Ways to prevent picture degredation?

[liverkick]

I have some fansubbed anime Im converting from Xvid to DVD. The quality is very good but not great, 640x360. On the source files there are very slight artifacts I guess you'd call them (sorry not sure the exact terminology for the distortions, some are blocky looking, others wavy) but you have to look for them. Yet when I convert to DVD, the distortion becomes much more noticable and pronounced. A lot more blocky and wavey distortions appear, especially on darker colored and lighted scenes. I use VBR multi-pass and higher bitrate (6k ave) doesnt seem to help at all. Both CCE and tmpg give me the exact same image quality degredation.

I assume this is just the nature of compression and converting, but Im still very new at this so Im not sure what I could be doing to minimalize the degredation. This is what Im using in avisynth right now fwiw...

AVISource("C:\.avi")
AddBorders(40,60,40,60) (my display was cutting off the image)
LanczosResize(720,480,0,0.5)
ConvertToYUY2()

Appreciate any tips...

[edDV]

The smartass answer is to find a source quality higher than Divx. Divx should be the last step and is squeezed to the max. You can't go home again.

[jimmalenko]

Why are you (redundantly) resizing when you're adding borders to make it 720 x 480 already ?

[lordsmurf]

Garbage in, garbage out

[vhelp]

Unfortunately, when it somes to divX/XviD (etc) sources, you take
your chances in quality of these formats. The majority of these
(video) files are poorly encoded. Mostly on account of users that
don't see the *true* imperfections of *their* encode method/process
when they view them inside some software AVI player. They only see
pc levels, of colors. This usually is seen as darker video, because
no OVERLAY is used, and the video is displayed in RGB color space.

When an AVI is played inside an OVERLAY window (assuming that it can
and that there are software that feature this) the video is lighter
in color space. Usually around [IRE 0 / 16-235] spec. But the driver
can switch to [IRE 7.5 / 0-255] (if you know where to search. course,
None of this is going to help you. Worse case, it will exagerate even
worse results.

When you convert from these sources (based on my own encoding experierences)
you end up with such artifacts that were not discerable in previous
color spaces.. ie, RGB. This is the nature of such codecs.. ie, divX
or XviD, etc. I am not knocking these codecs. Just bringing to light
what you are already finding out (finally) -- pfew.

I could go on and bore you further, but I won't

My suggestion for you here, would be to choose a different encoding
process. Since you are already finding artifacts, they may not be
removable. Try a different encoding, like CBR and *higher* bitrate.
See what that brings you. Probably nothing better, in the end.

Good luck,
-vhelp 3616

[Shadowmistress]

Wow, you guys are such pessimists! You know he's going to use that crappy divx anyway so why not offer him some helpfull advice?

Liverkick, the distortions you're seeing on the original avi are due to a too-low biterate used when the avi was encoded. There is nothing you can do to get back it's original quality now except to replace the divx with an uncompressed (or less compressed) source. Those bytes are lost for good.

The reason the distortions become more pronounced when converting to mpeg is probably because your ave biterate is too low and you're resizing the image. Even distortions will get resized as the encoder doesn't know what part of the image is desirable and what is not.

But if that's the only source you have to work with and you are intent on seeing this project through, I suggest you don't resize, up your ave biterate, and attempt some "restore" tactics from the restoration forum. Considering they're anime, you may have good luck using various filters in virtualdub and then frameserving to tmpgenc. You will get a better result than you have now, but it will not be the same as the original.

[liverkick]

Appreciate the replies guys...

But if that's the only source you have to work with and you are intent on seeing this project through, I suggest you don't resize, up your ave biterate, and attempt some "restore" tactics from the restoration forum. Considering they're anime, you may have good luck using various filters in virtualdub and then frameserving to tmpgenc. You will get a better result than you have now, but it will not be the same as the original.

Thanks for the tips Shadowmistress. It is unfortunately my only source at the moment. How high do you think I should go for the ave bitrate? I thought 6k ave would have made a difference but it didnt seem to improve much of anything to my naked eye to be honest.

jimmalenko, that was a silly mixup on my part I forgot to take out. I read the directions of a faq wrong when I was having trouble fitting to my display. I got the borders just right now.

[jimmalenko]

Try DivxToDVD. I don't think you'll be disappointed.

[Shadowmistress]

How high do you think I should go for the ave bitrate?

Dunno. I usually don't encode so high. But I'd suggest you up your maximum biterate at least to 12000.

Grab a biterate calculator and go as high as you can for average while still fitting it onto one disk.

[jimmalenko]

12000 ?


You're getting into "Player choking" territory there.

[manono]

To add insult to injury, you're destroying the AR with that AddBorders. And you don't add 0,0.5 to Lanczos. Try this for your 640x360 source for encoding to 4:3 (not 16:9, which will be different).

LanczosResize(672,336)
AddBorders(24,72,24,72)
ConvertToYUY2()

[Shadowmistress]

12000 ?

You're getting into "Player choking" territory there.

Not as an average but as a maximum. The theory was to have no ceiling on how high it can go when it needs it, just in case the mpeg conversion was causing any of the distortions. You have a better suggestion for a maximum?

[jimmalenko]

I know you said max

I wouldn't go any higher than 9000. You shouldn't need to, anyway.

[Shadowmistress]

Ok, go with 9000 then. Jim would know better than I would on this.

[FulciLives]

When converting MPEG-4 stuff to DVD you have to filter it.

I would try one of the following:

1.) VirtualDub MSU Deblocking Filter - CLICK HERE for the link.

2.) AviSynth Convolution3D Filter (has settings optimised for animation) - CLICK HERE for the link.

Either one (or both) should help with removing the artifacts.

Also must be sure to use a decent MPEG-2 DVD bitrate and resize correctly.

CLICK HERE for a bitrate calculator

As for the resizing ... use a program called FitCD

- John "FulciLives" Coleman

[jimmalenko]

DVD compliance says you gotta be under 9800 anyway.

There's also been a number of threads here that talk about players choking on high bitrates, and these people have re-encoded their sources to be under 8000 and the problem has gone away, so there's a bit of water behind the "player choking" theory.

The other thing as I said earlier is that there really shouldn't be a need to get anywhere near these high bitrates unless the source is very noisy, or is extremely high-motion.

Maybe even try a CQ encode ?

[liverkick]

2.) AviSynth Convolution3D Filter (has settings optimised for animation) - CLICK HERE for the link.

Either one (or both) should help with removing the artifacts.

Thanks for the links. Im having a problem getting AviSynth to recognize the Convolution3D filter, Im not familiar with adding filters to synth so maybe (probably) Im doing something wrong? I just unpacked the DLL into avisynth's plugins folder and assumed it would work, but Im getting script error in vdubmod and wmp "Script Error: There is no function named Convolution3D".

[manono]

Hi-

If for some reason the .dll doesn't load automatically, just add a LoadPlugin line to the script, up near the top:

LoadPlugin("C:\Path\To\Convolution3D.dll")

If that doesn't work, let's see your whole script.