new Virtualdub MPEG - still a colorspace problem with MPEG-&

[sanlyn]

I still see many posts in the forum concerning the VirtualDub bug with MPEG to AVI (RGB24) conversion. These posts pre-date the latest edition of VirtualDub and its MPEG plugin. The complaint was that VirtualDub treated incoming interlaced MPEG as progressive and caused some color channel problems when converting to AVI.

I just tried a few quickie conversions with some old MPEG with the new VirtualDub plugin. I don't see any problems. Does anyone still see a bug with the new plugin?

On the other hand, MPEG->AVI conversions are something I seldom need to do, except recently. I recorded several hours of the Obama inauguration directly to DVD, but had to split the recording into 4 shorter DVD's. To do so, I broke the recording into several 90-minute sections on my DVD recorder's hard drive, burned them to DVD, then copied the videos to my PC. I cut several seconds of scenes I intended to use as segues for the end and beginning of each DVD. I converted the clips to AVI in VirtualDubMPEG2 (the new plugin was not yet released). I used VirtualDub on the AVI clips to create a fade-to-black at the end of one DVD and fade-from black for the beginning of each successive DVD. Then I re-encoded the doctored AVI clips to MPEG2 in TMPGenc-Plus. In every case I had to join the fade-out portion of each end, or the fade-in of each beginning, with the previous or next frame from an unconverted MPEG section (My editor for all this cutting and joining was TMPGenc MPG Editor v2). Between frames, I saw no difference in color at the patch-in points -- none at all. I played the finished videos on 3 PC monitors, 2 LCD tv's, a CRT tv, and 42" and 50" plasmas, at both regular speed and frame-by-frame, sometimes zoomed-in. I have yet to detect any problem at the point where the re-encoded frames were joined with an original, unconverted frame.

Back then I didn't have time to go thru the MPEG->AVI conversion with AviSynth (using DGMPGDec) to feed the MPEG clips to VirtualDub. I realize I could have used other software to affect the fade-out and fade-in without going into AVI, but that software wasn't available on the PC I used.

[jagabo]

The problem is still there in version 1.9.2. It can be hard to see with real world video. But easy to see with cartoons and test partterns. A sample from an interlaced DVD:

vts_01_6.mpg

Compare VirtualDub and VirtualDubMod. The latter handles interlaced YV12 properly. Crop from an interlaced DVD, VirtualDub on the left, Mod on the right:



only one field (other field black):



The simple fix for VirtualDub is to use DgIndex and AviSynth to convert to YUY2 or RGB:

Mpeg2Source("filename.d2v")
ConvertToYUY2(interlaced=true)

or:

Mpeg2Source("filename.d2v")
ConvertToRGB(interlaced=true) #since VirtualDub will be working in RGB anyway

I'm using this MPEG 2 plugin: http://home.comcast.net/~fcchandler/Plugins/MPEG2/index.html which is the newest I've found.

[sanlyn]

Thanks, jagabo. Those are the scripts I used in the past (all the newest versions). I just haven't done MPEG->AVI that much, but likely I'll encounter this problem sooner or later. Come to think of it, I didn't use vanilla VirtualDub, I used the mod mentioned here. The DVD I mention here is one of the first such conversions I've done in a spell, and you could well be correct -- maybe this particular MPEG didn't present the problem so dramatically. I give it another look.

Thanks again.

[jagabo]

maybe this particular MPEG didn't present the problem.

It has the problem, it's just hard to see unless you have large motions with very different colors.

[sanlyn]

Yup. Just made some quickie captures and zoomed-in with Photoshop. The bug is there -- just barely, hard to see because there's so much detail in the scenes. The fade-in/out clips are only 3.5 seconds, and the darker frames reveal little. But, yep, 'tis there. Gimme a weekend and I'll remake those transition scenes. From now on I'll go back to using the AviSynth script.

[jagabo]

At least I'm not the only that sees it now!

[sanlyn]

At least I'm not the only that sees it now!

Never fear. Not only did I see it when comparing frames, but I've read many posts by other, actually sane people who see it, too. And I revise my previous statement: I didn't use VDubMod, I used plain VDub without the AviSynth script. Remnants of the project were on the one PC where I never installed Mod.