Resize Divx/Xvid For Portable With VDub: Artifacts/blur

[gordonliu]

I am trying to downsize a 592x320 xvid avi to something close to 320x240 (maintain A/R).

Using VDub (1.8.8) and the newest xvid codec (standalone, not ffmpeg/pack)

full processing mode

Xvid settings (configure): no change to settings.

Filter: resize

resize settings: precise bilinear, 444x240.


sound (ac3) taken care of with besweet, VBR, no sync issues or anything. just added this for completeness, but no issue whatsoever.


the PROBLEM is this:


when panning past dense vertical and horizontal lines, instead of getting jagged edges (an interlacing problem), the vertical lines/square shapes BLUR in a fluid motion, almost as if certain portions of the screen move seperate from the rest.

specifically: when panning slowly past the milk isle in a super market (lots of milk containers stacked above/next to each other) the milk boxes blur visibly in this manner.

when I say blur, i mean that this part of the screen actually moves around fluidly.

I also get lots of blocky artifacts in dark scenes, but I think that may be expected from a rip.


MY GUESSES:

1) convert to uncompressed THEN compress to xvid

2) use 2pass-1stpass or 2pass-2ndpass encoding mode




I dont know of any better app than vdub, or at least I do not know of one that will produce a more accurate product.





I searched, and I have found plenty of discussion of interlacing issues, bicubic vs bilinear, how to do the whole process, etc.

I could not find anything satisfactory related to my specific problem.


any help would be appreciated. and if missed a previous thread on the same subject, feel free to scream and yell at me.

[poisondeathray]

If you used default xvid settings, the quantizer would be 4. Try lower like 3 or 2, but the filesize will increase. You can also set VHQ to 4 instead of 1, but this will have less of an effect that the quantizer . Your device probably has compatibility limitations on bitrate and some other xvid settings (e.g. QPEL, GMC)

Lanczos resize will give sharper results than either bilinear or bicubic

If you did it through an avisynth script, feeding into vdub, you could use "fast recompress" mode instead of "full processing mode", and not suffer the quality loss from the colorspace conversion caused by vdub

You might also try the VAQ patched xvid build, which helps to redistribute bits to dark and flat areas and should help with the blocky pixellation that you describe

All these little tips will only help a bit: i.e Don't expect miracles; you are re-encoding from a (probably low quality) rip to an even lower resolution. If you started from the blu-ray or at least DVD you would get semi-decent results

[jagabo]

Post a few seconds of your source and your xvid encode.

[themaster1]

why downsize to 320x240 ??

592/320 = 1.85 # 320/240 = 1.33 ( 4/3)

For the xvid settings forget the gmc, adaptative quant & quarter pixel options, set quantizer values as follow: minimum 2 maximum 16 31 is WAY too high for my liking and indeed pick a reasonable bitrate the larger the frame size, the higher the bitrate witha minimum around 900 but it's too low for my liking around 1200 is generally best for a frame size of 640x480 or lower

[gordonliu]

thanks a lot. I really love this site.

NOTE: I am using an archos AV700. absolutely excellent device, despite its ridiculous lack of ac3 or aac support. not only is it a wonderful player, but it doubles as a great battery powered 100 gig hd.

let me explain my reasoning here:

the player can play anything I have thrown at it, but it has a hardware max 320x240 res. If I can save 500 mbs or more per file, I can double or triple the amount of movies I can hold on it.

themaster1:

I just meant something NEAR that resolution. yes, I am going to keep the AR. I was thinking 444x240, doesnt really matter though. I figure 444x240 is the best, as it will at least maximize both dimensions.


jagabo:

not so sure if that is a good idea. I will check the rules before I post that.


poisondeathray:

Okay, to sumarize your suggestions + the rest of the settings

fast recompress
change quantizer to 2 or 3 and/or VHQ setting set to 4 instead of 1

now, in terms of xvid-vaq, is this a REPLACEMENT codec? is it BETTER than the normal xvid codec?


I am not going to call myself a n00b, but I am certainly not even an "amateur" at this type of stuff. as a matter of necessity, I have tinkered with Divx, DVD, and audio files for several years, but I am not up to date with anything.

I will try your suggestions and get back to you with the results.

I have a crappy 1.83 ghz core duo t2400 (laptop) processor, so it takes about 40 minutes for the full film.

[citanool]

If you want something simple, try AutoGK or AviRecomp. VAQ w/ESS option enabled in AutoGK is producing better results for me than without.

[jagabo]

jagabo:

not so sure if that is a good idea. I will check the rules before I post that.

Short clips are "fair use". At least post a few before and after images that show the problem.

poisondeathray:

Okay, to sumarize your suggestions + the rest of the settings

fast recompress
change quantizer to 2 or 3 and/or VHQ setting set to 4 instead of 1

Low quantizers may give you bitrate spikes that are too high for your player. Run some tests.

now, in terms of xvid-vaq, is this a REPLACEMENT codec? is it BETTER than the normal xvid codec?

Yes, the VAQ version replaces the older version. If you don't like what VAQ does you can disable the option. With constant quality encoding VAQ will give you smaller files. With CBR or 2-pass VBR encoding you should get better overall quality at the same bitrate.