Hi Daniel,
On Fri, 16 Nov 2012, Daniel Mack wrote:
On 16.11.2012 05:32, Daniel Griscom wrote:
At 10:02 PM +0100 11/15/12, Eldad Zack wrote:
I'm not an ALSA dev, but I recently posted a series of patches for the M-Audio Fast Track C400, which uses the implicit feedback code that was already in the tree for other devices.
Yes, sorry for not responding. I've seen this, but didn't have time yet to respond. Thanks for doing this.
Thank you for doing the heavy lifting there! After I noticed the clock drift (and read about the implicit feedback mechanism) with the first version I posted, I was able to get my hardware to work properly thanks to your work.
BTW, I took some measurements with a slightly modified jack_delay (to collect per-period statistics and more decimal precision output) and I see +/- 1 usec variation in real-world latency, so I'm very happy with it so far.
Note that I never tested the automatic discovery of that mode. The device I wrote the code for doesn't announce it that way, and so a quirk was needed in pcm.c to make it happen. Ideally though, what you did is the right thing to do, just just need to make sure the driver really obeys that setting :)
I think that Autodiscovery should fail with this amtel device because the number of endpoints is 1 for the playback ep (this is what I encountered with the C400). Maybe a info message could be added in case the attributes do say implicit feedback, but bNumEndpoints < 2?
Cheers, Eldad