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11th July 2005, 14:13 | #1121 | Link | |
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Quote:
I think it would make more sense if it read something like... "Custom PAR" and not "Sample Aspect Ratio": - Cheers
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11th July 2005, 14:37 | #1122 | Link |
Mr. Sandman
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Custom PAR is misleading.
I modified it and it's "Sample AR" now...
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11th July 2005, 14:49 | #1123 | Link |
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SAR is pixel aspect ratio, no?
why not simply call it "Pixel AR" than?
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11th July 2005, 15:02 | #1125 | Link |
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you guys make me cry can't you just come up with a unique and precise name for every single thing, nooo you have to make life diffcult.
here is my proposition, let's erase all text in the gui's so that no one knows what option does what, obscure but FUN FUN FUN!! you never know what you gonna get
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11th July 2005, 16:14 | #1126 | Link |
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Aspect Ratio Naming
And here was me thinking this sort of thing had been agreed ages ago
3ivx has been using the terms PAR (for Pixel Aspect Ratio) and DAR (for Display Aspect Ratio) for ages. XviD has also been using the term "Pixel Aspect Ratio" for ages - And the term "Picture Aspect Ratio" to describe the Display Aspect Ratio... but lets not go there! In my opinion the term PAR (Pixel Aspect Ratio) is all we need because PAR offers the greatest flexibility when it comes to altering the shape of your encodes. Including the possibility of generating encodes to either, PAL 4:3 / 16:9 DAR or NTSC 4:3 / 16:9 DAR That said, an incorrectly shaped encode with PAR signalling can be a bit of a pain to sort out "after the event".... Which is why I feel we could really do with an tool such as MPEG4 Modifier which x264 friendly.... but that's for another thread! Cheers
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11th July 2005, 17:00 | #1127 | Link | |
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Quote:
i personally definitely wouldnt think of "pixel" when i read "sample"
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Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora | Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free |
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11th July 2005, 17:26 | #1128 | Link |
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Actually, i still think 'sample' is the most appropriate term. 'Sample' refers the smallest / undivisable unit of the signal, so it can't refer to the frame. And 'pixel' refers to what is shown on the screen ( meaning, after scaling ), so it would be inappropriate in that case. But that's bitching on the definition... ( /me thinks the mpeg4 guys spent at least a week in meetings just to decide that name )
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11th July 2005, 17:28 | #1129 | Link | |
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SCNR. bis besser, Tobias P.S.: It would be too easy if we would understand each other right away, right?
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11th July 2005, 18:21 | #1131 | Link |
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As far as I'm aware SAR (Storage Aspect Ratio) refers to the pixel aspect ratio of the source as it stored digitally on electronic media, before correction...
In the case of DVD, a PAL 720x576 source, has a SAR of 1.25:1. And an NTSC 720x480 source, has a SAR of 1.50:1 Cheers
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Last edited by SeeMoreDigital; 12th July 2005 at 07:28. |
11th July 2005, 19:16 | #1133 | Link |
German doom9/Gleitz SuMo
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May depend on how exact you calculate: 702:{768|1024} or 704:{768|1024}. But such cancelled fractions shall be suitable as long as the differences between the ITU specs and the calculated fractions are below recognition...
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11th July 2005, 21:33 | #1134 | Link | |
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Quote:
PAL 720x576 (4:3) has a DAR of 16:15 PAL 720x576 (16:9) has a DAR of 64:45 NTSC 720x480 (4:3) has a DAR of 8:9 NTSC 720x480 (16:9) has a DAR of 32:27 Cheers
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11th July 2005, 21:36 | #1135 | Link |
German doom9/Gleitz SuMo
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@ SMD:
No. 4:3 video has a DAR of 4:3, 16:9 video has a DAR of 16:9 (DAR = "Display ASpect Ratio" is the whole picture, after resizing: width:height). At least it is documented this way in the MPEG-2 specification ISO/IEC 13838 Part 2 in chapter 6.3.3. MPEG-2 video with aspect ratio flags "DAR 4:3" or "DAR 16:9" have to be resized so that the ratio between the width and the height of the decoded frame has to become 4:3 or 16:9. Last edited by LigH; 11th July 2005 at 21:38. |
11th July 2005, 21:54 | #1136 | Link | |
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In the case of say, an PAL 16:9 anamorphic DVD...
An 720x576 (1:1) source image without correction = SAR An 720x576 with 64:45 PAR correction = DAR EDIT: Or as SteveG put it.......... Quote:
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Last edited by SeeMoreDigital; 11th July 2005 at 22:03. |
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11th July 2005, 22:31 | #1138 | Link |
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Okay think of SAR x PAR = DAR this way...
An SAR of 1.25 (ie: 720x576) x an PAR of 1.0666666 (ie: 16:15) = an DAR of 1.3333333 (aka 4:3) An SAR of 1.25 (ie: 720x576) x an PAR of 1.4222222 (ie: 64:45) = an DAR of 1.7777777 (aka 16:9) An SAR of 1.50 (ie: 720x480) x an PAR of 0.8888888 (ie: 8:9) = an DAR of 1.3333333 (aka 4:3) An SAR of 1.50 (ie: 720x480) x an PAR of 1.1851851 (ie: 32:27) = an DAR of 1.7777777 (aka 16:9) Cheers
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11th July 2005, 22:48 | #1139 | Link |
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@SeeMoreDigital,
You are both right, but the problem is the naming of things. The MPEG-2 specs (page 47) says the following SAR = DAR * horizontal_size/vertical_size with horizontal_size the width of the displayable part of the luma component of pictures in samples (vertical_size idem ...). I think this just means the number of horizontal pixels. So, what they call 'horizontal_size/vertical_size' is called 'storage aspect ratio' by Stegre. What they call SAR (or sample aspect ratio) is called '1 / PAR' by Stegre. So, for example SAR = DAR * horizontal_size/vertical_size = 3/4 * 720/576 = 0.9375 Interestingly, the MPEG-2 doesn't mention PAR at all. So, a question for Manao, where is the term PAR coming from (if it isn't mentioned in any specs)? edit: i didn't know the DAR values in the MPEG-2 specs are actually 3/4, 9/16, etc ... Last edited by Wilbert; 14th July 2005 at 16:36. |
11th July 2005, 22:57 | #1140 | Link | |
German doom9/Gleitz SuMo
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Quote:
pel_aspect_ratio -- This is a four-bit integer defined in the following table. pel_aspect_ratio - height/width - example 0000 - forbidden 0001 - 1.0000 - VGA etc. 0010 - 0.6735 0011 - 0.7031 - 16:9, 625line 0100 - 0.7615 0101 - 0.8055 0110 - 0.8437 - 16:9, 525line 0111 - 0.8935 1000 - 0.9375 - CCIR601, 625line 1001 - 0.9815 1010 - 1.0255 1011 - 1.0695 1100 - 1.1250 - CCIR601, 525line 1101 - 1.1575 1110 - 1.2015 1111 - reserved __ Unfortunately, I do not yet know where to find MPEG-4 specifications... |
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