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 -'
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