Resizing up Will Enhance Video Artifacts?

[J-Wo]

I know it's a cardinal rule in encoding that's it's always better to resize DOWN than to resize UP when encoding, and I believe this is especially true for AVIs. something about how resizing up will enhance artifacts and such.

The AVIs I encode are sometimes in a resolution of say, 608x320 or 640x272 or 624x352. I often have a hard time deciding which resolution to encode at, either 704x480 or 544x480. For years I've always chosen the latter but then I realized that if I chose 704x480 with resize overscan of 3, then I would actually be encoding closer to the original resolution (with just some AddBorders to fill out the screen size). For example, a 624x352 source would be resized to 656x332. So while I am shrinking the image vertically (good) I am also stretching it horizontally (bad). For the same source, if I were to encode at 544x480 with resize overscan of 2, the image would be resized to 512x352. So I keep the same vertical res but shrink the horizontal considerably. Given these choices which would be the better for picture quality?

[bigggt]

HI J-Wo

I don't have an answer for you but i would also love to know the answer,I too am so confused on which resolution to pick,most of my files are 600 and above but like you said alot of people say to never use a higher resolution(Phil )

BUt what i don't like is if i use 544x480 it will play on 2 of my dvd's but not all and them,and down the road if the dvd players stop working then i have to go through the headache of finding one that will play the resoultion

SO the obvious step is to go to 352x480 but then i feel like i'm loosing out on quality

[J-Wo]

see for me 352x480 is NOT an obvious solution. You are losing almost HALF of your vertical resolution (i.e. half as wide)! I usually compromise and use 544x480 because both my players can play it, but as you noted not all players like this resolution (like my brothers) so I can't share those discs with others).

I'm beginning to think 704x480 isn't so bad an option, so long as you play around with resize/overlap overscan in moviestacker and take a look at how much (or rather little) of the original image is cropped and/or resized.

I do hope others (perhaps more informed) people can provide us with more input!

[kwag]

Quote:

Originally Posted by J-Wo

I'm beginning to think 704x480 isn't so bad an option, so long as you play around with resize/overlap overscan in moviestacker

Exactly
I usually do ALL my KVCDs at 704x480, unless my short prediction sampler looks bad, and then my second choice is 528x480.
If it still doesn't look good (my targets are 99% of the time for once CD) at that resolution, then I encode 704x480 for 2 CDs.
I have yet to encounter a single movie that I can't encode on 2 CDs, with almost perfect results

-kwag

[J-Wo]

I found an old thread in this forum where incredible and dialhot have a mini discussion on this issue:
http://www.kvcd.net/forum/viewtopic....ghlight=resize

In it, Incredible says basically this (edited for grammer)

Quote:

Its better to upscale the width than the height!
Most of the sharpness is preserved by maintaining the height of a movie.

In moviestacker, set the cropping method to accurate and ensure that the the Resize height value does NOT change from the Film pixel height value.

edit: Kwag, why on earth are you still encoding kvcds? Get yourself a DVD burner!!!

[J-Wo]

okay so here's my question. I have a film that is 608x320. Is it better to resize to 656x320 or 512x320? The first is for a destination resolution of 704x480 (resize overscan 3) and the second is for 544x480 (resize overscan 2). I am, of course, encoding for KDVD.

[Dialhot]

For me there is not even a possible discussion : do you know TV sets that have an overscan area of 24 pixels ? Yes ? Then send them to a tech, it need to be fixed !

24 pixels x 2 = 48 pixels, that is 10% of the height and 7% of the width of your flat "active zone"

[J-Wo]

I guess you're telling me that overscan 3 is never a good option? The thing to keep in mind is this is a 1.78:1 widescreen avi and my destination is 4:3 letterboxed. This means there is only 24 pixels overscan on the left and right. Surprisingly, both my tv sets (one standard, the other hd) can show that perfectly without seeing any black bars on the sides!

So to rephrase my question... is it better to upsize the width or downsize it? I believe this means I am talking about vertical resolution (although I admit I get these things mixed up all the time)

[Boulder]

My 4:3 TV has an overscan of little over 24 pixels on the left and right side. On top and bottom it's somewhere between 16 and 24. I've seen some movies in which the border has been almost as wide as the overscan area on my TV (checked with VDub), which means that if I had a 16-pel overscan, I could see the border quite easily

[Dialhot]

Quote:

Originally Posted by J-Wo

So to rephrase my question... is it better to upsize the width or downsize it? I believe this means I am talking about vertical resolution (although I admit I get these things mixed up all the time)

If I were you, I would use the lower res. But let your eyes decides because all depend on the quality of your TV set.

[incredible]

Quote:

Originally Posted by J-Wo

I guess you're telling me that overscan 3 is never a good option?

Resizings will be done by FitCD and Moviestacker using a temporal desqueezing to PAR 1:1 "WITHIN" its calculations. Often the result is the more you add overscan, the more the orig image will be cropped in its orig movie area

So a little rule is that the main purpose of compression using an adding of black overscan area is given by MOD16. 8 or 24 do give some compression but do not follow the main purpose.

"why?"

Because MPEG encodings are based on 8x8 DCT Block algorhythms.

"So why MOD8 isnt enough?? or 24 as its devidable by 8???"

Because we do encode in YV12 colorspace, means the HALF of horizontal and HALF of vertical color!!! frequency. So a MOD8 scaling/Letterboxing would do its purpose on luma 8x8 DCT matching but NOT on chroma. The chroma grid on that scale/letterbox matrix would end up effectively in 4x4! Means no "real" Gain as we want to.

On 16x16 we got 2 8x8 luma DCT blocks and 1 8x8 chroma DCT Block = Compression purpose of 8x8 when scaling/letterboxing is preserved.

[kwag]

Quote:

Originally Posted by J-Wo

edit: Kwag, why on earth are you still encoding kvcds? Get yourself a DVD burner!!!

I do have a DVD burner
But some movies still look excelent on one CD, and it's far cheaper than DVD media
Also, KVCDs are more challenging to do, because of smaller resources
Copying a DVD (DVDShrink, etc.) takes the fun out of that
But I do use my DVD burner for KDVDs, but only when I want to put at least 3 or 4 full length movies on one DVD

-kwag