Steve O'Hara-Smith wrote: > On Fri, 15 Jun 2007 21:09:24 -0400 > Chris Turner <[EMAIL PROTECTED]> wrote: > > > This leads me to ask - have you ever tried playing a guitar through > the DragonFly or FreeBSD sound system because it seems to me that the > video recording A/V sync problem is about as demanding ? >
I have not - part of the problem is that a lot of these apps are fairly Linux/ALSA centric due to the (percieved?) needs of the above, so things aren't yet compiling cleanly on DF - kind of a chicken and egg thing that I'm chipping away at over time. I suppose the standard answer from that perspective is that these are still two separate types of scenarios - the TV card / audio record synch is a passive, 'recording centric' type of thing that can be buffered more before to catch all the hardware interrupts (e.g 1 second is ok), whereas the music production case involves needing to hear things as they happen in "real time" (TM) so that the input (i.e. the sound resulting from a live performance) is "musically" in synch with the output of other, possibly pre-recorded data (e.g. < ~10msec of buffering/delay). So real-time monitoring latency is the key here due to the human interaction component. With the smaller buffering / stricter monitoring requirements, scheduling deadlines become more of an issue as dropouts start to occur, which is also possibly 'less acceptable' in the 'professional' case (this is very use-case-dependent), and things may or may not be compounded by heavy data processing, etc. (e.g. playing / mixing 10 tracks from disk through 12 plugins while recording 5 tracks and synthesizing 3 more kind of a thing) >From the research / discussions on the LAD list, it seems like the 'consumer' OS's (Windows, MacOS "classic", OS-X) have some kind of special scheduler hooks or API's for these kinds of scenarios (DirectSound, CoreAudio, etc) and that this is a 'hard problem' (TM) But perhaps with the faster speed / multi core setups that are becoming more common, these issues are starting to become less of an issue though. In any case, good point - I need to try it once I can get things to build - just trying to point out the various needs of different user communities w/r/t these API's.
