"Washed out" mpeg from AVI conversion

[gg2004]

Hello guys,
I have been trying to convert downloaded AVIs into mpegs, but find the resulting videos to be "washed out", with noticeably less color contrast and saturation compared to the originals.
My inputs are XviD and DivX of reasonable resolution (640x480, 512x384) in PAL format, and I have used both Mainconcept's standalone encoder (1.5.1) and VSO's ConvertXtoDVD (2.2.3) to convert them to DVD PAL (720x576). I played with most tweakable settings in the programs (conversion quality, deinterlacing, RGB switch, etc) to no avail. Interestingly, the Mainconcept and ConvertXtoDVD outputs are very similar to one another in color and contrast. The AVIs are YUV420p, as are the converted mpegs.
Any ideas that might help pinpoint the problem?
Thanks much in advance!

ORIGINAL AVI (640x480, resized to 720x576)


CONVERTED MPEG (720x576), ConvertXtoDVD Hi-Qual



ORIGINAL AVI (512x384, resized to 720x576)


CONVERTED MPEG (720x576), ConvertXtoDVD Hi-Qual


CONVERTED MPEG (720x576), MainConcept 6000 average bitrate

[manono]

Hi-

Any ideas that might help pinpoint the problem?

Yeah, it's a colorimetry issue. Your AVIs are some form of Rec.601 and those encoders are expecting Rec.709. There are several things you can do to fix it:
1. Use TMPGEnc for your MPEG-2 encoding as it's the only one with which I'm familiar which assumes Rec.601.
2. Use AviSynth to frameserve into your MPEG-2 encoder with the ColorMatrix filter properly applied. Quoting from the doc:

In case you captured something or you have a XviD/DivX (both are encoded Rec.601 coefficients),
and you want to encode it to mpeg-2 using CCE (which assumes Rec.709 coefficients), you should use the following script (progressive material)

ColorMatrix(clip, mode="Rec.601->Rec.709")

There are several ways to convert a YUV stream to RGB. The most well known one, uses Rec.601 coefficients. It is for example used in the color conversion routines of AviSynth, VirtualDub and XviD/DivX. When playing back a XviD/DivX the stream is converted to RGB using Rec.601 coefficients. The main issue is that sometimes other coefficients are used for the YUV to RGB conversion (the other two are Rec.709 coefficients and FCC coefficients). A problem arises if a stream is encoded using one set of coefficients (Rec.709 coefficients for many dvd streams for example), and somewhere in the reencoding-processing-playback chain a different set of coefficients is assumed (Rec.601 coefficients for the XviD/DivX decoder or FCC coefficients for TMPGEnc/QuEnc or Rec.709 coefficients for CCE). You will get a slightly color distortion, which looks like a change in brightness (it's not really a change in brightness, the colors are just slightly off).

Or use other AviSynth filters to do the same thing.
3. Learn to use a Levels or Brightness or Contrast or Saturation filter to fix it. More information:

http://forum.doom9.org/showthread.php?s=&postid=514595#post514595
http://forum.doom9.org/showthread.php?s=&threadid=81191

However, the chances are excellent that the original encoder didn't know about the issue, and you're just bringing them back to the way they were originally, if originally from a DVD using Rec.709.

[gg2004]

Thanks Manono, that's phenomenal feedback! I suspected a colorspace issue, but was not conversant enough with the subtleties...
Most of my AVIs are actually Sat TV captures performed in Europe by who-knows-who, but a few others are from DVD sources and it's conforting to know that I might be restoring them to their original, less-saturated look.
I am reasonably familiar with TMPGEnc and will give it a try to see how it differs from the other two, but I must confess that I'd rather use an easy-does-it converter like ConvertXtoDVD, since we are talking about hundreds of files here... maybe I'll drop the author a line to see if he would consider a Rec.601/709 switch in future updates.
On a related note: is the color space stored in the AVI's header, and is there any app you know that will list it? I generally use GSpot and DRFAnalyzer, but they are not helpful in that respect...
Thanks again, and best regards

[manono]

Hi-

Colorspace is a different issue. All the DivX/XviD AVIs would be YV12. I don't use either of those 2 encoders, but I suspect they want YUY2 input. I do DVD2DVD conversions, usually using CCE, and always add in the ConvertToYUY2() line to my AviSynth scripts, since DVDs are YV12. I don't know how that affects your issue, if at all. This is more in jagabo's line of expertise than mine, and as soon as he spots this thread I suspect he might have something to say.

I don't cap either, but as I understand it all Standard-Def caps are Rec.601, and all Hi-Def caps Rec.709. DVDs are usually, but by no means always (about 75/25 in my recent experience), Rec.709. Here's a couple of threads from a fellow that caps and was having the problem:

http://forum.doom9.org/showthread.php?t=127907
http://forum.doom9.org/showthread.php?t=128801

On a related note: is the color space stored in the AVI's header, and is there any app you know that will list it?

If MPEG, you can get the colorimetry from DGIndex by running the Preview. You can also get it (the colorimetry, not the colorspace) for both MPEGs and AVIs from GSpot. The thing is, if it says nothing, it's being decoded as Rec.709, whether or not it really is. The discussion in that first link was partly about the caps not having the colorimetry specified, and being decoded incorrectly. Anyway, in this portion of a GSpot screen of an M2V from a DVD you can see I470 highlighted. That's identical to Rec.601.



But as I said, I don't pretend to be an expert in this area.

[gg2004]

Thanks again Manono, I am learning a lot as I go along!
I did a quick test with TMPGEnc, checking and unchecking the "Output YUV data as basic YCbCr not CCIR601" box, and lo-and-behold, checking the box yields colors much more similar to the original. I pasted an example below, since I can no longer edit my original post.
From a theoretical standpoint, I am still a bit confused because this is most likely a standard definition cap (hence R601 from your explanation), so the "output as CCIR601" option on TMPGEnc (box unchecked, to be clear) should give the better match, not the other way around... Nevertheless, outputting as basic YCbCr gives me the original color saturation (seemingly even a bit more than the original, but let's not be picky as other variables might be involved)...

ORIGINAL AVI (512x384, resized to 720x576)


CONVERTED MPEG (720x576), TMPGEnc 6000 max bitrate, basic YCbCr


CONVERTED MPEG (720x576), TMPGEnc 6000 max bitrate, R601


CONVERTED MPEG (720x576), ConvertXtoDVD Hi-Qual