tweaking settings for more "filmlike" quality

[phædrus]

I started using GKnot for DivX encoding for the first time this week. Previously I've been encoding to SVCD with DVD2SVCD. Just generally, without doing a lot of tweaking -- using the presets -- I find that MPEG-2 videos tend to look more filmlike. They're a bit fuzzier with the noise taking on more the appearance of film grain. On the DivX videos I've made, the edges tend to be sharper, but with weird shifting of noise going on in the background, particularly on large swaths of sky or walls or floors or anything that doesn't have much texture to it. And sometimes more "mosquitoes" around foreground objects that move with the object against the background.

Using the Lanczos resize, which I think is default on my version of GKnot, only seems to accentuate this tendency in DivX encodes. (I happen to be using the 5.0.2 codec.) Using bilinear resize was said to make movies more compressible, and does soften the edges a bit for a more filmlike appearance.

Are there any tweaks one can do to the codec settings (or any other tricks) to give a more filmlike appearance -- i.e. lessen the likelihood of a "cloud of mosquitoes" following an object around, or the odd noise behaviour in broad textureless areas? In other words, how would I make DivX appear more like MPEG-2 (though perhaps a bit more detailed -- but not to excess)? I'm willing to sacrifice a bit of sharpness for more uniformity and fewer odd-looking artifacts.

If any of you can give me some suggestions, I can try them out.

[manono]

Hi-

These are problems common to MPEG-4 encoding, but, in my opinion, DivX is worse about it than is XviD. The best thing you can do is to throw more bits at it-lower the average quant. A compression test can help you determine how it'll compress, and if you should raise the file size/lower the resolution or not.

One thing you can do is to add grain/noise during playback. This subject has been discussed extensively, mostly in the XviD Forum. Here's a current discussion:

http://forum.doom9.org/showthread.php?s=&threadid=76971

[ukb007]

If not, try it. I find the quality unbelievable.

Regards.

[phædrus]

I don't doubt that XviD is better in many respects. I already have a large number of DivX encodes, and have no plan to change formats. Picture quality is only one consideration when choosing a format.

I've had enough problems dealing with DivX, and since starting to use GKnot I've had problems just getting new encodes to play properly on the same media players I was using before. (Seems to be related partly to the type of audio track used.) Maybe I should have started with XviD in the beginning, but I didn't.

As for the general effects I was complaining about, I think manono is right, that they are to some extent a feature of MPEG-4 codecs in general, and the DivX codec specifically. I'll probably just work around it by using a higher bitrate. I think I'm getting more tolerant of those artifacts over time, anyway. :-)

[jggimi]

The resizing method chosen will have a large impact on the finished image.

Lanczos may be too sharp a resizer for your personal taste. Softer resizing may change the image more to your liking. Sharp bicubic is softer than Lanczos, and Neutral Bicubic is softer still.

(See Doom9's codec comparisons -- he used Neutral Bicubic resizing in every test.)

You may "preview" in Gknot so that you do not need to encode to see the differences in resizing filter. This will "play" the AviSynth script (.avs file) in Windows Media Player as uncompressed video.

Note also that Gknot adds an Undot() filter into its generated script. You may remove it or comment it out, which may provide a somewhat grainier look to the resulting images.