red lights = pixelized image!

[breeder]

this is something that I noticed with some films where some scenes have red lights (mainly bars, discos, etc). In this particular film Jackie Brown (minute 43+) the image gets very pixelized :-\ no matter the kbits I use (the film have almost 1800 in average).
Any solution to this problem?

badddddd english I know I know :-)

[DJ Bobo]

This is normal
This is due to resizing, if you keep the original resolution you won't get that much "pixelisation" as you call it, but keeping the original resolution is also irrealistic, so you gotta live with it

[breeder]

hmmm but that only happens with in ambients with red ligths or in red surfaces, mostly strong or dark red, other colors dont have this behavior.

[Fox Mulder]

The human eye is more sensitive to luminace(light) than chrominance(color), but in a strong red or blue spectrum you will notice that lack of resolution, that you describe as pixelation. I think that is more a fault of the YUV(YV12) color space used in DivX, that discards much color information and pronounce this even more, in contrast to RGB color space(somebody correct me if I'm wrong).

[DJ Bobo]

@ Fox Mulder
MPEG2 files have also YUV color. But I don't think it has anything to do with it being YUV or RGB.

@ breeder
All flashy colors are so, and especially red. I discusted about it with some friends of mine, they thought it was because of deinterlacing, but that's not true, since it happens also with progressive videos. As said, it's a resolution issue, if you keep the hi res you won't notice it, if you resize to a lower resolution, you'll get that stairs effect on flashy colors and especially on red, there is NOTHING you can do about it.

[breeder]

eheh :-) ok

[cordraconis]

look at the 2nd scene of U571 with the red light.
pay attention to the knuckels of the captain's fist.

I noticed this when I converted the movie, so I did more tests to see if I could eliminate the artefacts.

Results: Using "Neutral Bicubic Resizing" in DVD2AVI, gave less Red-blockyness. Sharp and Soft Resiz. made it (hardly noticeable) worse.

I guess this is because indeed, the Red light is in the lower end of the spectrum, and thus higher wavelenght, thus less detail. (And maybe the Mpeg-4 codec uses even less bits to represent these chromina values).

In the rest of the movie, there is no problem with the red colours, as long as there are other colours present.

And as for the "DivX 3.11 Nandub SBC" goes, the same thing here, only a bit worse (bigger cubes). I downloaded a 2CD "backup" :D of "Blade II", with SBC and AC-3, and in the begin-logo (all red and black), the artifacts/pixelisation was clearly noticable.

Solution to this? none, I guess. maybe yet another codec?

greetz,

Cordraconis

[Difflam]

This may be totally off-track, but I believe the pixelation you are talking about is caused by the codec.

I remember learning at uni a while back that the human eye is less sensitive to detail with regards to viewing red things... and some codecs exploit this particular aspect of the human eye to reduce detail in red areas of the picture to save bits... but in some cases the effect is too severe and the blockiness is noticable, as in the case you mentioned.

[buba king]

i thought this happend because red and blue colors are harder to compress.. i cant say i see this effect on low bitrate mpeg-2 stuff (SVCD) tough..

[DJ Bobo]

I think, I found an explanation to this, look here: http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html & go down to "Chroma Upsampling Error"

[Soulhunter]

Hi everybody !

You shoul read this Threads too. Maybe it helps !

Heres the adresses:
> http://forum.doom9.org/showthread.php?threadid=38304 <
> http://forum.doom9.org/showthread.php?s=&threadid=57025 <
> http://forum.doom9.org/showthread.php?s=&threadid=41480 <

So, post back!

Bye