Fairuse wizard "Resolution/AR" question!

[UnD3R0aTh]

Hi,

..first off let me start by saying that I really appreciate the work you guyz are doing here, and the help your offering to the entire web, I downloaded so many tools from here, and I read so many guides on this site, really lots of useful stuff!

..anyway, let's move on to my question!

..I'm new to DVD ripping, i recently started to learn about DVD structure and how ripping works, and these technical terms like anamorphic and letterboxing ..etc etc but I find it much either to use Fairuse wizard than other programs like MeGUI, and even AGK when encoding xvid, though xvid is not the case here! but of course, I don't wanna do that at the expense of the quality of the files that I'm encoding!

..my first attempt at ripping a DVD with Fairuse, at "H264/ac3/very slow" preset, quite actually lived to my expectations, though it took way much more time than i expected , still the quality looks excellent, but after playing the DVD in mpc, and the encoded file in mpc and maxmizing to full screen, by comparing the two videos at the same frame, I noticed the AR of a person in my rip looks a tiny bit different from the AR of the DVD (his face looks fatter)

..and Gspot says AVI has AR of 1.79 and the VOB has AR of 1.77, so there is a difference in AR

p.s. I chose the resolution recommended by Fairuse which is 688x384, and I couldn't find any of the resolutions recommended by Gspot after analyzing the VOB

..so, what are these calculations based on? is there a program that can calculate the "perfect" resolution to maintain the same exact AR of the DVD? or is it always gonna be relatively close, so it won't be noticeable by the eye, but there's always gonna be a slight difference in numbers?


VOB:



AVI:



Edit:

..i'm using HB now, can't say it's better, but meh, that's what everybody says!

[jagabo]

h.264 codecs work best with frame sizes that are integer multiples of 16 (mod16). Programs often distort the AR slightly to conform to that requirement. So instead of resizing to 688x387 (a perfect 16:9 ratio) your software resized to 688x384.

[UnD3R0aTh]

thx for your reply, but that leaves so many of my questions unanswered! plz take the time to write a more elaborate answer when you have the chance! thx

[UnD3R0aTh]

ok, i get it now! the DVD i have, the horizontal dimension does not stretch, depending on the aspect ratio of the DVD whether it's 16:9 (1.778 which is not to be confused with flat widescreen which has AR of 1.85) or 4:3 (1.33), the vertical dimension either is gonna be squeezed in the former to 405 or stretched in the latter to 540, this is called letterboxing!

..now with the former, 405 will be rounded to 400, but the aspect error will be big (0.1), this is when fairuse or any other program with inherent calculating qualities comes handy sense it recommends the most suitable resolution with the smallest AR error, and that is 656x368, but with the latter, since it can not be stretched to more than 420, the horizontal dimension is gonna be squeezed to 640 which is the minimum squeeze amount that can be done to keep a full vertical dimension and maintain a perfect AR that is exactly identical to the DVD

..oh, and the reason why VOBs play with the correct AR, is becoz they still have the AR flag which tells the player to resize the frame correctly, you can see how really ugly they look if you go to MPC, right click it, go to video frame then uncheck "keep aspect ratio"!

any additions?

[jagabo]

Aspect ratio calculations:

https://forum.videohelp.com/threads/316284-What-is-the-mathematical-formula-to-figure-o...=1#post1957501

For example, for a 16:9 720x480 VOB file I picked, one of the sizes GSpot recommended was 574x315. Here's how it came up with that size:

The 16:9 picture in a 720x480 DVD is contained in the inner 704x480 pixels (there are 8 pixels of padding on each side, sometimes these contain picture, sometimes they are black bars). So the 720 pixel wide frame contains a picture slightly wider than 16:9. How much?

DAR = SAR * PAR
DAR = 720/480 * 40/33
DAR = 1.5 * 1.2121
DAR= 1.8181

I don't know exactly how GSpot decided 574 pixels was a good width (it's not, 576 would have been a better choice since it's mod 16) but here's how it got the 315 for the height:

DAR = SAR * PAR
1.8181 = 574/height * 1/1 (PAR is 1/1 because we're using square pixel encoding in the output video)
height = 574 / 1.8181
height ~= 315.7

[UnD3R0aTh]

..is cropping important? i read it only increases the size a tiny bit since the black bars are "black", and they're constant throughout the video! besides that, cropping always causes problems when resizing and picking AR

[jagabo]

Noiseless black bars don't consume much bitrate with high compression codecs. Noisy black bars do -- like from a VHS recording. You're looking at ~1 percent larger files in CRF or CQP mode, 1 percent less "quality" in bitrate mode. The other issue is DCT ringing artifacts that you can get at the boundary near the black border.