The C.A.S. and Digidesign Present
 

The Cinema Audio Society and Digidesign Present:
"Avid Insider - File Based Audio Workflows" Seminar

Here is a link to the Cinema Audio Society page that will give you
all the information to download the seminar. Here is the link:
http://www.cinemaaudiosociety.org/se.../workflow2.php

Also there is a link for an MP3 audio of the seminar.
A Podcast will follow shortly.

I would like to thank Digidesign and especially Scott Wood
for making this possible.
Happy downloads!

Re: The C.A.S. and Digidesign Present
 

thanks Scott & Marti!

GREAT! for those of us not in the LA area!!

look forward to seeing/hearing it!

tom hambleton, C.A.S.

Re: The C.A.S. and Digidesign Present
 

Yes Marti thanks for the seminar, and thanks to digi for the demo on DigiDelivery as well.

Re: The C.A.S. and Digidesign Present
 

Well Done Digi and Thanks marti!
I'm going to play it on our dub stage for my interns to watch and a couple of sound designers here in NYC.

cheers
geo

Re: The C.A.S. and Digidesign Present
 

Fantastic!

Re: The C.A.S. and Digidesign Present
 

This'll be a great reference. I was there, but what a lot of info to retain! Thanks Marti for the link.

Have they announced anything about the next one?

Re: The C.A.S. and Digidesign Present
 

Yes, thanks again for the wonderful link. These are the kinds of things I personally lie awake at night pondering...usually the one or two nights a year before I shoot a filmed furniture retailer spot using one of my clients' aged PD-2...I wonder about the signal path at the transfer house that pulls down our 48K 30fps DAT tapes on their way to 29.97 48k digibeta...analog for sure in my neck of the woods... And if I shot 30fps 48.048k instead, would it be easier for the transfer house to maintain an all-digital audio signal path... This seminar certainly gets it all straight in my head, and reinforces the concept that good communications between all involved is perhaps the most powerful tool at our collective disposal. And it's refreshing to be in the (virtual) presence of folks who ponder all of this a lot more often than one or two nights a year!

But there is one bit of minutia I have completely lost sight of over the years — I used to know the answer but the details have left me: exactly why did 29.97fps need to come about? I know 30 fps somehow clashes with our 60hz mains power...but what are the actual nuts and bolts of all that (it all came about in my lifetime, but as it was unfolding, I was more interested in making a good crystal radio). And how long does anyone think the 29.97/23.976 bump in the road will remain. With current technology, would it not be a simple mater to just have both film and TV run at 24fps — and be done with all of this SRC and pull up/down and drop frame and needless excursions from and back to the digital domain? We'd all have to buy new TVs but the world would be a better place, I guess...

Please excuse both my ignorance and my attempt at humor within such an esteemed thread.

Re: The C.A.S. and Digidesign Present
 

hi don,

when video was developed in the 1920's, the first TV's used phosphers. these were not fast enough to handle 30 FULL frames per second, so the engineers decided to tie the 60 FILEDS per sec to the AC cycles. but this was for B&W. when color television was being developed, engineers looked into how to make the new NTSC system backwards compatible with the old monochrome system. they thought by adding the color information on a sub-carrier, they could transmit both sugnals and still use the old radio transmitting technology. but this color signal would interfere with the audio subcarrier. so, it was decided to solve this by fractionally adjusting the frame rate of NTSC television from precisely 30 frames per second (60 interlaced fields per second) to approximately 29.97 frames per second (approximately 59.94 interlaced fields per second).

just another example of an engineering solution that makes things practically very over-complicated.

Re: The C.A.S. and Digidesign Present
 

To elaborate on the interference...

The argument when color was developed was that the frequency of the color subcarrier would create beating with the sound subcarrier that would be visible on some black and white television sets. The sound carrier, however, is frequency modulated. Therefore, beating would have only occurred at a specific frequency. A GE engineer determined that if the frame rate was dropped by .1% (from 30 to 29.97), that the beating would be reduced, and compatibility would be maintained (Lehrman 220). As a result of this change, 60Hz AC cannot leak into a video signal, or “bars appear to roll through the picture every 17 seconds” (Schubin 29).

The equation that has driven audio and video engineers mad by creating this non-whole number for video sync is:
[(number of scanning lines per frame•frames per second)/2]•455=color subcarrier frequency (Schubin 29). When the appropriate numbers are inserted, it becomes:
[(525•29.97)/2]•455 --> (15,734.25/2)•455 --> 7,867.125•455 --> 3,579,542
The NTSC adopted this equation, and could not change the lines per frame (or all TV sets would be obsolete), so they changed the frame rate. The idea behind the number 455 is frequency interleaving of the video and color signals, which would minimize interference between brightness and color data. The number 455 produces a result that is an even number of half the line rate (Schubin 29).

Now who can tell me why CD-quality audio is sampled at 44.1kHz (hint - its related)?

Sources:

Lehrman, Paul D. “SMPTE-ed Off--Why We Can’t Drop Drop-Frame.” MIX
Aug. 2001: 20-22, 218-222.
Schubin, Mark. “A Page of History.” Videography Apr. 1993: 29.

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