How to determine proper video size and aspect ratio?

[Bonie81]

i hv several odd size video files, for example
Width : 352 pixels
Height : 480 pixels
Display aspect ratio : 4:3
Frame rate : 29.970 fps

How to select between 720x480 or 720x576 or any other proper video size and aspect ratio to convert those files?

[Baldrick]

It's 4:3 so convert to 720x480 4:3 ntsc. Or if you are making a dvd can you keep it in 352x480. It's a valid dvd resolution.

[Bonie81]

Baldrick

thanks for reply
i just converted small sample to avi
720x480 4:3 29.97fps looks ok to me, but,
720x576 4:3 29.97fps looks more detailed.

thanks!

[guns1inger]

720x576 4:3 @ 29.970 fps is not DVD compliant. If you are not making a DVD then this may not matter to you, but in that case, why resize ?

[Cornucopia]

720x576 4:3 @ 29.970 fps is not DVD compliant. If you are not making a DVD then this may not matter to you, but in that case, why resize ?

Again, if you AREN'T making a DVD, why resize? PCs with apps like VLC can play this fine as-is.

And

IF YOU ARE, why resize?

352x480 @ 29.97 is totally DVD-Video compliant for NTSC systems. It's known as 1/2 D1. The 352x480 looks like it wouldn't be 4:3 (because the "SAR" = 0.7333), but it REALLY is 4:3 DAR.

Any resize will LOSE QUALITY.

(And 576 more quality? I don't think so. Just because you're using more pixels doesn't mean they're being used WELL. A 352x480 converted to 720x480 doesn't do ANY resize in the vertical dimension, so it wouldn't lose quality because of resizing, whereas 352x480 to 720x576 resizes in BOTH directions - with attributable loss. And both will lose a little because of reencoding).

Scott

[creamyhorror]

A 352x480 converted to 720x480 doesn't do ANY resize in the vertical dimension, so it wouldn't lose quality because of resizing

Wait, really? Resizing in one dimension doesn't reduce quality? Could you point me to a reference?

[Bonie81]

VLC plays perfectly with nice resizing automatically. I LUV VLC.

While playing in Windows media player gives me boxed weird look, and does not offer much choices for pan-scan or re-size, so i wanna re-size, i thought there might be something wrong with source files.

By the way I tried both 720x480 and 720x576, but I like 720x480 more.

Thanking all you who replied this post coz all the replies and details provided by you, all, is very informative.

By the way i am not making any DVD, its all my collection of Very High Q (9000kpbs / 640 5.1 SS) personal memorable Clips.

Tks!

[EddyH]

A 352x480 converted to 720x480 doesn't do ANY resize in the vertical dimension, so it wouldn't lose quality because of resizing

Wait, really? Resizing in one dimension doesn't reduce quality? Could you point me to a reference?

Wellllll depending how good your player is, it might not auto-smooth a 352-width video on output, so you get some distracting extra pixelation. The extra bandwidth requirement and processing for upscaling it might be worth it for a smoother picture on poor hardware.

I'm guessing OP has downloaded a straight rip of some CVD, longplay home-recorded DVD or similar... hmmm.

The big issue here though is that old bugbear - vertical resizing of potentially interlaced material. Whereas this way you can at least get a near-identical 352-width file back later if you so wished.

Can I just retweet for emphasis DO NOT RESIZE IT TO 576 LINES HIGH. BAD IDEA. Unless you REALLY need to do a NTSC->PAL conversion for some reason, in which case there's a few more steps involved than that....!

Going to DVD: It will be fine as-is, unless you have a rubbish player, in which case, 704x480 is your safest bet. Don't expect it to look any "better" other than being less pixelated though - increasing size does NOT improve detail. Resizers don't have psychic powers.

Use on PC: Either find how to tweak the file so Windows player recognises it as a 4:3 file (not 11:15!), do the sensible thing and use VLC, or convert it to MP4... with full deinterlacing if needed, to some intermediate resolution like 512x384 (or 640x480 if you really have to). Both MPG and AVI (MP4, Divx, whatever) have provision for setting the playback shape inside the file, but support for it is unfortunately patchy, so if you convert, it's best to use a "square pixel" setting.

BTW Bonie, why do you even WANT to pan-scan a 4:3 image, or at all on a hi-rez PC screen?
And how come they're only 352 wide if the rest of the settings (maxed bitrate, surround sound) are so high?

[Cornucopia]

Not even counting the interlace bugaboo (which is huge!! as Eddy H mentions), resizing is primarily a matrix algebra process. So it's POSSIBLE that a 480 to 480 resize would be DUMB enough to blend, etc. but I would NEVER used an algorithm that resized in such a way. You've got a grid of pixels in 2 dimensions; a resize would choose a dimension and blend/interpolate to the new size, and if there's the same input and output numbers in a dimension, a smart program should LEAVE IT ALONE. Similarly, a smart program would treat doubling/halving, etc in special ways to improve quality.

Loss is incurred on audio or video in 2 areas:
1. Rounding errors due to signal processing (and interpolation from resizing falls under this)
2. Rounding errors and (re-)Quantization errors in LOSSY compression.
(2 is much worse, but you want to avoid both if you can)

Scott

[creamyhorror]

So it's POSSIBLE that a 480 to 480 resize would be DUMB enough to blend, etc. but I would NEVER used an algorithm that resized in such a way. You've got a grid of pixels in 2 dimensions; a resize would choose a dimension and blend/interpolate to the new size, and if there's the same input and output numbers in a dimension, a smart program should LEAVE IT ALONE. Similarly, a smart program would treat doubling/halving, etc in special ways to improve quality.

Yes, I'm assuming 480-to-480 results in no change vertically (no retarded algorithms). What I'm saying is that, surely the horizontal resize has a degrading effect? Less than with a two-way resize, but certainly a real one.

[Cornucopia]

Does the horizontal resize have a degrading effect on the vertical resolution? It shouldn't (if it's using smart algorithms).

Here's an example (assume these are monochromatic/greyscale lightness values):

01___05___09___13
17___25___01___17
01___13___13___01

So this is a 4 x 3 grid. You want to resize to 7 x 3? Using a nearest-neighbor algorithm (based on only 1 dimension each, with a "border lock"), you'd get...

01___03___05___07___09___11___13
17___21___25___13___01___09___17
01___07___13___13___13___07___01

If you don't have "border locking" (my term) the edges would have to get their values from somewhere. Maybe it gets influence from "wrapping around", maybe it extrapolates based on the side opposite the edge. And there are a number of algorithms beyond "nearest neighbor". And the algorithm would have to choose whether or not to REPLACE EXISTING pixel values if they exactly match positioning from original to final size...
That's why there's a variety of resize algorithms & programs, some of which charge $$$ because they're very "smart".

Scott

[creamyhorror]

Does the horizontal resize have a degrading effect on the vertical resolution? It shouldn't (if it's using smart algorithms).

I'm referring to a degrading effect on horizontal resolution.

And the algorithm would have to choose whether or not to REPLACE EXISTING pixel values if they exactly match positioning from original to final size...

Isn't this why there's always a degradation? There are going to be errors in resizing, unless it's a neat doubling/multiplying of size.

Basically, I'm arguing that resizing even in one dimension reduces quality (whether negligibly or significantly) so it should be avoided if it isn't necessary. The only exception being if the resize allows the video to be played back on the target device without further resizing.

[Cornucopia]

Does the horizontal resize have a degrading effect on the vertical resolution? It shouldn't (if it's using smart algorithms).

I'm referring to a degrading effect on horizontal resolution.

And the algorithm would have to choose whether or not to REPLACE EXISTING pixel values if they exactly match positioning from original to final size...

Isn't this why there's always a degradation? There are going to be errors in resizing, unless it's a neat doubling/multiplying of size.

Basically, I'm arguing that resizing even in one dimension reduces quality (whether negligibly or significantly) so it should be avoided if it isn't necessary. The only exception being if the resize allows the video to be played back on the target device without further resizing.

Yes, of course resizing at some point causes degradation. That's what I was saying earlier about loss due to rounding errors. That's also what we were saying earlier about LEAVING IT ALONE (we said that also, not just you). TVs and monitors don't have a 352x480 4:3 dimension, so somewhere along the way there's going to have to be a resize done. Either resize NOW to a standard resolution (720x480 @ 29.97) or leave it alone and let the video player/tv do the resize on playback. If you were authoring to DVD anyway, you have much less work to do by leaving it alone.

But if you have to resize (and you do here), resizing in one dimension is much better than resizing in 2. Of course, depending upon the resize algorithm your milage may vary and that may make you choose a different course...

...hmm, I notice that the OP hasn't replied in a while. Just us techies bargaining over the finer points...


Scott

[creamyhorror]

Yes, it's just a matter of interpretation thing. I thought your initial statement implied there was no quality loss as long as the resizing was only in only dimension, but you've clarified it.