On Sunday 15 December 2002 13.32, Paul Davis wrote: > >> synchronizing position with a VCR via SMPTE (for example) has > >> nothing to do with sample clock sync. likewise, a word clock > >> connection between two digital devices has nothing to positional > >> synchronization. > > > >Good point. One could say that every sync source generates one of > >these: > > * timing data (tempo, sample clock,...) > > * positional data (song position, SMPTE,...) > > yes, but only one.
Yep. > >Positional data sort of implies that you can extract timing data > > as well, provided you get a stream of positional data with > > sufficiently accurate timing. > > no, you can't. how rapidly we are moving through a series of events > on a timeline has nothing to do with how many samples per second we > expect to process. Who said anything about samples/second? > we could be playing something at half-speed, for > example, or scrubbing using an MTC/MMC/SMPTE power jog wheel. Sure, that's exactly what I'm thinking about. You're suggesting that you *must* wait for each positional "event" before you do anything at all? What I'm talking about is just what every reasonably well written sequencer does when you tell it to lock to something. > >Anyway, in that other post, I think I said there *is* a relation > >between all of these, but I forgot to explain why: > > > > * Audio device syncs to wordclock > > * Sequencer uses audio for timing (nominal sample rate assumed) > > > >Note that both are just *sync* - not lock. If you wanted to sync > > with a VRC, you would most probably be using SMPTE instead of > > wordclock - and then, it would make a *lot* more sense to sync + > > lock the sequencer to that, and just let the audio interface do > > 48 kHz, or whatever you like. > > see above. you're confusing two entirely separate types of > synchronization. Confusing what with what? You can't sync a sequencer to a VCR, and let the audio interface (for the softsynths, or whatever) run at a fixed sample rate? Seems to work really rather well if the "audio interface" is built into an external MIDI synth, that doesn't sync or lock to anything it all... > >> so, slaving to a positional reference has no effect on sample > >> rate. > > > >Well, it *could*, if you assumu that one SMPTE frame corresponds > > to N samples... ;-) > > but you can't assume that. see above. Well, sorry about the bad joke... //David Olofson - Programmer, Composer, Open Source Advocate .- The Return of Audiality! --------------------------------. | Free/Open Source Audio Engine for use in Games or Studio. | | RT and off-line synth. Scripting. Sample accurate timing. | `---------------------------> http://olofson.net/audiality -' --- http://olofson.net --- http://www.reologica.se ---
