why 29.97?

[J. Baker]

I never realy thought about it before but why 29.97 fps and why not just go with 30 fps?

[vitualis]

Somebody can probably give a more technical answer but it was originally designed for 30 fps (for NTSC) but they needed a little bit more bandwidth for the colour... and they got it by dropping the framerate slightly.

Regards.

[canadateck]

I think they needed to slow it down to broadcast the color information in the film/Video when they went from Black&White to Color.



vitualis: beat me to it.

[edDV]

Back in 1954, 30 fps NTSC field tests caused monochrome TV sets to have harmonics show up in the video and an especially nasty buzz in TV audio.

A video genius calculated that reducing frame rate to 29.97 (15,734.26KHz horizontal scan frequency) and using 3.57945 MHz for color subcarrier, the harmonic interference fell outside the decoding range of an existing monochrome TV.

[Noahtuck]

Well look at the big brain on edDV

Watched Pulp Fiction the other night and jewels said it when he was eating a kahuna burger and asked about the quarter pounder in europe, and the kid answered and jewels said, "look at the big brain on brad here" And it popped into my head

[edDV]

Google will make your brain look big.

OK Google, I want royalties on that.

[Steve Stepoway]

The precise slowdown is 1000/1001. Another useless bit ok knowledge clogging up my brain cells.

[EddyH]

It's 999/1000 isn't it?

/pedantic



as in 29.97, divided by 3, = 9.99 exact

[Wilbert]

No, it's exactly 1000/1001 (this 29.97 is only an approximation).

[vhelp]

I never realy thought about it before but why 29.97 fps and
why not just go with 30 fps?

If your point of reference was w/ respect to (Film to TV) then this
*may* be on account of the Telecine process from 24 fps to to 30 fps,
but what I am missing here, (I forget why) is why 24 is 23.976 fps,
then after Telecine, its 29.970 fps. I thought I read it here, or
at doom9 back some time ago. (I just don't have enough brain cells
to give the answer, as I had to do a brain dump) Anyways.

Good question though

-vhelp 3264

[Sulik]

3:2 pulldown creates 5 fields from 2 progressive frames (2 fields).

30 = 24*5/4
29.97 = 30000 / 1001
23.976 = 24000 / 1001

[ebenton]

Because 29.96 was too slow and 29.98 was too fast. For something...whatever.

[lenti_75]

good question....WHY ?????

[garryheather]

Because us Brits wanted royalties on the PAL system...

[edDV]

Because us Brits wanted royalties on the PAL system...

PAL system came way after this NTSC fiasco, almost a decade later and it was the Germans not the Brits that came up with PAL. They had 10 years to observe progress in the USA.

Hey, I'm half Brit so I can tell the truth :P


This chart shows BBC was expreimenting with 405 line NTSC 1956-1964. Also 625 line NTSC 1964-67. I never knew that.
http://www.sptv.demon.co.uk/tvstandards.html

[EddyH]

No, it's exactly 1000/1001 (this 29.97 is only an approximation).

so thats why my NTSC <--> PAL soundtrack conversions ALWAYS drifted out by a frame or two over the course of a film, no matter what I did!

that'll help me alter my CoolEdit maths in future then (i've got a few foreign discs to do house-version converts on soon... i totally forgot my TV is only PAL60 not NTSC compatible, and the DVD player only does a bodge convert to PAL50 rather than the fully fledged thing)

This chart shows BBC was expreimenting with 405 line NTSC 1956-1964. Also 625 line NTSC 1964-67

Yeah, and we thought it was too rubbish so went with the more local PAL instead, even though it needed more complicated electronics... good call!
The black and white UK broadcasts were 405 (425?) lines for donkeys years in fact, up til about 1983 there was a seperate low-def service still running in addition to the 625 "high" def colour / BW compatible one. I think it might still be running in ireland?? (My handheld TV with a UHF/VHF switch used to pick up *something* black and white for a couple hours every night coming across the irish sea, when i lived in north wales..)


edit - looked over that table you linked.... some very wierd stuff in there! For starters..... what's a "line frequency divider"? (all those 3x3x3x13s and so on).... field sequential colour, did that involve the 1940s equivalent of a half-meg frame buffer to hold each frame, or did it do a very flickery job of drawing a full red, then full green, full blue frame "live"? Bizzare. And it looked like the UK authorities standardised on a "283 and a bit" horizontal colour frequency early on, as they kept it from NTSC into PAL... the explanation for that choice would be interesting to say the least... (283.7 currently, over the airwaves, it claims - must be why the colours clash at such a relaxed rate on weather announcers ties and why it was hard to tell the difference between a monitor/SCART and RF signal with old computers... interestingly its very close to one third of the 848 pixels my DVD software wants to play all widescreen discs at... coincidence?)

and would germany's original 441 line service be anything to do with the current, puzzling 44100Hz sampling rate for CDs? (not just 100x the frequency, but it's scanning rate was 11025Hz, and presumably its sound bandwidth would be similar)

[dcsos]

NTSC = "National Television Standards Committee"
or
"Never Twice the Same Color"

PAL= "Phase Alternate by Line"
or
"Palace Approved Look"

SECAM= "Sequential ?????
and here's where my knowledge and ability to make funnies...breaks down...


perhaps the TV stadards are metaphors for the POLITICS of the adopting
country?

[edDV]

I always heard it this way

NTSC - Never Twice the Same Color

SECAM - Something Essentially Contrary to the American Method

PAL - Peace At Last

[edDV]

The black and white UK broadcasts were 405 (425?) lines for donkeys years in fact, up til about 1983 there was a seperate low-def service still running in addition to the 625 "high" def colour / BW compatible one. I think it might still be running in ireland?? (My handheld TV with a UHF/VHF switch used to pick up *something* black and white for a couple hours every night coming across the irish sea, when i lived in north wales..)

Over here in the USA, we are doing what the Brits did in the 67-80s. We have the new 480p, 720p, 1080i. etc. digital DTV service running in parallel to the old 525 line NTSC service. Congress wants to cut the old service in urban areas next year but are afraid it will affect elections.They want to sell rights to the urban VHF spectrum for mobile use.

edit - looked over that table you linked.... some very wierd stuff in there! For starters..... what's a "line frequency divider"? (all those 3x3x3x13s and so on).... field sequential colour, did that involve the 1940s equivalent of a half-meg frame buffer to hold each frame, or did it do a very flickery job of drawing a full red, then full green, full blue frame "live"? Bizzare. And it looked like the UK authorities standardised on a "283 and a bit" horizontal colour frequency early on, as they kept it from NTSC into PAL... the explanation for that choice would be interesting to say the least... (283.7 currently, over the airwaves, it claims - must be why the colours clash at such a relaxed rate on weather announcers ties and why it was hard to tell the difference between a monitor/SCART and RF signal with old computers... interestingly its very close to one third of the 848 pixels my DVD software wants to play all widescreen discs at... coincidence?)

beats me.

and would germany's original 441 line service be anything to do with the current, puzzling 44100Hz sampling rate for CDs? (not just 100x the frequency, but it's scanning rate was 11025Hz, and presumably its sound bandwidth would be similar)

I seriously doubt a link exists.

[EddyH]

lol ok

just a little too deep for a saturday night really

[garryheather]

Because us Brits wanted royalties on the PAL system...

PAL system came way after this NTSC fiasco, almost a decade later and it was the Germans not the Brits that came up with PAL. They had 10 years to observe progress in the USA.

Hey, I'm half Brit so I can tell the truth :P


This chart shows BBC was expreimenting with 405 line NTSC 1956-1964. Also 625 line NTSC 1964-67. I never knew that.
http://www.sptv.demon.co.uk/tvstandards.html

I'm 100% Brit and it's called humour, lighten up !