KVCD: Trouble Compressing Reds in Video?

gonzopdx · #1 02-05-2003, 01:27 PM

@kwag

I just watched two of my one-disc encodes, one encoded MPEG1 and the other MPEG2.. in both of them, in scenes where there was a lot of red, the quality of the picture seemed to drop dramatically. The two movies I noticed it in was in Chicago and The Thing -- Chicago has a lot of scenes with red lighting and The Thing as well. In Chicago, there is a part where the lighting changes quickly from red to blue, and there is an almost instant change in quality (seems like once the GOP caught up, the quality went back to normal).. I'll post clips soon..

Anyone else notice this?

gonzopdx · #2 02-05-2003, 05:39 PM

Here is the sample.

This was encoded using Notch 1a and CQ of 60-something if I remember correctly.

It might not be very apparent watching it on your computer -- if you pause at any point during the scenes with a lot of red, you'll notice lots of artifacts all over the picture (more than usual), including in the background and on the characters.. It is VERY apparent when watched on the TV -- maybe burn it on a CD-RW and watch the sample on a TV..?

What do you think?

EDIT: It also seems to get progressively worse through the red scene, then when it switches back to normal/blue light, the artifacting/noise is back to very little (regular amounts)

EDIT: Or maybe the red just makes it more noticeable..?

kwag · #3 02-05-2003, 06:28 PM

Hi gonzopdx,

Ok, I watched the sample. Definitively the CQ is too low for that type of film, or you didn't use the appropiate filters. Did you use FaeryDust() and TemporalCleaner()

Because if you didn't, that would really help on that type of film

What is your .avs script?

-kwag

gonzopdx · #4 02-05-2003, 10:55 PM

I'm not sure if the CQ was 60 or if it was higher -- it may have been 76

But the quality throughout the rest of the movie is fantastic! It's just when there's a lot of red on the screen that the quality drops, then as soon as the red disappears the quality shoots right back up. I prefer not to use C3D or Dust unless I absolutely have to because it seems that it smooths the image too much and it loses a lot of detail..

My encode of The Thing, which had a CQ of 78, also displays this problem.. I'm pretty sure it's not the .avs script or the CQ, but the encoder's handling of reds or too much red..

My .avs is typical..

Code:

(...plugins...)

source()
Trim()
Crop()
LegalClip()
Resize()
FluxSmooth()
BlockBuster(noise .3)
LegalClip()

...?

kwag · #5 02-05-2003, 11:01 PM

Hi gonzopdx,

Give SpaceDust() and TemporalCleaner() a try

-kwag

MrTibs · #6 02-07-2003, 12:05 PM

I don't know if anyone else has noticed this but...red seems to give Mpeg1 and Mpeg2 a hard time.

I recently rented "Signs" on DVD and I noticed that a scenes showing the red walls that had losts of macro blocks while the rest of the movie is excelent. (I'm talking about the scene where we watch the wall as we listen bumgs going on outside) I've noticed this same problem with red on some other movies also.

I guess what I'm saying is the problem may be with the source.

labomba · #7 02-07-2003, 12:40 PM

Same here. In my Insomnia encode, even with spacedust() and temporalcleaner(), I got more blocks on red scenes. Like when AlPacino is in his room trying to sleeping. A low action scene, more red by the afternoon's athmosphere of the room. I'll send a clip, if I can match it.
LaBomba

kwag · #8 02-07-2003, 12:51 PM

Anyone tried BlockBuster "Noise" with a level of .7 or .8 on these scenes

labomba · #9 02-07-2003, 01:11 PM

Nope. I could try it later. Could you give me some hint how to test this filter only in few scenes. Should I make a clip, cutting the film, and then testing some filters? How is the sequence and the tools?
LaBomba

kwag · #10 02-07-2003, 01:21 PM

Quote:

Originally Posted by labomba

Nope. I could try it later. Could you give me some hint how to test this filter only in few scenes. Should I make a clip, cutting the film, and then testing some filters? How is the sequence and the tools?
LaBomba

Just select a source range in TMPEG and encode only that portion.

-kwag

labomba · #11 02-07-2003, 01:36 PM

Quote:

Originally Posted by kwag

Quote:

Originally Posted by labomba

Nope. I could try it later. Could you give me some hint how to test this filter only in few scenes. Should I make a clip, cutting the film, and then testing some filters? How is the sequence and the tools?
LaBomba

Just select a source range in TMPEG and encode only that portion.

-kwag

Sorry Kwag.
I don't know how to select a souce range in TMPEG

.
I even tried to open it and look around before reply you, but I can´t see where I can select ranges in TMPEG. Would be on the .avs script or something like in VDub.
Sorry again!

LaBomba

kwag · #12 02-07-2003, 01:42 PM

Run TMPEG. Then click on "Settings" then click on "Advanced" and double click on "Source Range". Now you can play with start and end position.

-kwag

labomba · #13 02-07-2003, 02:28 PM

Awesome!!! I got a new trick!. With this I can look the output using one set of filters or another, only on the critic scenes. Really thanks! Another thing: are there any way to use specifcs filters on specifics parts, something like encoding the film "a la carte"

Labomba

kwag · #14 02-07-2003, 02:44 PM

Quote:

Originally Posted by labomba

Another thing: are there any way to use specifcs filters on specifics parts, something like encoding the film "a la carte"

Labomba

You could do it, but you would have to write functions in your avisynth script, in order to process different ranges with different filters. Not very amusing

-kwag

labomba · #15 02-07-2003, 02:50 PM

NO WAY!!

I really can live with these "little and candy"

Blocks at all!

Thanks.
LaBomba