Why do you always have to resize...

... DivX or Xvid or any other codec whenever you watch to burn it to a DVD to watch on a TV? I have a DivX video that is 320 x 240, but viewing it on a TV results in cut off sides. It also is different with every TV you play it on (some tv's will cut off less than others). However, it always looks the same no matter which computer you play it on. 320 x 240 is a 4:3 ratio, and I believe my TV is too, why does it cut off stuff? And why don't store bought DVDs do the same thing? A store DVD will look and fit exactly the same on your tv as it would on your computer.

 

I had the same question, and this is the info I found:

Some people are real sticklers for getting perfect aspect ratio. But it's almost impossible to get a perfect aspect ratio when we’re limited to resizing by 16 pixel jumps every time. It makes cropping awkward and limits us to weird sizes.

AN ASPECT RATIO OF 4:3

If your movie has an aspect ratio of 4:3 then there's nothing to it! All PAL (European) DVD's use 720 x 576 pixels and all NTSC (North American) DVD's use 720 x 480 pixels. This means a perfect aspect ratio should be 1.33:1.

Because we must resize in blocks of 16 x 16 pixels, this makes following the closest sizes easier. Remember that the closer to 1.33:1 it is the more exact the aspect ratio to a 4:3 TV screen:

PAL/NTSC 720 x 576 / 720 x 480
(Size) (Ratio)


720 x 544 1.32:1
640 x 480 1.33:1
592 x 448 1.32:1
544 x 416 1.30:1
512 x 384 1.33:1
448 x 336 1.33:1
400 x 304 1.32:1
384 x 288 1.33:1
336 x 256 1:31:1
320 x 240 1.33:1


For Xvid, we recommend something like 640 x 480 or even 512 x 384. For PAL and for NTSC you can go as low as 336 x 256 since you're used to 20% less TV resolution than the rest of the world! Also, full DVD resolutions will very often cause jerky playback. This will happen each time the Xvid video hits a keyframe. For my 500 MHz CPU, the Xvid codec gives optimum smooth playback with under 1000 blocks of 16 x 16 pixels before problems. Therefore a full 720 x 576 resolution Xvid with 1620 blocks is no good. If you intend to make a Xvid video that will play on anyone's machine, then we suggest you consider the following:

ANAMORPHIC ASPECT RATIOS

Here’s where it gets tricky. First, many films say something like: 2.35:1 Anamorphic (Approx.). If you’ve read the article on Anamorphic films, you’ll know that they are at 720 x 576 (or 720 x 480) and will give a squashed picture.

The following information will be useful for getting correct aspect ratios:

STRETCHING 16:9 / 24:10

2.35:1 WideScreen is probably the most used Anamorphic size in Europe. But because we are limited to 16 x 16 blocks (because of the limitations of the MPEG format), the only size that is exactly 2.35:1 is 640 x 272 pixels. Actually, it’s an aspect ratio of 2.35294117647059:1 (if you really want to impress your friends).

These are some of the closest:

672 x 288 (2.33:1) (we don’t recommend encoding anything over 640 wide)

640 x 272 (2.35:1)

528 x 224 (2.36:1)

Now forget all that. If you just resize an Anamorphic film to 2.35:1 you'll see the incredible pancake show! This is because even Anamorphic DVDs are still recorded with black bars at the top and bottom of the image. DVDs only support 4:3 and 16:9 aspect ratios. In other words, they can be either 1.33:1 or 1.85:1. If another size is needed, like 2.35:1, then they’ll squish the picture on the DVD itself so that when it is resized to either 1.33:1 or 1.85:1 it will look the correct shape. This means the following sizes are the most common to use. The closer to a ratio of 1.85:1, the better.


PAL/NTSC 720 x 576 / 720 x 480
(Size) (Ratio)

720 x 384 1.87:1
640 x 336 1.87:1
576 x 304 1.89:1
512 x 272 1.88:1
480 x 256 1.87:1
448 x 240 1.86:1

Hope this helped a little.

 

I used NeroVision Express 2 to burn a latest DivX AVI onto DVD for watching on TV. While constructing the menu, I noticed there was a dotted rectangle approximately 20% smaller than the full frame labelled "safe zone". So I resized both my menu and my movie, but I was confused because my movie was perfectly 320 x 240. I had to reduce both values by 20% in order to get it to fit inside this "safe zone". Sure enough, it did play on the tv with no edges cutoff, however there is a small black border around the whole movie if I play it on another TV or on the computer. Do TVs work differently or something that you can have different fits on different TVs?

 

What you are experiencing is overscan.

 

Yes. The older TV's use to have adjustments on the back. The newer ones are getting harder to find with manual adjustments.

Example: Watching ESPN from the same cable company, the updated scores at the bottom of the screen (Ticker) cannont be read on my father's NEW TV, but can be on mine. You can see them, but not enough to make out what it says.

 

1.are you saying that if i plan to watch a movie through my DVD player to my 4:3 TV, it is not recomended to encode the movies larger then 640 wide?

2. i have LG DVX-9900 dvd player and before I upgraded the firmware, it would cut my edges too, for example if the movie is 16:5, or 16:6 it would cut the left and right side to a perfect 16:9 aspect, which was rather anoying, then i upgraded with fallenAngel's and i have no longer such problem, the movie will display any size i encode, even 100:1, then it will display a line in the middle of the screen

 

Yes. That is correct.

If you encode larger than 640 you may have problems with freezing or jerky playback.

I have a very fast computer and video card, and I tested this. I play xvid from my computer and watch it on my TV. I don't burn to disc. (Thought my resolution would be better on the TV the larger I made it). But, it did have jerky playback about every 5 - 8 seconds. Not much, just nano second pauses. Plus, the picture was not better. Looked the same to me.

 

is this why sometimes i get pink or green boxes in the darker areas of a scene. it is not something big but it is anoying, the boxes appear blend togather for 1-2 sec max, not more then 5-6 times during the entire movie, and only when i play them on my TV, my PC douesnt have this problem

 

This is on a standalone player? The higher the res, the more chance of bitrate spikes, which lead to buffer underuns that could cause what you describe. Shouldn't happen with proper VBV settings, no matter the resolution.