From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Barton-Davis Date: Thu, 28 Oct 1999 14:45:09 +0000 Subject: Re: Sync Issues (was Re: External MIDI Sync using OSS/Free) Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sound@vger.kernel.org > What lowlatency patches?? kernel patches?? That's just ugly. Where >can I get them? not ugly! the kernel folks, well Ingo Molnar in particular, recognized that the kernel wasn't well tuned for low latency requirements. Ingo believes that his patches will be in kernel 2.4. look at http://www.gardena.net/benno/linux/audio for more details. > How can you tell if you've underrun under OSS? Using ALSA, I guess you >can use it's time stuff to calculate if you've missed a frame, but even >that seems hacky. no, ALSA has an ioctl to tell you if had underruns or overruns. its The Right Way (TM). OTOH, i haven't written any audio programs that ever use it, because I write them so that if I did have an {over,under}run, it would mean that some totally catastrophic has happened. maybe i don't write the right kinds of applications :) > I don't like using one dsp as the sync master since I always want to be >able to sync to something external, like MIDI. if you mean MTC, this simply isn't accurate enough for syncing soundcards. you can use MTC as a master clock for tempo, but between MIDI clock messages you will still have to be prepared to do the actual syncing of soundcards. Given that a MTC messages take on the order of 1ms to arrive (!), its not a high-quality sync source. so, i don't think you can "sync soundcards" from MIDI. You can use MTC to help inform your own sense of the forward passage of time and to dictate MIDI-related tempo, but thats not the same thing that Benno was talking about. --p