sync, ltc, blackburst, wordclock.....

[huub]

Hiiii all,
I'm having a problem understanding what's exactly happening in the world of sync...
This week I recorded a concert on a pyramix system, I recorded in broadcast wave (time stamped)..
I put in normal ltc (smpte time code), provided wordclock wich is coming from our trucks master sync generator, wich also generates the video sync..
The pyramix system normally needs a blackburst video sync input, but for some reason the bb signal was unreliable, thus I let the pyramix use its internal sync..
now my question: The audio is synched from wordclock, the system is getting timecode, WHY does the system need video ref, what does it actually do with that? I know bwf files actually only write tc at the beginning of a file, and need constant synching when playing back, as to not drift, but my wordclock is already coming from the same generator as the video, that should be enough right?
Can someone enlight me??????
please?

[tenor39]

The system needs Blackburst to derive the correct digital sampling frequency. Video actually pulls the normal 48K down by a tiny bit, so there is a chance the audio will be slightly fast if not locked to the BB signal.

[gsilbers]

here u go

http://www.soundonsound.com/sos/Apr0...alclocking.asp

[huub]

ah, yes, the sos piece is quite clear.
And if I understand it correctly, indeed it is not necessary to have the video ref,
as my wordclock is already correct, coming from our video mastersync generator...