The wall!! The wall.. it is coming alive!

[cogd115]

Well, I thought I was watching a horror flick when I was watching Chinatown freshly encoded in xvid with Gknot. The background started moving from the very intro! Well, almost..

The background color was smudging like watercolor. When I closely inspected, it was as if there were a thin layer over the background, and the layer were morphing around, which created the illusion that the background, expecially the wall, was coming alive. When Jack Nicholson's head accentuated with the dark brown hair moves against the background of the wall, the effect gets worse around Jack's head -- lots of pixel movements, sheesh.

Has anyone encoded Chinatown and noticed a similar thing? What is this about? Is this some type of artifacts related with xvid setting? Is there anyway or a filter (encoding) to tone it down at least?

By the way, my setting was motion search of 6, qpel, chromo motion, global motion compensation, vhq mode of 4...

[bond]

try to search the forum for qpel and smearing! perhaps that is what described? did you use one of the latest xvid builds? nic or koepis? (no, devapi4 is not meant for encoding atm only testing)

[cogd115]

I read the long thread in the xvid forum regarding qpel. It seems that I am having the same problem a few mentioned in the thread -- especially, the moving army of pixels.

After Chinatown, I encoded Glengarry GlenRoss in the same setting including qpel. Wow, the problem was far worse with that movie as the probem peculiarly gets worse with "wall" or blurry backgrounds, and Glengarry GlenRoss has an army of wall and blurry backgrounds in the office! I saw an army of pixels coming alive all over and throughout the office scenes which are about 80% of the movie!

So, I used Xmepg and encoded a short clip of the movie without qpel and noticed that the problem got toned down quite a bit. Although some pixels are grainy, they at least do not morph around like the blob or the stars in the Starry Night by Van Gogh :D ....

I checked through the movies I enceded before and found that some of them suffer the same problem. Ouch! Neverthless, the pattern is that the problems outstands in older movies with less resolution, blurry scenes, etc. Even newer movies with walls or hazy backgrounds seem not to be excluded from the effect.

I am re-encoding Chinatown and Glengarry GlenRoss. I am glad to have found this anomalry before I got more movies down without being aware of this.

Thanks, bond. Qpel now doesnt seem to be worth it.. Grrrrr....

[KpeX]

You're definitely not doing anything wrong IMO, cogd115. One of the major flaws I notice of the current mpeg-4 implementations, including xvid, is how they handle texture and shaded surfaces such as you describe. With xvid, this problem is definitely elevated when using qpel with low bitrates. I normally don't use qpel at all for 1 cd rips, except for highly compressible movies. When the bitrate is available, however, qpel does an excellent job of retaining the detail and grain-look of the original DVD.

[cogd115]

Thanks for the reply, KpeX. I am glad to have confirmed that it was not me! :D Well, it was me, tho -- after all, it was I using qpel without having done a thorough research on it.

One thing I might wanna add, tho, is that the bitrates for the those movies were quite decent. For Chinatown, about 1400 kbit/s with about .25 pixels*frame while for Glengarry GlenRoss, more bitrates and pixels. While Qpel did a wonderful job on Star Wars: Attack of the Clones, it really did badly on older movies such as Taxi Driver, The Exorcist, The Thing, etc. in Technic-color... Even Reservoir Dogs. All recorded with decent bitrates. Perhaps, I should have used more bitrates like close to 2000??

Man, do I have to redo all these movies slapped by qpel?????? Well, I will redo them when a better version of xvid and better technologies all together.. :D

[KpeX]

Well bitrate isn't always a good measure of these things - video and the compression of it gets complicated enough that it's rather random and chaotic in a way - it's quite possible a movie at that bitrate might have problems with qpel, and it also depends on what you'll be watching the movie on - on my setup, my TV displays smooth textures and backgrounds much better, whereas typical 'moving' effects as you describe seem to look a little better on a computer monitor. But I have definitely come across movies where qpel does not produce a pleasing effect ( to my eyes ) at any (sane) bitrate.

btw I didn't remember seeing what build of xvid you were using - the more recent kopei/nic builds have definitely seemed to improve qpel recently (without doing any definitive testing)

[manono]

Hi-

Yes, as KpeX says, this is a tough problem common to MPEG4 codecs. However, I do think that XviD is better than the others in this regard (better than DivX5 and DivX3.11 anyway). I don't know if Q-Pel is such a good idea to use with older movies anyway, as they're noisy enough to begin with, and it just adds to the noise, and the likelihood of moving backgrounds.

You didn't give all your settings, but here are some things you might try:
1. I hope you're not using Koepi's old Stable build from last year. XviD has come a long way since then. Use the more recent unstable builds.
2. Definitely use VHQ.
3. Try a temporal smoother with the older grainy/noisy movies, like perhaps the TemporalSoften(2,3,3,mode=2,scenechange=6) from GKnot.
4. I've recently started using coloryuv(opt="coring") which controls the blockiness and moving backgrounds in really dark areas by making them all black.

Of all the movies you mentioned, I've only encoded The Thing (the John Carpenter/Kurt Russell remake version, right?). I just did it yesterday, as a matter of fact. It's a really dark movie, and that ColorYUV line did an excellent job on it. It also works pretty well on that white crap that trails behind when you encode the scrolling white on black end credits at a higher quant.

[cogd115]

Well, I stayed up almost all night trying to fix a problem of wrong timestamping of the subtitles. Of course, I have been unsuccessful at it wasting about 4 hours on it. Haha... I came back here to check a bit more on subtitles -- tired, depressed and angry at the same time. :D And... I find manono's post full of the enigma like code -- you know that German code of the WW2 -- coaxing me to spend more time and efforts into this -- mostly in futility, I am sure. :)

At any rate, I have been using the build that came in package with Xmpeg. The installation file says Xvid(nic), so I assume it has something to do with Nic's version. I searched the fora about finding out the version of xvid, but it seems I am not able to find precisely which version it is. So, I downloaded Kopei's, and somehow the preview of Gknot does not find it compatible or useable. So, I reinstalled the previously mentioned one now.

Other settings i did not mention are all at default.

I will search and study a bit more on "temporalsoftening" and "coloryuv" and ask you more questions about them..

The Thing turned out to be one of the better encoding jobs I did on older movies. The background does not move like it does on Glengarry GlenRoss. Nor does it smudge badly like the Exorcist. But.... Well, I gotta try your setting -- after I figure out what the heck they are. :)

I feel discriminated whenever I come to this site. Intellectually discriminated, that is.. :D

I gotta slow it down.. So far, I am more or less wasting my cds.. I can probably salvage about 5 movies out of about 30 I stored on cds... LOL...

thanks once again guys..