Årets trend etter at "1080p-racet" har lagt seg er tydeligvis 24p. Sony, Samsung, Philips konkurerer om å tilby "ekte" 24p inngang som skal gi den ultimate kino-lignende opplevelsen for materiale som opprinnelig er filmet for kinosalen. Dessuten tilbys gjerne forskjellige forbedrende teknologier som skal nyttiggjøre seg et display som kan oppdateres 100/120ggr pr sekund ved å "gjette" seg fram til mellomliggende bilder som ikke eksisterer. Det er noe uenighet om dette siste forbedrer eller forverrer filmskaperens intensjon, og derfor kan man som regel velge å slå av funksjonen.
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It just seems strange (and stupid) that now after finishing the war of "TRUE 1080p HD", they have started focusing on the temporal aspects of video by introducing /24p and 120Hz panels, but they left out the possibility of showing 24p video as even-timed 24p/48p/72p/96p/120p. Especially with a source that is sampled at a critically low sampling frequency, I claim that there is good reason not to fiddle with the sampling times.
1) 50Hz ticks
2) 60Hz ticks
3)240Hz ticks
4) time [s]
5) Movie camera timings
6) Cinema projector timings (48fps)
7) "NTSC" 60i timings
8 ) "NTSC" 60p de-interlaced timings
9) "NTSC" 60p IVTC timings
10) These "bad" 24p->60p->120p display timings
11) Proper 24p->120p display timings
12) "PAL" 24p->50p display timings
FRC = Frame Rate Conversion (digital or mechanical changing the period between frames). Could be integral (eg 25p->50p) or non-integral (eg 24p->60p)
IVTC = Inverse Telecine: Recreating an original 24p sequence from a 50i/60i delivery
deInt = Deinterlacing: lines lost in an interlaced delivery
- Kode: Merk alt
Source:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
####|####|#####|##########|####|24p |24p |24p |24p |24p |24p |24p |
Delivery format:
####|####|#####|##########|####|reel|60i |60i |60i |60i |60i |50i |
Processing steps:
####|####|#####|##########|####|FRC | no |de- |IVTC|IVTC|IVTC|IVTC|
####|####|#####|##########|####| | |Int | |FRC |120 |50 |
####|####|#####|##########|####| | | | |60 | | |
####|####|#####|##########|####| | | | |FRC | | |
####|####|#####|##########|####| | | | |120 | | |
Physical display/capture rate:
####|####|#####|##########| 24 | 48 | 60 | 60 | 60 |120 |120 |50 |
Presentation/Capture timing:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
-------------------------------------------------------------------
0 | 0 | 0 | [0/1200]| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| | | [1/1200]| | | | | | | | |
| | | [2/1200]| | | | | | | | |
| | | [3/1200]| | | | | | | | |
| | | [4/1200]| | | | | | | | |
| | 1 | [5/1200]| | | | | | | | |
| | | [6/1200]| | | | | | | | |
| | | [7/1200]| | | | | | | | |
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| | 2 |[10/1200]| | | | | | 1 | 1 | |
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| | |[12/1200]| | | | | | | | |
| | |[13/1200]| | | | | | | | |
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| | 3 |[15/1200]| | | | | | | | |
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| | |[18/1200]| | | | | | | | |
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| 1 | 4 |[20/1200]| | | 1 | 1 | 1 | 1 | 1 | |
| | |[21/1200]| | | | | | | | |
| | |[22/1200]| | | | | | | | |
| | |[23/1200]| | | | | | | | |
1 | | |[24/1200]| | | | | | | | 1 |
| | 5 |[25/1200]| | 1 | | | | | | |
| | |[26/1200]| | | | | | | | |
| | |[27/1200]| | | | | | | | |
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| | 6 |[30/1200]| | | | | | 1 | 1 | |
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| | 7 |[35/1200]| | | | | | | | |
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| 2 | 8 |[40/1200]| | | 1 |1/2 | 1 | 1 | 1 | |
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| | 9 |[45/1200]| | | | | | | | |
| | |[46/1200]| | | | | | | | |
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2 | | |[48/1200]| | | | | | | | 2 |
| | |[49/1200]| | | | | | | | |
| | 10 |[50/1200]| 2 | 2 | | | | 1 | 2 | |
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| | 11 |[55/1200]| | | | | | | | |
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| 3 | 12 |[60/1200]| | | 2 | 2 | 2 | 2 | 2 | |
| | |[61/1200]| | | | | | | | |
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| | 13 |[65/1200]| | | | | | | | |
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| | 14 |[70/1200]| | | | | | 2 | 2 | |
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3 | | |[72/1200]| | | | | | | | 2 |
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| | 15 |[75/1200]| | 2 | | | | | | |
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| 4 | 16 |[80/1200]| | | 2 | 2 | 2 | 2 | 2 | |
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| | 17 |[85/1200]| | | | | | | | |
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| | 18 |[90/1200]| | | | | | 2 | 2 | |
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| | |[92/1200]| | | | | | | | |
| | |[93/1200]| | | | | | | | |
| | |[94/1200]| | | | | | | | |
| | 19 |[95/1200]| | | | | | | | |
4 | | |[96/1200]| | | | | | | | 3 |
| | |[97/1200]| | | | | | | | |
| | |[98/1200]| | | | | | | | |
| | |[99/1200]| | | | | | | | |
| 5 | 20 |[100/1200]|3 | 3 | 3 | 3 | 3 | 3 | 3 | |
...
Source:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
####|####|#####|##########|####|24p |24p |24p |24p |24p |24p |24p |
Delivery format:
####|####|#####|##########|####|reel|60i |60i |60i |60i |60i |50i |
Processing steps:
####|####|#####|##########|####|FRC | no |de- |IVTC|IVTC|IVTC|IVTC|
####|####|#####|##########|####| | |Int | |FRC |120 |50 |
####|####|#####|##########|####| | | | |60 | | |
####|####|#####|##########|####| | | | |FRC | | |
####|####|#####|##########|####| | | | |120 | | |
Physical display/capture rate:
####|####|#####|##########| 24 | 48 | 60 | 60 | 60 |120 |120 |50 |
Notes:
Note the difference between "proper" 24p->120p and the "improper" 24p->60p->120p at the 50/1200 timing (bold): The second FRC cannot know that sourceframe#2 is now the current source-frame since that information is concealed by the first FRC producing a seemingly valid frame equal to sourceframe#1 for that time.
The bad approach simply leaves with a 6:4 cadence @120fps that looks just like a 3:2 cadence @60fps for constantly lit (ie LCD) displays. One possible exception to this is if their motion-compensated FRC is able to smooth out some errors, but it is still a seemingliy totally unnecessary degradation.
The good approach gives us a 5:5 approach, a 120fps display that is as jerky as 24p ought to be, but not more. (This also depends on the display technology, a plasma screen or some other "flash"-based display will probably give a temporal perception close to that of a cinema projector for correct 5:5 120fps).
The PAL/50Hz column does not produce a cadence in sync with the (original) source, instead it is constantly shortening the frameperiod by ~24/25 resulting in a slightly shorter movie without the time-base artefacts that the US people have.
-k