HDTV video levels? [Archive]

D-Train

4th August 2005, 22:14

I've been happily filling up my hard drive with HDTV recordings... so much so that I need to make room. I started by experimenting with re-encoding to Xvid, WMV-9, and the like. The guides I've read usually use Avisynth with DGMPGDec. After trying this I immediately noticed that the re-encoded files looked more washed-out when playing from the PC. Otherwise the quality looks great.

I then tried capturing two comparison frames using VDubMod:

The first frame I used VDubMod to open the .mpg file directly -
HDTV via MPEG-2 (http://i10.photobucket.com/albums/a114/D-Train78/mpeg-csi.jpg)

The second frame I used VDubMod to open a .avs file -
HDTV via DGMPGDec (http://i10.photobucket.com/albums/a114/D-Train78/avs-csi.jpg)

Here was the script I used for this test. As you can see it's very simple:

loadplugin("C:\Program Files\dgmpgdec1012a\DGDecode.dll")
mpeg2source("csi.517.compulsion.d2v")

If you compare the two frames using the "TV" logo in the upper left corner for reference blacks and whites the color is definitely different between the two frames. What's going on here?

My apology in advance if this isn't the right forum for this.

Kika

5th August 2005, 10:06

Looks like VDubMod handles the Lumarange different to AVISynth.

My guess:
VDubMod: The Range is stretched to 0-255
AVISynth: The Range is at normal state (16-235)

D-Train

5th August 2005, 17:51

If that's the case then would it mean my DVD decoder software is also stretching the lumarange during playback? If I watch the original .mpg in something like WMP and then watch the .avi I create, there is a definite difference. Also, if I save a BMP using DGDecode the result is the same as when opening the .mpg in VDubMod.

Thanks for the reply!

hrlslcbr

27th August 2005, 00:56

Try using VMR9 for playback. It doesn't stretch the video levels.

neuron2

27th August 2005, 01:55

You're converting to RGB for display in VDubMod, so DGIndex's YUV -> RGB option comes into play. Check how it is set.

D-Train

2nd September 2005, 21:12

Thanks for the suggestions. I think what happened is that I was using Full Processing Mode, and there was a conversion to RGB during the video processing chain? I figured out to use Fast Recompress instead. I believe this ensures that there is no conversion from YV12. I could be wrong though... wouldn't be the first time. In any case the videos look great.