discriminating between the NUMBER of frames and the NAMING of frames.
DF and NDF have the same number of frames in an hour.
Subcarrier and the rest have nothing to do with it. The number of
frames in black and white television from 50 years ago doesn't matter
to anyone. I know the history. I went to college and paid attention
and have read the history since then in various books. This thread was
built on the question of the actual realtime of drop and non drop of a
tv spot THIS WEEK, not in 1940.
On Oct 22, 2009, at 10:16 AM, Dennis Degan wrote:
>
> I sigh:
>
> Look Steve, there seems to be a disconnect between what I'm
> explaining
> and what you're hearing. I've already said it before (but you did not
> include it in your most recent message), but to reiterate in even more
> excruciating detail: The reason we have drop frame time code is
> because the FCC decided early in the 1950's that if we are to provide
> the public with a compatible color TV system, the relationship between
> the visual and aural carriers' frequencies must maintained at 4.5MHz.
> A choice of color subcarrier frequency had to be made so that the
> Intercarrier Frequency Offset is not changed, yet the color sidebands
> can be interleaved with the sidebands of the luminance information
> providing a minimum of interference with both the aural carrier and
> other channels in the band. To do this, the the horizontal line
> frequency was lowered to 15,736Hz from 15,750Hz, which lowered the
> frame rate slightly to 29.97fps. This allowed the color subcarrier
> frequency to interleave synchronously with the horizontal lines. That
> decision led to a choice of color subcarrier of 3.579545MHz; a
> frequency that would interleave with the new lower horizontal line
> frequency.
> Previously (in the years of television that preceded color TV), the
> old B&W TV system used sync generators that either locked their field
> rate to the AC power frequency (exactly 60Hz) or they generated their
> own crystal frequency standard (not locked to AC), also running at
> EXACTLY 60Hz. As everyone knows, there are 2 fields for each frame,
> therefore the old B&W frame rate WAS exactly 30fps. So there actually
> WAS a difference in the number of ACTUAL frames produced between the
> original B&W system and the new compatible color system. That
> difference was (and still is) 108 frame per hour.
> But the fact is, it doesn't matter if there ever was B&W TV running
> at
> exactly 30fps or not. The fact is, NTSC color TV runs at 29.97fps,
> which is 108 ACTUAL REAL frames LESS than the number of frames that
> WOULD fit into an hour if the frame rate actually WAS exactly 30fps.
> So if you number those NTSC frames in sequence as if there were 30
> frames in each second (which we know there are not), the time code
> that
> results will not follow clock time. This is NDF. So to correct for
> this frame-numbering error, there must be created a formula that skips
> numbers and brings the resulting time code into line with actual clock
> time. This is DF. Now, to further annoy and bore you all, let's go
> through Steve's points as he wrote them:
>
> On Oct 21, 2009, at 7:46 PM, Steve Hullfish wrote:
>
>> The confusing thing here is that there's really no such thing as
> 30fps except on the web. In NTSC it's ALWAYS 29.97.
>
> I answer:
>
> It may be confusing, but there IS (or WAS) such a thing as 30fps
> video. It WAS black & white video and was the ORIGINAL NTSC, NOT the
> color NTSC. The color NTSC was actually the SECOND NTSC. I never
> refer to the first NTSC because of the confusion. Therefore, I never
> said that 30fps video (real or imagined) is NTSC (although
> technically,
> it WAS NTSC; the FIRST NTSC. You want confusion? THAT's confusing).
>
> Steve:
>
>> I know there's such a thing as true 30fps, but this statement in your
> post, when describing drop vs. non-drop - which is what the thread is
> - about is deceiving:
>
>> "The difference in the total number of frames between 29.97fps NTSC
>> video and exact 30fps video is approximately 108 frames per hour"
>
> I answer:
>
> The original discussion was the question of DF, when you either start
> at :28 frames or :02, what frame number you'd end up with after
> exactly
> 30 seconds. Then Phillip Hodgetts offered his blog entry with a
> graphic that showed the difference between DF and NDF visually. I
> mentioned in his blog and in a follow up message here that there's
> more
> to the story. This is where the discussion went tangent. That was my
> fault and I apologize for that.
> Phillip has a real good understanding of DF and NDF TC. He stated in
> his blog this:
> "...it took three pieces of additional information before I truly
> understood it: Rainer Standke's insistence that "frame is a frame is a
> frame"; the realization (although known) that 29.97 is actually slower
> than 30 fps with the consequence that each frame runs slightly longer
> than at 30 fps; and that the correction can't be applied evenly."
> Also, please note that in Steve's quote of my message shown above, I
> say "EXACT 30fps", not approximate 30fps.
>
> Steve also said:
>
>> If, by "30fps video" you mean NDF timecoded NTSC video...
>
> I reply:
>
> No, I DON'T mean NDF timecoded NTSC (color) video. I meant what I
> said: 30fps video. I said "EXACT 30fps". 30 ACTUAL FRAMES PER
> SECOND.
> It's theoretical now, but existed before color NTSC TV. And it
> doesn't matter if it ever existed at all because it's just a way to
> divide an hour of actual clock time into a number of video frames as a
> reference. It's a fixed number of frames because it's a fixed amount
> of time at a specific frame rate.
>
> Steve:
>
>> That's why I said you were mathematically correct but semantically
> incorrect. An hour (as a unit of time) has an identical number of
> frames whether it's drop from or non-drop frame. It has 108 frames
> less
> than 30 (frames) times 60 (seconds) times 60 (minutes). If you mean
> real 30fps video, which is really not an acceptable form of video at
> all - unless you're Canon - then there are more frames in 30fps video,
> but the discussion is really about how 29.97 is named in terms of
> timecode. Bringing a different frame rate into it just confuses
> things,
> like saying "There are fewer frames in an hour of 24fps film than in
> an
> hour of 29.97 video." It just confuses the argument by measuring
> apples
> and oranges.
>
> I say:
>
> This is why I don't think you, Steve, got my point. On the above, we
> don't disagree. But that wasn't what I was talking about. Perhaps
> it's my fault for taking this discussion far beyond it's original
> query. For that, I apologize. And for that reason, I will have
> nothing more to say on it. As far as I'm concerned, it ends here.
>
> Dennis Degan, Video Editor-Consultant-Knowledge Bank
> NBC Today Show, New York
>
>
>
> ------------------------------------
>
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>
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>
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>
>
>
>
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