mod 16 x264

[agilpwc]

I've always encoded with mod 16 resolutions. But recently began expirmenting with mod 8 and mod 4 because I want a particular resolution.

I don't see much of a performance hit, is there any "big" reason that I should absolutely stick with mod 16?

[bob0r]

No reason at all, maybe for compatibility reasons or certain rules, but for quality, there is not any visual loss for whatever resolution you use.
(1920x1080 already ignores the mod error by default)

[Dark Shikari]

The loss of non-mod16 encoding consists solely of the bits required to code enough extra lines of pixels to reach mod16. Its basically negligible.

[Ranguvar]

Wow, really? I thought mod16 made a very large compression loss. How about Xvid, is it worse to use non-mod16 there?

And if I can hijack this thread a touch, running off bob0r's post, should 1080p videos be encoded as 1080, 1088, or 1088 with the bottom 8 lines added as black?

[Selur]

it's not much even with xvid

[Dark Shikari]

Wow, really? I thought mod16 made a very large compression loss. How about Xvid, is it worse to use non-mod16 there?

And if I can hijack this thread a touch, running off bob0r's post, should 1080p videos be encoded as 1080, 1088, or 1088 with the bottom 8 lines added as black?I'm pretty sure Xvid does the same as x264 in terms of mirroring extra lines.

Padding with black is often worse than no padding at all because of the sharp line it creates.

[SeeMoreDigital]

it's not much even with xvidDown to MOD-8 perhaps...

But I'm not so sure the same is true when generating MPEG-4 Part-2 encodes at MOD-4 or MOD-2 resolutions. Also compliance in hardware playback devices (especially players fitted with Zoran Vaddis chip-sets) is erratic.


Cheers

[akupenguin]

Fore H.264, don't speak about mod8 or mod4. There is only mod16 or mod16-N (i.e. "the codec has to add N pixels to make it mod16"). Small values of N are good, in particular 2 is better than 4, and 4 is better than 8, and 14 is worst. But it's really not a large effect. Padding the input video is always worse than any possible nonaligned resolution.

Hardware players can bork anything. Of course the above applies only to compliant implementations.