.4.2 kernel with the low-latency patch from http://www.zip.com.au/~akpm/linux/schedlat.html#downloads and then installed jack as above, I would get NO xruns using kde, ardour (has multiple windows) and a network going. I've tried 2.6, 2.6.1 and patched to -mm4 and mm5 but I get xruns within even fluxbox by doing the most labour-unintensive computer tasks. The -p option extends the buffer (is that the word?). Well, I didn't need it with the 2.4.2 but in the 2.6 I made it -p 8192. It only extended the xrun relief by a couple of seconds though. (ie it did jack all) If you could throw any light on this then that would be absolutely great. ||
