After a number of years of making successful music recordings using a combination of rosegarden and ardour on my Ubuntu Dapper Drake system, and my home grown real-time kernels, I thought it was time to upgrade to Hardy Heron and use the proper real time kernel that the experts had built. What a disappointment! I have an internal pci sound blaster live card (emu10k1 chip set) and a M-audio audiophile USB sound module. On my dapper installation, which happened to have 2.6.22.1 real time patched kernel (the default ubuntu kernel was 2.6.15), I could get latencies as low as 1.5ms (32 frames/period) on the sound blaster and 2.7ms ( 64 frames/period) on the USB Audiophile with very few xruns; so few xruns that I used to wonder why people posted to mailing lists/forums about the problem. With the stock Ubuntu 2.6.24-21rt kernel the sound blaster gives xruns every few seconds with no load (no recording and no playing back) at 23ms latency (512 frames/period) and the Audiophile struggles at 43ms ( 1024 frames/period); I am getting xruns every 10-20 seconds. Infact the rt kernel gives little, if any, improvement over the generic kernel. I have the following settings in my limits.conf @audio - rtprio 95 @audio - memlock 512000 @audio - nice -19 And I have a script to set the real-time priorities for the interrupts for the interrupts that the sound system use - usually IRQ17 and IRQ19. My user is also a member of the audio group. I have tried the nohz=no on the kernel start up command line as discussed in numerous fora with no change. I did not expect one: johnt@TOMO001:/boot$ grep NO_HZ config-2.6.24-21-* config-2.6.24-21-generic:CONFIG_NO_HZ=y config-2.6.24-21-rt:# CONFIG_NO_HZ is not set I have also tried the changes described in: http://alsa.opensrc.org/index.php/Usb-audio which also made no difference. Any ideas what to try next? Have I got to go back and start build my own kernels again (which always involved a battle between me and the nvidia graphics card)? John Tomlinson _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
