[linux-audio-dev] XAP and these <MEEP> timestamps...

[Paul Davis]

>> 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.

>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. we could be playing something at half-speed, for example,
or scrubbing using an MTC/MMC/SMPTE power jog wheel.

>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.

>> 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.

--p