Aspect ratio help needed

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Aspect ratio help needed

Postby Knightfire » Fri Jun 08, 2007 2:20 am

So I'm in the middle of correcting the aspect ratio of my recent video and I have ran in to a sort of brick wall. Put it shortly, I don't know what Aspect ratio I should put my footage in. Following VicBond007's guide, I should put it at 720 wide with 540 tall including the black bars. Another user on the site Said Elfen Lied (The anime I used for my video) should be at a ratio of 848x480. So I made screen caps of the same frame done at two different ratios.

Here's the screencap at 720x540

Here's the screencap at 848x540

What I need to know is:

1) For the 848 width, what is the correct vertical including blackbars?

2)which is the prefered spect ratio, in your opinion?

Thanks in advance.
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Postby BasharOfTheAges » Fri Jun 08, 2007 2:50 am

From a quick glance it seems the 720x540 looks correct and the 848x540 would be the same AR if you cropped off the black and did the actual image at that resolution - i'm no expert though, and since i'm at work i don't even have the tools to check any of that out =/
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Postby Knightfire » Fri Jun 08, 2007 3:10 am

I'll just stick with 720 then. Thank you for your time.
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Postby CrackTheSky » Fri Jun 08, 2007 3:26 am

Visually, the 848x540 looks better to me :/
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Postby Purge » Fri Jun 08, 2007 3:27 am

your getting aspect "ratio" confused with resolution.
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Postby Knightfire » Fri Jun 08, 2007 3:50 am

I've been up for 17 hours, 7 of them at work. Cut me a little slack xD
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Postby JaddziaDax » Fri Jun 08, 2007 6:39 am

the 720 looks right to me
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Postby Minion » Fri Jun 08, 2007 7:26 am

720x540 is the correct size.

i'd crop off the boarders, and make it 768x432 though
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Postby Keeper of Hellfire » Fri Jun 08, 2007 11:14 am

Yes, crop the black borders and resize it to any valid 16:9. Besides 768x432 you could make it 848x480 or 720x400 (it's your 720x540 sample without black borders). Black borders waste filesize and aren't good for compression.
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Postby Qyot27 » Fri Jun 08, 2007 11:39 am

On the DVDs, Elfen Lied is stored as 720x480 with an anamorphic flag (I'm assuming these are either the American or Japanese discs; hopefully the European release is anamorphic as well, if there is a European release?) - thus, just stretch the width from 720 to 848 and leave it alone, or resize proportionally from 848x480 to a smaller resolution and add black borders (or just leave it alone).

For instance, 640x352 (this one isn't exactly 16:9 but it would be the proper resolution for encoding hard letterboxing for DVD since the image itself and both of the borders would be multiples of 16).

However, if you are dealing with an MPEG-1 or MPEG-2 file, then there isn't any reencoding necessary to correct the issue. Demux the streams with TMPGEnc, get ahold of a program called ReStream, and run the .m1v (or .m2v, whichever you have) through it, specifying it to have a 16:9 flag. Then remux the fixed video stream with the audio stream and voila. I always use ReStream to make things anamorphic since I don't trust TMPGEnc to do it correctly - not to mention it's easier to figure out; I could never get TMPGEnc's settings right during the encode.
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Postby Qyot27 » Fri Jun 08, 2007 11:42 am

Qyot27 wrote:However, if you are dealing with an MPEG-1 or MPEG-2 file, then there isn't any reencoding necessary to correct the issue. Demux the streams with TMPGEnc, get ahold of a program called ReStream, and run the .m1v (or .m2v, whichever you have) through it, specifying it to have a 16:9 flag. Then remux the fixed video stream with the audio stream and voila. I always use ReStream to make things anamorphic since I don't trust TMPGEnc to do it correctly - not to mention it's easier to figure out; I could never get TMPGEnc's settings right during the encode.

I knew I should have checked better. ReStream only officially supports MPEG-2. I think there is a similar program for MPEG-1, though.
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Postby post-it » Fri Jun 08, 2007 5:09 pm

Qyot27 wrote:On the DVDs, Elfen Lied is stored as 720x480 with an anamorphic flag ... 16:9 but it would be the proper resolution for encoding hard letterboxing for DVD since the image itself and both of the borders would be multiples of 16) ...

umm, just out of curiousity ( and please correct me if/when I'm wrong here ) I thought Mpeg's were sized by 8's ... not 16's --- I believe ErMaC said something about that years ago ....
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Postby Scintilla » Fri Jun 08, 2007 5:24 pm

post-it wrote:
Qyot27 wrote:On the DVDs, Elfen Lied is stored as 720x480 with an anamorphic flag ... 16:9 but it would be the proper resolution for encoding hard letterboxing for DVD since the image itself and both of the borders would be multiples of 16) ...

umm, just out of curiousity ( and please correct me if/when I'm wrong here ) I thought Mpeg's were sized by 8's ... not 16's --- I believe ErMaC said something about that years ago ....

Each macroblock is 8 pixels by 8 pixels, but you're forgetting that one pixel in the chroma channels is equivalent to 4 pixels in the luma channel. So, an 8x8 macroblock in U or V = 16x16 macroblock in Y.

That's why it's much better for compression if letterboxing is a multiple of 16 pixels tall.
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Postby post-it » Fri Jun 08, 2007 10:42 pm

^_^
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Postby Zero1 » Sat Jun 09, 2007 7:39 am

Macroblocks in standards MPEG-4 Visual and older tend to use 16x16 pixel macroblocks. It's the DCT which works with 8x8.

Newer standards like H.264 use 4x4, 8x8, 16x16 and combinations of those, yet it is still good practice to use mod 16 because it still has 16x16 pixel macroblocks.
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