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Old 22nd July 2007, 11:40   #1  |  Link
mjr4077au
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MeGUI: Should I "Resize to mod16" or "Overcrop to achieve mod16"?

As the title says, Should I "Resize to mod16" or "Overcrop to achieve mod16"?

What's the better way to do it? it would only be for PC playback so I don't care about compliancy with Standalones.
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Old 22nd July 2007, 17:09   #2  |  Link
saint-francis
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This is a question that I have struggled with myself. If you crop then you might loose a significant (to some people) portion of the movie. If you resize you may distort the picture. I personally resize and I have yet to encounter distortion that is so great that I am frustrated by it or even really notice it. But that's just me. There are some interesting threads on this in the DVD authoring sections you might want to check out.
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Old 22nd July 2007, 18:34   #3  |  Link
nurbs
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There shouldn't be any noticable distortion since it is an anamorphic encode with the correct DAR set. Personally I use "encode non-mod16". Some guys on the german doom9 board did a test and the loss of PSNR with that option was insignificant.
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Old 22nd July 2007, 18:40   #4  |  Link
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Do you ever run into compatibility problems with players or any playback issues at all from encoding non mod 16?
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Old 22nd July 2007, 19:36   #5  |  Link
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till is mod2 is ok.. but the encoder work better (in performance and quality) if video is mod16

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Old 22nd July 2007, 21:58   #6  |  Link
nurbs
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Quote:
Originally Posted by saint-francis View Post
Do you ever run into compatibility problems with players or any playback issues at all from encoding non mod 16?
PC plays it. PS3 plays it. That's all I care about. Since even Sony can make this work it shouldn't be a problem for other companies.
I don't own any portables to try it on, but I suspect bitrate and resolution would be the main problems with my encodes. I don't know if Quicktime and AppleTV can do non mod16 but then again they already choke on 3 b-frames, b-pyramid, ...

I don't think that either performance or quality suffer much. IIRC if you crop non mod16 the encoder pads the video to the next higher mod16 resolution with whatever has the best compressibility. So you waste a bit of bitrate and you have the same performance as if you would resize (up) to mod16.

In this thread on the german board they did some tests with crf encodes and while I am aware that it isn't the optimum method for such a test the bitrate for the non mod16 encodes is only ~0,5% higher and I wouldn't care about that.

Keep in mind that resizing also costs some quality.

Last edited by nurbs; 22nd July 2007 at 22:14.
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Old 23rd July 2007, 10:55   #7  |  Link
mjr4077au
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What I was referring to was that if I rip a 1.78:1 PAL Anamorphic movie, it'll come out as 1024x576 if I resize to mod16. I haven't tried a 2.35:1 film yet.

The thing is, since it's encoding at 720x576, the bits per pixel ratio is only 0.145 or something vs 0.230 if I cropped it which worries me but I guess the video at 0.145 looks OK and its basically if I had it fullscreen on my monitor already.
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Old 23rd July 2007, 11:03   #8  |  Link
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Quote:
Originally Posted by mjr4077au View Post
What I was referring to was that if I rip a 1.78:1 PAL Anamorphic movie, it'll come out as 1024x576 if I resize to mod16. I haven't tried a 2.35:1 film yet.
This is an incorrect assumption. The video is 720x576. Assuming there is nothing to crop, the video will come out at 720x576. You can set a playback flag in the container that will display it with the correct DAR.
Encoding to 1024x576 is bad for two reasons:
o You are upscaling. Upscaling is just a waste of bits.
o You are going to be resizing twice (once on encode, once on playback) (assuming your screen doesn't have a native resolution of 1024x). Compared to one resize on playback and a small resize to mod16 resolution, this is not optimal.
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Old 23rd July 2007, 12:35   #9  |  Link
mjr4077au
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You are right, I worded that wrong. I know it encodes the video physically at 720x576 and just resizes it. What I was referring to is that when I resize to achieve mod16 in MeGUI, It's stretching the video to 1024x576 which is over the size of a PAL DVD. Whether that is bad or not is anyone's guess, I suppose it's not alot different to making it fullscreen and thus, stretching it.

But basically what I should have asked straight up is, since it's encoding the video at 720x576, there are alot more bits than say, 720x400. That makes the bits per pixel less as there is more information to encode as the frame size isnt reduced. Will that have a adverse affect on the video. Simply, If I encode a video ad 720x576 and flag it for 1.78:1 and just encode at 720x400 (which would have a higher bits per pixel ratio), would it look any better or worse than each other. I probably should just rip a chapter of something and see for myself.
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Old 23rd July 2007, 13:57   #10  |  Link
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The resolution debate is old: do you use a higher resolution with lower bpp or the opposite?

There are a few things to remember:
o Video bitrate requirements are highly source dependant. I recently encoded a DVD full of music videos with --crf and had output filesizes from 400kb to 3000kbit. All you can use bpp for is this: "output quality is correlated with bpp". Don't try to derive any sort of number from it
o most people on these forums are aiming for quality as a primary goal. If this is your case the most appropriate thing to do is to avoid downsizing and encode at native resolution, with whatever filesize is appropriate. Here is the reason I highly recommend you use x264's 'Constant Quality' (ie --crf) encoding mode, which lets you specify a quality and have unknown filesize, rather than the other way around you are probably used to encoding with.
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Old 23rd July 2007, 14:06   #11  |  Link
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I just realised your from WA, Man we had some nasty storms in NSW here.

Back on topic, I do like good quality but I also like predictability. I think I will just resize to mod16. I ripped Requiem for a Dream, PAL, Resize to mod16, 448Kbps AC3 Audio, 1.36GB. The quality was pretty perfect, Maybe slightly less than DVD but I wasn't aiming for DVD quality. I may have 2,500GB of space, But I do like to conserve where I can as I rip music, game ISO's and/or MDF - stuff beyond the scope of doom9.

I thankyou all for your answers, I guess my question is answered - resize to mod16. Cheers, Mitch.
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