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64 lines
1.5 KiB
Text
64 lines
1.5 KiB
Text
1) playing DVD on 4:3 screen
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PAL DVD:
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- video size in pixels: 720x576
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- intended physical aspect ratio: 4/3
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- pixel aspect ratio: 16/15
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normal 4:3 computer screen:
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- screen size in pixels: 1024x768
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- physical aspect ratio: 4/3
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- pixel aspect ratio: 1/1
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-> scale to video size 720 . 16 / 576 . 15 = 11520 / 8640 = 144 / 108
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= 4 / 3
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2) playing PAL DVD on PAL TV
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PAL DVD:
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- video size in pixels: 720x576
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- pixel aspect ratio: 16/15
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=> intended display aspect ratio: 4/3
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w/h = DAR/PAR (with w and h of pixel video size)
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DirectFB PAL TV output:
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- screen size in pixels: 720x576
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- pixel aspect ratio: 16/15
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=> display aspect ratio: 4/3
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(v = video, source material - d = display)
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DARv = DARd <=> wv / hv * PARv = wd / hd * PARd
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<=> wd / hd = wv / hv * (PARv / PARd)
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no scaling necessary
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4) playing an NTSC vob on PAL TV
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NTSC VOB (4/3):
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- video size: 720x480
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- pixel aspect ratio: 8/9
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=> intended DAR: DAR = 720/480 * 8/9 = 80 / 60 = 4 /3
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wd / hd = wv / hv * PARv / PARd
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= 720/480 * 8/9 / (16/15)
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= 720 * 8 * 15 / (480 * 9 * 16)
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= 120 * 1 * 5 / (80 * 3 * 2)
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= 15 / 12
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= 5 / 4
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--> 720 x ( 720 * 4 / 5) = 720 x 576
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5) other examples
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- 720 x 480, 32/27 on a square display
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-> intended DAR: DAR = 720/480 * 32/27 = 80/3 * 1/15 = 16/9
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keeping w constant:
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720/h * 1/1 = 16/9 -> h = 720/16 * 9 = 45 * 9 = 405
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keeping h constant:
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w/480 * 1/1 = 16/9 -> w = 480 * 16 / 9 = 160 / 3 * 16 = 853.33
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