DVD2AVI causes contouring?

[bobwillis]

Hello,

I use DVD2AVI as part of DVD2SVCD (in 2DVD mode using CCE). I have backedup several DVDs using this method, and have been extremely happy with the quality. This week via Ebay, I managed to buy a Dutch PAL version of the film 'The eagle has landed'. Looking for non-existant interlaced lines in it proved to me that it was a progressive source.

The picture quality of this DVD is poor, despite the main movie totaling over 6GB. However, the CCE backup I produced was dramatically worse, mainly lots of additional countour noise - where the colour in the re-encoding didn't appear to have sufficient resolution to accurately describe the original. So not being stupid or idle, I decided to encode a 1 minute clip and set about methodically adjusting the CCE settings and re-encoding; each time examing the result.

I have separately adjusted the DCT bias, the encoding matrices, the IQP value, tried CCE v2.50, v2.66, v2.67, adjusted the templates, altered the overall bitrate (even did a OPV Q=1 encode). All to no avail. Even with no compression, I cannot get something that resembles the source quality. I have spent all evening trying different things.

Then some light began to be shed on the subject. I previewed static frames in DVD2AVI and found that the picture quality improved if I changed from YUV to RGB32. By this I mean that the blockiness causing the contouring disappeared. I do not see this effect with other DVDs.

Also, the characteristic of the countouring (if set to YUV in order to show it) changed if I altered the iDCT from 32 bit MMX to 64bit or the IEEE setting. Large horizontal lines dissapeared from the contouring (these are not interlacing lines - the source is progressive). These horizontal bands (a few millimetres high) are something different. Re-encoding with 64bit removes these lines but I am still left with excessive contouring on a moving frame of a twilight sky.

All this led me to believe (possibly incorrectly - I am not slagging anyone or anything off), that the quality problem is being introduced by DVD2AVI. My question is: Has anyone seen this before? If so, what is happening and can anything be done to improve matters?

Any replies would be greatly appreciated - even if it is just an explanation of what is happening.

Best Regards,
Bob

[hakko504]

Good thinking: but for testing things like this you should use VirtualDub instead. Open the .d2v in Virtual dub with this simple AviSynth script:Mpeg2source(test.d2v)
ConvertToYUY2()
and look at the picture. Do you see the problem?

Now change the last line to ConvertToRGB32() instead. Does it look better now?

If the answer to both the above questions are no then I'd say that the problem is not with DVD2AVI.

[important edit] IIRC mpeg2dec3.dll will always decode to YUV format (YUY2 or YV12 depending on version), but to make sure, do two tests, one where the .d2v has been created with YUV setting and one with RGB setting in DVD2AVI and see if it makes any difference. [/edit]

If the answer to any of the above questions is yes, then you're right there might be a problem with DVD2AVI which needs to be investigated further.

And then you should redo the VD tests but this time use neuron2's version of DVD2AVI and mpeg2dec3.dll (links in the FAQ (http://forum.doom9.org/showthread.php?s=&threadid=59272) ) and see what happens. This requires the latest version of AviSynth (2.53) as well - and you get an extra test, with YV12 colorspace. Do you still have the problem? In that case you should post a short clip (<10s) so we can look at it and see what happens.

[another edit]Remember to close DVD2AVI before opening VirtualDub. FAQ Q27 (http://forum.doom9.org/showthread.php?s=&threadid=59272) [/edit]

[bobwillis]

Hi hakko504,

Many thanks for the reply. Yes, I can see the problem in Virtual Dub with YUY2 enabled. I can't tell the difference by converting to RGB32, presumably because mpeg2dec3 is always coverting to yuy2. I've tried using neuron2's latest files, but DVD2SVCD says they are not the right version and I don't know how to use the tools manually - sorry.

If you've got the time, I've prepared a short clip - approximately 8MB. Where can I upload it?

Regards,
Bob