24P HD Framerate revisited.
Charles Tomaras
shoots? I seem to have missed the gist of it and was asked "what, why, where
and when" by someone and did not have the answers.
Why is this needed? What is the exact "slower" frame rate needed? How does
that relate to TC in the post production process. What can you do with
existing TC audio equipment that doesn't have that "slower" frame rate. Any
other info?
Thanks,
Charles Tomaras
Seattle, WA USA
Wolf
John Gilman wrote:
> My understanding of the whole thing. Others may add, correct, or whatever
>
> Because of the necessity of having NTSC downconversions available while
> shooting with the 24P HD camera, the whole thing needs to run at 23.976 fps
> (the standard .1% lower speed that corresponds with the 29.97 fps frame
> rate of NTSC video) instead of 24 fps exactly. The number is being rounded
> for notational convenience to 23.98. As a result, the 24 fps time code that
> is being used with this system is also running at a 23.98 frame rate. In a
> double system, film style shoot, this necessitates that the time code on
> the sound recording be one of two framerates. Either matching at 23.98 or
> standard 29.97. There are conversion boxes available that will convert
> between 23.98 and 29.97 time code, keeping the HH:MM:SS the same and
> correcting the frames appropriately. These are expensive and clumsy, but
> apparently they do work. Both Denecke and Ambient are producing time code
> generators that will create and deal with 23.98 fps T/C. If the double
> system sound is being recorded on DAT, it is my understanding that, at this
> point, 23.98 time code won't work and conversion is necessary. That may
> change if anyone modifies a timecode DAT, but I don't believe it's happened
> yet. With some machines, it's possible to shoot pulled up at 24 fps and
> have the result come back at 23.98. (The StellaDAT for one). The problem is
> that the sound will also be pulled down and will come back out of sync.
> It's necessary, in order for this to work, that the 23.98 fps time code be
> created without any pull-up or pull-down, since the final product is
> actually coming back at the 23.98 speed. Since the sound on the 24P is 20
> bit, 48kHz digital, most people seem to be treating the videotape sound as
> the primary recording and the double system DAT or other as a secondary or
> backup. In this situation, it's probably not a problem to use converted
> 29.97 fps timecode on the DAT since it may never actually be used. At this
> point in time, I think it's safe to say that the whole thing hasn't totally
> been worked out, but the system is working, one way or another.
>
> --
> John Gilman
> zou...@newscene.com
--
Wolf Seeberg
new email address:
wol...@mediaone.net
not necessarily what you see in the header
Mike Hall
> John Gilman wrote:
>
> . In a
> > double system, film style shoot, this necessitates that the time code on
> > the sound recording be one of two framerates. Either matching at 23.98 or
> > standard 29.97. There are conversion boxes available that will convert
> > between 23.98 and 29.97 time code, keeping the HH:MM:SS the same and
> > correcting the frames appropriately. These are expensive and clumsy, but
> > apparently they do work.
Charles Tomaras wrote:
> > >Why is this needed? What is the exact "slower" frame rate needed? How does
> > >that relate to TC in the post production process. What can you do with
> > >existing TC audio equipment that doesn't have that "slower" frame rate. Any
> > >other info?
I spoke yesterday to a mixer about to start a shoot where he will interface with a
24p digital camera. After tests at Panavision using a variety of recorders he
said that a Denecke SB-2 syncbox jammed with 23.976 from the camera will convert
the tc to 29.97 that can be jammed to a Fostex PD4 or HHB PDR1000tc (or fed as an
external source). When the video is digitized into the Avid and the recorder (HHB)
is in chase mode, the sync is fast and flawless.
Frankly, he lost me during the technical explanation ('0' frames synching up etc.),
but he was clear that the SB-2 will convert 23.976 to 29.97 and that the DAT
recorded with that time-code will synch up in post.
That seem like good news to me, although I await further reports confirming his
statements.
Mike Hall
>
>