Subject: Re: [linux-audio-dev] XAP and these
On Sunday 15 December 2002 13.32, Paul Davis wrote:
Yep.
> >Positional data sort of implies that you can extract timing data
Who said anything about samples/second?
> we could be playing something at half-speed, for
Sure, that's exactly what I'm thinking about. You're suggesting that
What I'm talking about is just what every reasonably well written
> >Anyway, in that other post, I think I said there *is* a relation
Confusing what with what? You can't sync a sequencer to a VCR, and
> >> so, slaving to a positional reference has no effect on sample
Well, sorry about the bad joke...
//David Olofson - Programmer, Composer, Open Source Advocate
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: Sun Dec 15 2002 - 20:43:20 EET
From: David Olofson (david_AT_olofson.net)
Date: Sun Dec 15 2002 - 20:38:47 EET
> >> 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.
> > 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.
> example, or scrubbing using an MTC/MMC/SMPTE power jog wheel.
you *must* wait for each positional "event" before you do anything at
all?
sequencer does when you tell it to lock to something.
> >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.
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...
> >> rate.
> >
> >Well, it *could*, if you assumu that one SMPTE frame corresponds
> > to N samples... ;-)
>
> but you can't assume that. see above.
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