Random Questions aka Deep Thoughts

cheroxy wrote on 5/6/2006, 2:16 PM
As I sit here and edit I have had a few random questions pop into my head:

-where does the default setting of 00:00:09:29 for lenght of generated media come from?

-when I do a build dynamic RAM preview, what are the setting for that render?

-why did tv originate at 29.97 fps instead of 30, or even 60 for that matter?

Thanks

Comments

farss wrote on 5/6/2006, 2:43 PM
1) It's in Options, same setting as for default still length
2) Project settings
3) Duh, it's NTSC so nothing makes any sense.

No seriously, something to do with multiples of the film rate which isn't exactly 24 fps either. Could be a bit off the mark but there's plenty about this on the web with enough maths to keep you occupied for a fair while.

And just in case you think those numbers don't need to be precise, trust me, they do. Just ask the poor soul who did a project with around 10,000 cuts and multiple PIPs in FCP and at the end found out he was five frames out and had to redo the whole thing.

Of course if he was using Vegas he could have just extended the audio 5 frames, should I email him that little gem of info?

Bob.
johnmeyer wrote on 5/6/2006, 2:51 PM
NTSC video WAS 30 fps until color was introduced. There are several excellent explanations on the web that describe all the gory technical detail, but in order to maintain compatibility with existing B&W sets (and there weren't many sets back in 1950 when this decision was made -- later formalized in 1953), the frame rate was adjusted slightly downward. Nobody much cared in the analog days of tuning knobs, but in the digital age, that 1000/10001 conversion is a real headache.
winrockpost wrote on 5/6/2006, 3:02 PM
Wow Cheroxy,, that must be one boring edit :)
Grazie wrote on 5/6/2006, 3:20 PM
Yeah, Rockie? And you read his post? . . oops, I just read yours . . u-huh!

How come the Text Sync Option is Greyed Out?

Grazie
Former user wrote on 5/6/2006, 6:08 PM
Originally NTSC TV was 30 frames per second. This was based on the electrical system being 60 cycles. (you might have heard of 60 cycle hum).. Since each frame is made up of 2 fields, this works out to 60 fields a second.

When color was introduced, the video signal had to be slowed down in order to insert the color information. This slow down resulted in 29.97~ fps.

Dave T2
rs170a wrote on 5/6/2006, 9:32 PM
...all the gory technical detail...

And if anyone really cares (which I highly doubt!!), here it is.

For historical accuracy, the previous horizontal scanning frequency was 15,750 Hz, and the vertical scanning frequency was 60 Hz.
When the NTSC color video system was introduced, a small change was
required in order to add the additional color information to the transmission signal. A color subcarrier was added, at 3.579545MHz, and the signal rates of all other portions of the video signal were then derived from this new subcarrier’s frequency. This newly defined relationship changed the horizontal and vertical scanning frequencies slightly. The new horizontal scanning frequency was defined as 2/455 times the subcarrier or 15,734.26Hz, while the vertical scanning frequency (field rate) was defined as 2/525 times the horizontal frequency, or 59.94Hz.

Mike
Serena wrote on 5/6/2006, 10:06 PM
Mike, that's nice to know, so thanks for setting it down.

Farss, now you're going to have to explain "film speed not precisely 24fps". I know about 24, 25, 30 and the special 29.97 (drop frame) for use with NTSC colour TV and I've just confirmed that in my American Cinematographers Handbook. Or is this a video film speed that is as close as it can get to 24fps?
apit34356 wrote on 5/6/2006, 10:55 PM
Serena, I think Farss was talking about the mech subsystems in film projectors.
Serena wrote on 5/7/2006, 1:27 AM
In that case, projectors run at 24 or 25 fps, professional machines being run by sync motors.
farss wrote on 5/7/2006, 4:43 AM
I think I was referring to the frame rate of film in NTSC video, I'd wrongly assumed the odd NTSC frame rate was derived from this however I now realise it must be the other way around. If the NTSC field rate is not precisely 60Hz then 24p has to be not exactly 24p i.e. 23.976 which is what Vegas runs 24p as.

Which probably explains why you cannot accurately use most NLEs to cut neg.

Which in turn leads one to ask how come Vegas doesn't have a true 24fps capability?

And does it even matter?

Bob.



JohnnyRoy wrote on 5/7/2006, 7:12 AM
> Which in turn leads one to ask how come Vegas doesn't have a true 24fps capability?

Who said it didn’t? Just set your project Frame Rate to the 24.000 (Film) setting.

~jr
cheroxy wrote on 5/7/2006, 9:32 AM
You guys are amazing!