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Re: More on 24 fps



In a message dated 97-05-22 20:33:42 EDT, Ron Martin wrote:

<< The 625 process strips off the "3" out of the 3/2 sequence leaving us with
a true 24 frame path that is recorded at the offspeed rate on our DVR-2000's.
 When played back at 25 fps we now have a deliverable product.  >>

What you're describing here is practically identical to the DEFT (Digital
Electronic Film Transfer) process promoted by Snell & Wilcox about five years
ago.  The only differences are that DEFT works at standard resolutions, not
HDTV, and is used to make very high quality NTSC-to-PAL conversions from
film-originated material.  How are you using the DVR-2000's?  Do you have
those special Sony data compression boxes they were talking about, so that a
HDTV bitstream can be recorded by a DVR-2k series D-1 machine?  If so, how
would you rate their performance?

<<The audio for all this is sample rate converted for the appropriate 525 and
625 masters so we don't deal with the large pitch correction issues.>>

Wait a minute!  Sample rate conversion doesn't change or correct audio pitch;
it only makes one digital audio sample rate into another, so equipment that
works at one sample rate can be fed otherwise incompatible signals having
various other sample rates.  In a DVTR, the audio output sample rate is fixed
by the tape speed, so anytime offspeed recording or playback is done on a
DVTR (outside the audio lock range "window"), sample rate conversion becomes
essential, **and** pitch correction is generally necessary as well.  The
running time difference between an equal number of film frames viewed on
525/60 and 625/50 systems remains the same, so please update me if there is
something else going on here.  Otherwise, I'd have to differ; the audio pitch
correction issues ought to be very much alive and well.

Christopher Bacon
DuArt Film & Video

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