DivX/XviD true 16:9? Ever?

[Tom Servo]

I was wondering what you people think of true 16:9 non-squarepixel encodes? Do you think there'll be ever an option for it in DivX or XviD? Would you use non-squarepixel encoding? One of the advantages would be a higher vertical resolution since you don't resize.

[Teegedeck]

MPEG4-streams (and that means XviD in this case) can contain aspect-ratio information. The support for it is there. The only problem is, there's no DirectShow filter as of yet that could interpret that info while opening the file and then automatically resize the picture. But the actual difference to what we do now in anamorphic encoding is only that resizing would happen automatically, that's all. As it is really just one click, why don't you just go ahead and encode anamorphically right now? I do it all the time. :D

[Tom Servo]

Encoding anamorphically reduces the vertical resolution. Resizing the non-squarepixel image using overlay/VMR functions preserves that resolution and stretches the picture horizontally into a correct aspect. That's what I mean. Slightly more detail if the bitrate ain't too low.

[Atamido]

One thing to add is to what Tom Servo said above is that anamorphic encoding is even better when you are encoding a DVD at full resolution. It means that you don't have to do any resizing of the video, which means you encode as close to the original as possible.

We have played around with this using an AR flag in MKV. Currently only TCMP is set up to read the AR flag and automatically resize, but it does work well. The benefit of keeping it on the container level is that you can use the same implementation on all video types, whether it be WM9, MPEG-4, or Huffyuv.

The main issue now is getting support in other players such as BS, Zoom, MPC, etc. Once that is done, there won't be much reason not to do anamorphic encoding.

[bilu]

Originally posted by Tom Servo
Encoding anamorphically reduces the vertical resolution. Resizing the non-squarepixel image using overlay/VMR functions preserves that resolution and stretches the picture horizontally into a correct aspect. That's what I mean. Slightly more detail if the bitrate ain't too low.

I think it's the opposite :confused:

Widescreen TVs stretch your display horizontally by 33%.
Anamorphic means stretching 33% vertically on encoding or playing to compensate this, without needing to zoom on TV which would crop the picture (= reduce resolution).


Bilu

[Teegedeck]

Originally posted by bilu
I think it's the opposite :confused:

Widescreen TVs stretch your display horizontally by 33%.
Anamorphic means stretching 33% vertically on encoding or playing to compensate this, without needing to zoom on TV which would crop the picture (= reduce resolution).


Bilu
It depends on what your source is; if you encode a DVD (that already is anamorphic) at full resolution you preserve all picture information of the higher horizontal resolution as opposed to discarding much of it in correcting aspect ratio before encoding. You don't zoom in horizontically on the result but 'squish' the picture vertically. If on the other hand your source is for example 4:3, you can do anamorphic encoding by reducing horizontal or vertical resolution, in order to save some bits, and resize to 4:3 in playback. This solution is not about keeping as much of the original picture information as possible but about a trade-off (lower quants vs. higher resolution) - but one that's still less costly for encoding TV-material than 'orthodox' resizing. I wouldn't condone the same thing if it was done for movies.

Anyway, I only thought of widescreen material when posting.

[ChristianHJW]

Anamorphic encoding mainly makes sense if your source is anamorphic, like for DVDs or SVCDs. I cant think of any other reason why a non-anamorphic source should be encoded anamorphic. After all, every resizing step will deteriorate the picture quality, of course only slightly. BTW, you may want to read here (http://forum.doom9.org/showthread.php?s=&threadid=54677) also.

[Zhnujm]

Originally posted by ChristianHJW
Anamorphic encoding mainly makes sense if your source is anamorphic, like for DVDs or SVCDs. I cant think of any other reason why a non-anamorphic source should be encoded anamorphic. After all, every resizing step will deteriorate the picture quality, of course only slightly.

Well, you have to resize it anyway if you want to play it on a 16:9 TV. If you dont do it during encoding your TV has to do it. Its just a matter of what looks better, the resizing via Filter or the resizing via TV.
I personnally like the resizing of my TV (increasing the size between the scanlines), but not many will agree with me, i think. :)

[Tom Servo]

My TV stretches the picture horizontally, so the vertical resolution is preserved. Resizing it before encoding would reduce it and cause the TV to zoom in. Something I'd like to avoid in DivX movies too, at least as option.

[Neo Neko]

I have a question. I have never messed much with encoding DVD anamorphic. But I do it with TV all the time. Does anyone know off the top of their head how to use AVIsynth's MPEG2 decoder plugins to either read in MPEG2 streams or DVD2AVI project files and extract the raw video without AR correction? That way you would not have to crop ever. Just resize 1:1, 4:3, or 16:9 whichever you preffer. And it might give better quality to boot.