Re: [LAD] interesting blog post about syncing blender and ardour

Fons Adriaensen wrote:
> Locating (while stopped) is a remote control function, which
> is not the same as syncing. SMPTE in itself does not support
> anything similar to a locate command, it's not a remote control
> protocol but just an audio signal that can be decoded to time.
>
> SMPTE was developed as a way to sync audio (on magnetic tape)
> to optical film, and later to video. It was also used to sync
> audio tape machines, e.g. two 24-tracks recorders, to each other.
> In all cases the essential trick was to record it on tape as an
> audio track, thereby creating a time reference that was physically
> bound to the real audio tracks on the same tape. Sort of 'soft'
> sprocket holes, with the extra that each such hole also was also
> labeled with its number.
>
> Most machines supporting SMPTE sync would also support locating,
> by combining conventional mechanical tape motion sensing with
> the timecode system, and in the sense that when the master started
> rolling the slaves would chase to approximately the same location,
> then start rolling, then sync accurately. This latter could take
> some seconds, but once sync was established it could be very
> accurate, actually better than a sample at 48 Khz.
>
> Ciao,

For decades it was used to sync several VTRs by a computers cut list, to
cut videos and I guess it's still not outdated. Yes, it's very accurate
(IIRC the precursor of SMPTE was invented for the NASA Apollo missions).
I guess a noticeable pre-roll only will occur when tape recorders need
to reach speed, but I don't think noticeable pre-roll is needed for hard
disks. The big exception for a long delay is film cut, when several
machines have immense offsets because of cuts and the machines need to wind.

Ralf
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Received on Tue Sep 22 04:15:03 2009