I guess the right place to fix the issues mentioned in my original post is in snd_usb_init_substream() in urb.c:
case USB_ID(0x0763, 0x2081): /* M-Audio Fast Track Ultra 8R */ subs->ops.prepare_sync = prepare_playback_sync_urb; subs->ops.retire_sync = retire_playback_sync_urb;
I've tried combinations using the _hs and _emu versions of the retire.../prepare... functions. It either didn't change anything or made it worse. I guess we need _ftu versions.
Could somebody at least tell me how to find out what's exactly going wrong with the sync. Can I find something useful monitoring the urbs in Windows?
Please, help me. We're so very close to full support of these devices, but I don't know how to proceed.
Thanks in advance,
Felix
Am 25.09.2010 11:57, schrieb Felix Homann:
Hi,
in that past months I've been trying get the Fast Track Ultra devices working properly in Alsa. We've had lots of progress, most of the code has moved to Alsa git and today I've even posted a patch for getting mixer support for these devices.
Now, I need to get some expert's advice: The devices seem to drop samples or frames. Here's a report I've got today on the M-Audio forum:
"I've got a subtle problem to report: I think audio playback is dropping sample frames. To hear the problem, open Audacity at 48 kHz and play a 10-kHz. sine wave. When I do that I hear a regular clicking sound, about four clicks a second. I've tried recording the output and if I'm seeing correctly, exactly one sample frame in every 13312 (13x1024) is being dropped on output. I don't see anything similar on input. When either jack or Pd has both the input and the output open, the delay from input to output gradually decreases until it forces occasional sync errors. (I haven't tried this with audacity though.)"
(see http://forums.m-audio.com/showthread.php?714-Not-a-problem.-FastTrack-on-lin...)
I could reproduce it on my machines, even at 44.1 kHz. The clicking sound is very subtle, it goes unnoticed when not listening to pure sines without attention to clicks.
How can this be sorted out. Any ideas?
Kind regards,
Felix _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel