We've all had to deal with the ramifications of the National Television Standards Committee's decisions to design the then new color television standard for backward compatibility with the existing monochrome system. As a result, the North America and Japan have been saddled with an arcane standard for both television and time code. Fortunately, DTV is on the horizon. Read on and weep...
The "0.1 percent" issue is how film and video post houses in this day and age of digital deal with the temporal discrepancy between the slower realm created in NTSC color video and real-world time, which runs 0.1 percent faster. If you've ever dealt with 29.97 vs. 30, 59.94 vs. 60, 44.056 vs. 44.1, 47.952 vs. 48, pull-down vs. pull-up, varispeed, or sync wide vs. sync narrow, then you've delved head first into this dilemma.
The annoyance (or benefit, depending on your point of view) has long been considered the technical cornerstone of film post production houses in the digital era; yet the popular but somewhat disconcerting and unorganized trial-and-error approach in dealing with this issue, though feasible and often times circumstantially necessary, seems rather unprofessional - especially since we, the film post industry, make claims such as "the best in the business," "years of experience and expertise," and "dedicated to improving the way we do post."

TRANSPARENT DILEMMA
Apparently, the handful of individuals who truly understand the "0.1 percent" issue as it pertains to audio are mostly design engineers who unfortunately lack the experience of motion picture sound work; and those in the editorial houses whose job it is to effectively keep this dilemma transparent are mainly efficient end users who, though readily familiar with the operations of every piece of gear in the facility, lack a design engineer's specialized approach to functionality. Is it so necessary for the post community to have such a firm grasp of this concept? Technical reasons aside, of course we should! Owners and managers often forget that the most beneficial and lasting methods of permanently improving and uniquely defining a facility is moderating ignorance! Hey, knowledge is FREE! Now although plenty of infamous 0.1 percent issues seem to have the film post industry mind-boggled, one caveat in particular is detailed in this article. 
It's taken some time but the eclectic film post industry, which understandably is always dead last against other audio venues in the race to play catch-up to technology, is now finally aware that a speed difference exists between video and "real-world" time in film, and I'd say a third of us can now effectively - though uncomfortably - deal with the annoying prospect that color video runs at 29.97 fps (sort of) vs. a true 3O fps. 
However, with everything in post becoming more and more sophisticated and with the deluge of software upgrades cluttering our workspace with more complicated and confusing options, and with the surge in audio/video synchronization problems among desktop editing workstations, I think it's time to reveal that color video does NOT run at 29.97 fps! Uh, say again? Well, theoretically NTSC color video runs slightly faster than 29.97 fps, but instead of printing 29.97002616431? fps all the time, the pioneers in the industry reasonably decided to make things easier to read and use the truncated 29.97 value instead.
Thus in the past several years, with the merging of technologies and the blending of music and post, this industry (which doesn't concern itself with hard core techno-engineering stuff) has gotten used to seeing "29.97" splattered all over the place - from trade magazines to users manuals; and along with the technology this misconception has rapidly bloomed. Now, when an inexperienced engineer fresh out of the University of Silicon Valley Whiz-Kids, or a head technoid at a post facility comes along and has to do some sort of calculation or designing with these numbers, the results will inevitably be incorrect: 30 to 29.97, yeah that's 1,000 to 999-29.97 is 0.1 percent less than 30, no problem, right? Well, mathematically speaking yes, but for audio post, not so. Here's a real-world example:

LET'S PRETEND
Don T. Know, the director of a music video, shoots on location in film with the lead singer of No Money lip-synching to a seven minute song played back wild on a consumer DAT player. Don gets his footage telecined to video and heads over to the local film post house where the $4,000-per-week sound editor, Les Clue, is supervising the project.
Les gives his $1,400-per-week assistant sound editor, Mimi Butkiss, the responsibility of resolving the speed of the DAT. When Les isn't looking, Mimi passes the task onto the less-than-minimum-wage intern Alec Smart, fresh graduate of the Recording Engineering program from the Yew C. Less Institute of Music Technology. Alec has read that video runs at 29.97, so if he varispeeds this wild DAT down 0.1 percent on their DA6O, then 30 - (30 x 0.1 percent) = 29.97 - that's it! Pleased with his ingenuity, Alec glows warmly with the knowledge and pride that he's done such great work for No Money. Bad tongue-and-cheek aside, Alec made a mistake. Because we now have accuracy of up to 1:48,000th of a second (and even 1:96,000th in some cases) and an unwieldy 44.1 k sampling rate, precision takes on an entirely new role. Fortunately, AES and SMPTE endorsed a method for synchronizing digital audio with picture, a 1,001 to 1,000 ratio between true 30 fps and NTSC color video.
The problem with Alec's calculation is his incorrect assumption that for digital audio NTSC color video runs at a precise 29.97 fps. In the world of digital, NTSC color video, according to AES and SMPTE, runs at precisely:

(30 fps x 1000) / 1,001 =
29.97002997 fps

Translation: 30 fps is 0.1 percent faster than NTSC color video (as it pertains to digital audio), and although the number 29.97 is 0.1 percent less than 30, NTSC color video (again as it pertains to digital audio) does NOT run 0.1 percent slower than 30 fps! Did you get that?
Think about this: 999 is 0.1 percent less than 1,000, but 1,000 is NOT 0.1 percent greater than 999; 1,001 is 0.1 percent greater than 1,000, but 1,000 is NOT 0.1 percent less than 1,001. That's why it IS possible to use varispeed to increase the audio rate by 0.1 percent from the world of video to a real-world film speed, but NOT possible to varispeed a real-world program down to NTSC color video! So from this point on, be wary of anything labeled 0.999 or 29.97.

OTHER PROBLEMS
There are some other problems with Alec's scenario (besides the ethical). The technically savvy will realize that a consumes DAT's internal crystal typically rates between +50 to 100 ppm. For a seven-minute song, this results in a worst- case scenario of a loss or gain of about 1.25 frames, just noticeable for the scrutinizers.
However, even if we assume that a custom-modified DAT player with a tighter crystal tolerance was used for the shoot, Alec would still be using his facility TC DAT's internal oscillator - a crystal with no doubt a worse specification than the customized location DAT machine - because few TC DAT players allow the user to varispeed by 0.1 percent divisions while referenced to black burst.
Hence, the inaccuracy of the internal clocks here will contribute more significantly to drift than any miscalculation between 999:1,000 and 1,000:1,001 (the proper ratio) on Alec's part. (The crystal argument is that if internal oscillators get any more accurate, we wouldn't need house sync, just some sort of phase sync.) So what's the correct answer? Alec should have inserted 29.97 ND time code referenced to video on the DAT, and then played it back at 3O ND with the band nrr setting off. Another solution is to varispeed the DAT by +0.1 percent at the shoot, and in post turn varispeed off.The best solution is to use a TC DAT player referenced to the same 60 Hz as the camera (cameras don't run at precisely 24 fps either) at the production shoot. If the TC DAT was prestriped at 29.97 NDF, then the TC DAT player must have its band nrr setting turned off at the shoot; and once in post, the DA6O is left at 29.97 NDF referenced to video.
If the TC DAT was prestriped at 3O NDF (band nrr off) referenced to video, then that DAT player must be left at this setting through the entire production and post production process, with only its reference source changing. Use this same procedure if the TC DAT was prestriped at 30 NDF referenced to its internal clock; the only difference is that in the latter case the music sounds 1/1,001 times slower but with everything still in sync (try and figure that one out!).l know, I know, this 1,001:1,000 business is getting way too esoteric now, but I am aware of one misimplementation of this AES/SMPTE recommended practice (and suspect two) by a major DAW manufacturer commonly used in film post "Selective sacrifice," a.k.a. "corner-cutting," is what engineers and manufacturers necessarily must do to stay competitive - it's really shocking how certain cost cutting features are being designed (or misdesigned) for pure marketing reasons - and it's difficult, even for design engineers, to test for these practices on strictly an end-user level without any design notes or schematics.

YOU'D BETTER CONFORM
However, not conforming to a digital audio synchronization standard is a big no-no when it comes to post, so heads up everybody. Times are a changin'! It just isn't good enough for us in post to know or do only the "creative stuff" anymore, especially when artistry and technology have merged. (Actually there was always a one-to-one correlation between the two - look at Da Vinci.) What, you think solving the techno mumbo-jumbo puzzle isn't a creative process? Anyway, the important thing is not what you know, it's how you apply what you know. "Push-button" knowing is no big deal. Understanding is.

by Evan T. Chen

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Evan Chen is a free-lance all-around post production kinda guy in Los Angeles. He is currently negotiating with various companies to design a DAW specifically for post based on high end NT platforms. Feel free to contact him at:



evantchen@yahoo.com