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problems with calculating correct aspect ration
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Scree
Newbie
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20. August 2005 @ 08:45 |
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I didn't know where else to post this, so here's my problem:
I have an Avi with the size of 608x320 px and every pixel is film information (no borders).
I want to turn this into an anamorphic NTSC DVD (so it displays correctly on 16:9 TV sets) with a 720x480 res. Since the source is non anamorphic I can't figure out how much I should stretch the hight. (if I wanted 4:3 I would've resized it to 720 times roughly 405 and added in black borders but then the movie would appear squished on a 16:9 TV unless I use the TV's built in zoom feature, and I hate to use it)
Maybe someone here can point me into the right direction?
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Minion
AfterDawn Addict
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21. August 2005 @ 12:36 |
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Well my Calculations tell me that to resize this File to 16:9 animorphic you would resize it to 704+304 and Fill the Rest of the 720+480 with Borders....
You can also try 704+400(4:3) or 704+368(1:1).....
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Scree
Newbie
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22. August 2005 @ 15:23 |
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Thanks for the reply (although the numbers I used in the end were quite a bit different.)
I resized the film to 720x450 and added 15 pixels worth of borders on both top and bottom. Looks perfekt now on both 4:3 and 16:9 displays. (I can't really remember how I came up with the numbers thuogh)
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celtic_d
AfterDawn Addict
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22. August 2005 @ 18:42 |
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Yep, 450 is about right if you are using the full 720 width, 448 would probably make more sense though.
Don't know where Minion's numbers come from though. No way that the anomorphic version should have less vertical resolution.
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Scree
Newbie
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22. August 2005 @ 20:32 |
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448 might make more sense but then who's gonna notice the difference in the end?
(if I were to convert the AVI again I'd probably just blow it up to the entire height of 480 - not a big difference between a 1.9:1 and a 1.778:1 ratio)
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celtic_d
AfterDawn Addict
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22. August 2005 @ 23:41 |
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That was my point. You aren't likely to notice the difference, but the encoder will and since 448 is divisible by 16 it should compress better, potentially offering better quality for the same filesize.
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Minion
AfterDawn Addict
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23. August 2005 @ 11:36 |
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I got my Calculations useing the Aspect Ratio/Resolution Calculator in Gordain Knot....These Calculations are useing Pixel Aspect Ratio because all AVI Files use a Pixel Aspect Ratio of 1:1 (Accept DV) so I find I get better results If I calculate the PAR on a 1:1 Basis....
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celtic_d
AfterDawn Addict
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23. August 2005 @ 19:15 |
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Not all avi's are 1:1 and as far as I know DVD's never are.
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Minion
AfterDawn Addict
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24. August 2005 @ 10:57 |
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DVD"s aren"t AVI...I"m Talking about PAR not DAR and all Standard Microsoft AVI"s Have Square Pixels which means they are 1:1...
AVI files do not have an Aspect ratio Flag , aspect ratio Flags are Purely a Property of Mpeg Files...It is the Aspect ratio Flag that tells your DVD player how to Display the Video as Mpeg files are displayed useing there Pixel aspect ratio not there Resolution ,The Resolution is only used so the DVD player Knows How many Pixels to Display and these Pixels are Displayed useing there Aspect ratio....
Cheers
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celtic_d
AfterDawn Addict
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24. August 2005 @ 18:22 |
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MPEG4 streams can have non 1:1 PAR's, this can be read no matter what container they are in, including AVI.
Also, with Open-DML avi's you can specify an output resolution, which amounts to the same thing.
I was talking about PAR.
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Minion
AfterDawn Addict
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24. August 2005 @ 19:00 |
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Here is a Quote from "VideoHelp.com" (Formerly VCDHelp.com and DVD-Rhelp.com) regarding this Subject....
Quote:
Formats using aspect ratios:
All AVI formats currently display 'as is'. In other words, they don't support aspect ratio's. Whatever their width and height are, defines their aspect ratio. When converting to AVI, you should always ensure the AVI's width and height, conform to it's intended display aspect ratio. MPEG, on the other hand, has an 'aspect' tag (call DAR), that tells the MPEG player what display aspect ratio the mpeg is using. This tag, or property, basically says 'this mpeg should be this wide, based on it's height, and your display's (TV's) aspect ratio'. It affects a lot for a little tag . Because of this property, we can resize your MPEG's physical width to any size supported by the media it's placed on. The HEIGHT of the MPEG, combined with the Display Aspect Ratio (DAR) tag, can then be used to stretch your MPEG back to it's proper playback or display width on playback. Just remember that AVI doesn't support aspect ratios, while MPEG does.
Here is a link to the whole Explanation....
http://www.videohelp.com/forum/userguides/174200.php
Cheers
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This message has been edited since posting. Last time this message was edited on 24. August 2005 @ 19:02
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celtic_d
AfterDawn Addict
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24. August 2005 @ 22:41 |
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Scree
Newbie
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25. August 2005 @ 07:19 |
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Well, seeing that the aspect ratio I went with looks pretty much perfect on my TV I guess my (and Celtic_d's) calculations were right. The result is all the proof I need here.
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Minion
AfterDawn Addict
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25. August 2005 @ 11:25 |
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Well your Link didn"t Say anything I allready didn"t Say...I was Talking about "Direct Show Microsoft AVI" not "Open DML" (like DV AVI) which I allready stated does support Aspect ratio"s.....
You are Arguing "Open DML" and I am Arguing "Direct Show"....
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