Converting PAL-NTSC runtimes

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Converting PAL-NTSC runtimes

Postby Brent_Reid » 23 Sep 2017 14:06

Does anyone have a simple formula (or know of a website!) for converting runtimes from PAL-NTSC and vice versa?
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Re: Converting PAL-NTSC runtimes

Postby James-Masaki_Ryan » 24 Sep 2017 00:09

NTSC to PAL:
First convert the time to seconds. https://www.calculateme.com/Time/Seconds/ToMinutes.htm
For example 100 minutes = 6,000 seconds

a - (a x 0.04) = b

6,000 - (6,000 x 0.04) = 5,760

Reconvert the seconds to minutes with the above site. https://www.calculateme.com/Time/Seconds/ToMinutes.htm

100 minutes NTSC = 96 minutes PAL.

PAL to NTSC:
First convert the time to seconds. https://www.calculateme.com/Time/Seconds/ToMinutes.htm
For example 96 minutes = 5,760 seconds

a + (a / 24) = b
5,760 + (5,760 / 24) = 6,000

Reconvert the seconds to minutes with the above site. https://www.calculateme.com/Time/Seconds/ToMinutes.htm
96 minutes PAL = 100 minutes NTSC
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Re: Converting PAL-NTSC runtimes

Postby Brent_Reid » 24 Sep 2017 12:04

Fantastic answer, James - and ta v much; it's exactly what I was looking for! Have saved it to my favourites... :D
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Re: Converting PAL-NTSC runtimes

Postby James-Masaki_Ryan » 26 Sep 2017 05:53

No problem. Just simple math, it is. Surprised I could not find any of these formulas anywhere else and had to make them myself.
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Re: Converting PAL-NTSC runtimes

Postby Ulrich_Christensen » 05 Oct 2017 09:21

While James' answer is correct, I think I want to demystify the numbers a bit.

NTSC DVDs display at 24 frames per second, while PAL DVDs display at 25 frames per second.

So,

NTSC to PAL:
(NTSC runtime) x 24 / 25 = (PAL runtime)

PAL to NTSC:
(PAL runtime) x 25 / 24 = (NTSC runtime)


TRIVIA
Movies in the cinema run at a standardized frame rate of 24 fps (frames per second),
with exceptions for old silent movies which ran at crank speed (usually 14-26 fps)
and newer high framerate 48fps (HFR) which is only used on a handful of movies.
These exceptions do not apply to DVDs.


NTSC is natively ~30 fps (29.97fps) and a conversion from 24fps is done using a technique called Three-two pull down, which preserves the original framerate of 24fps by blending interlaced frames.

The infamous 4% PAL-speedup arrives as a result of the fraction 24/25 computing to 0.96. A slight pitch correction is applied to the audio to make it sound right.

DOWN THE RABBIT HOLE TRIVIA

The 30fps NTSC and 25fps PAL are actually a lie, since both NTSC and PAL display frames as two half-frames (odd lines and even lines respectively), called fields, interlaced (that is the "i" seen in newer standards).
NTSC display ~60 fields/second, while PAL displays 50 fields/second. Each field is taken at a separate time interval, which aids in the smoothness of motion, but can result in some jagged edges on fast movement if you do a freeze frame.

NTSC is 29.97fps (59.94 fields/second) instead of 30fps because of the introduction of a colour signal in 1953, which wasn't originally part of the standard in 1941 (it was monochrome). Adjustments were made for backward compatibility.
PAL was developed in 1962 as solution for problems with NTSC for the European market and had colour from the get-go.

The difference between framerates has to do with power frequency as adopted by different parts of the world (primarily America and Europe).
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Re: Converting PAL-NTSC runtimes

Postby Nigel_Badnell » 31 Oct 2017 22:24

The Prof.

"Long live the new flesh."
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Re: Converting PAL-NTSC runtimes

Postby Alister_Manson » 01 Nov 2017 09:33

NTSC runtime x0.96 = PAL runtime.

PAL runtime x 1.04 = NTSC runtime.
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Re: Converting PAL-NTSC runtimes

Postby Nigel_Badnell » 30 Nov 2017 23:09

PAL runtime x 1.04 = NTSC runtime.

As Ulrich stated above, it is 25/24=1.041666... (as many 6s as you like).

Using 1.04 is o.k. for rough comparisons, but if you are looking at small cuts of
a few seconds per 100 mins then 1.04167 is necessary.
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