Standard XVID Frame Sizes

[adalect]

Hi there.

I recently got a video from the internet in MKV format. I like it, and am in the process of converting it in a format that my DivX Player likes. I use XVID of course, since I have more control of what is going on in the encodes.

The video is 720 x 480 in terms of frame size. However, it's 16:9 widescreen, and has DAR flags to keep it the right way. I heard that DAR flags aren't respected in all players, so I figured I might as well resize the video so the frame size is right for the aspect ratio.

My question: what are standard frame sizes for XVID? I want compatibility for my DivX Player, the Phillips DVP3960.


Thanks for anyone who tries to help.

[jagabo]

No, there are no "standard" frame sizes in Xvid. But you should stick with mod16 (integer multiples of 16) whenever possible. Or at least Mod8. Most Divx/DVD players will not play Divx/Xvid files over 720 pixels wide or 576 pixels tall. So stick with sizes below that.

[adalect]

No, there are no "standard" frame sizes in Xvid...Most Divx/DVD players will not play Divx/Xvid files over 720 pixels wide or 576 pixels tall.

Would my player struggle with sizes near 720 pixels? I think I have played something with a width of about 680 pixels and it worked fine; I am just afraid my player would struggle with the higher sizes.

Also, since there is no standard, are there any funny frame sizes that just don't work? By your language, it sounds like there aren't, by who knows.

Also, is "LanczosResize" a good resizing command? I saw it pop up a couple of times over here.

[jagabo]

I'm pretty sure the Philips 3960 can handle 720x480 and 720x576 frames as long as the bitrate doesn't get too high.

Regarding "odd" frame sizes: do not use mod1 (odd numbers like 1,3,5...) or mod2. Many players will choke on them. Mod4 is usually ok but mod8 and mod16 are more efficient. So avoid sizes like 641, 642 and 643. 644 (mod4) is usually OK but 640, 648 and 656 are better.

AviSynth's LancsozResize() and BicubicResize() are both sharpening filters and give pretty similar results. But along with the sharpening comes added noise (which makes the video harder to compress) and halos on very sharp edges. BilinearResize() is a softening filter. It will give slightly blurrier results. But noise will be reduced and you don't get halos. My general rule is: very sharp or noisy sources get BilinearResize(). Others get LanczosResize() or BicubicResize().

[guns1inger]

Resolution isn't the issue (provided you stick with 720 or less). Bitrate and other factors are more likely to cause you playback issue.

[adalect]

Thanks guys for your help. I really appreciate it.

[adalect]

Just crunched the numbers:

So would 720 x 400 be a good resolution for 16:9 video?

[NotSoEasy]

If your movie is ...

Aspect Ratio - Resolution

2.35:1 - 720×306
1.85:1 - 720×390
1.78:1 (16:9) - 720×404
1.33:1 (4:3) - 640×480

[manono]

If your movie is ...

Aspect Ratio - Resolution

2.35:1 - 720×306
1.85:1 - 720×390
1.78:1 (16:9) - 720×404
1.33:1 (4:3) - 640×480

Since the height for the first 2 is only Mod2, I don't think so. Even the third one is only Mod4, so, not for me. Didn't you read (and understand) what jagabo said?

[TJohns]

Using ASPECT CALCULATOR 2.1 I got the follow "approximate" resolutions (with the indicated error from "perfect" when using mod 16 sizes)

2.35 = 640 x 272 (-0.13%) 720 x 304 (-0.78%)
1.85 = 624 x 336 (-0.39%) 704 x 384 (+0.90%)
1.78 = 624 x 352 (+0.28%) 688 x 384 (-0.78%)
1.33 = 640 x 480 (0% perfect) 704 x 528 (0%)

[jagabo]

So would 720 x 400 be a good resolution for 16:9 video?

Yes. Just be sure to use sufficient bitrate. Bigger frames require more bitrate to maintain video quality.

[adalect]

Just be sure to use sufficient bitrate. Bigger frames require more bitrate to maintain video quality.

Thanks jagabo. However, doesn't bigger frames give off better quality in the end with the same amount of bitrate compared to a smaller frame? That's what I heard. Is my frame size a bit excessive then? I have a big 50in widescreen TV, and am just wondering. I am just confused.


Thanks for your help so far.

[creamyhorror]

Thanks jagabo. However, doesn't bigger frames give off better quality in the end with the same amount of bitrate compared to a smaller frame?

Not exactly. If your bitrate is too low and your frame too big, you'll end up with a crappier looking picture than if you used the same bitrate but a smaller frame. On the other hand, if your bitrate is too high and your frame size is too small, then you'll get a crappier picture than if you used the same bitrate but with a bigger frame.

That's what I heard. Is my frame size a bit excessive then? I have a big 50in widescreen TV, and am just wondering. I am just confused.

No need to downscale; just encode with a decent bitrate, and increase it if necessary. Maybe something in the range of 1300-1800, depending on your quality demands and the complexity of the movie. Or use quality-based encoding at q3.

[adalect]

Not exactly. If your bitrate is too low and your frame too big, you'll end up with a crappier looking picture than if you used the same bitrate but a smaller frame. On the other hand, if your bitrate is too high and your frame size is too small, then you'll get a crappier picture than if you used the same bitrate but with a bigger frame.

So there are no advantages for having bigger frames? I thought there were. From what you guys say, it's a balance between bitrate and frame size. If one is too high, it either destroys the quality of the video.

...use quality-based encoding at q3.

I always do that. I am not too concerned about bitrates, I always use Quantinizer values because I care a bit more about quality and am lazy in terms of guessing bitrates.

[jagabo]

It's a tradeoff between resolution and bitrate. The smaller the frame the less bitrate it will require to keep from breaking up into macroblock artifacts. But when you enlarge that small frame to full screen size it will look fuzzy. So people who are looking primarily for small file sizes (low bitrates) will decrease the frame size. People who are looking primarily for image quality will use large frame sizes and let the file size (bitrate) fall where it may.

[adalect]

Special thanks to jagabo for staying with me throughout this and helping me along the way.

And thanks to everybody else who contributed and helped me.