Xvid Pixellating

[MaggIvy]

For some reason my Xvid would pixellate big time in scenes with a lot of action and details, but only in little sections, not the whole clip.

I'm using the latest in Nic's build. And i used two pass.

Is there any reason why? I looked around and found nothing.

[foxyshadis]

Too-low bitrate or an incorrect matrix or both. MPEG especially causes lots of ringing (the noise sometimes called mosquito or pixelation) and blocking at low bitrates, but even H263 will at low bitrates. That's just the way it goes if you don't have enough space. You can try filtering away some noise/details or raising the bitrate.

Depending on your bitrate, definitely try using one of these matrices: http://forum.doom9.org/showthread.php?t=83125

[MaggIvy]

Strange but i have 250 gigs of free space, and the settings are a their max. The only thing i changed was the Q1 frame because i was getting major oversizing problems (which is not working, I'm messing around with the solutions posted in the sticky). I just read in that thread that it might be the trellis quantinization, so i'll disable it and see what i get. Also what is trellis quantinization?

[stax76]

This should give you a hint:

http://forum.doom9.org/showthread.php?p=804178#post804178

I recommend to use always post processing. Since you encode to the hard drive it's better to use single pass with fixed quantizer, two pass is mainly to hit a exact file size like 1/3 DVD or 700 MB (CD).

[MaggIvy]

So post processing is encoding before compressing it?
I pre-compressed it with huffy then tried to bring the size down by using two pass...I need the best quality possible because i might need it for editing.

[foxyshadis]

Trellis is fixed in the latest versions (http://www.koepi.org/XviD-1.2.-127-25022006.exe), and only affected high bitrate matrices using Q1; since you aren't using Q1 (a good idea) that wouldn't affect you. Either way, trellis basically performs several tests to decrease size without affecting quality, for a speed hit.

What bitrate are you trying to hit, anyway?

Oh, for editing? You'll want EQM EHR matrix, or UHR for smaller size with minimal loss, with 1 or no b-frames, and probably a short key-frame interval. Use q2; it'll come out huge, but compressing for small size and for editing are entirely different, and you simply can't have both.

[MaggIvy]

I'm trying to get a fixed size in kb. But in bitrate it would be 1046. Its for a high quality 5 minute 6 second video.

[MaggIvy]

I still wonder if there is a fix for my oversizing problem, i've tried everything....

[foxyshadis]

You're not going to get editing quality at 1Mbps if it's anywhere near DVD resolution. Try V3LR or ULR to get it looking less noisy. And how about making one for editing and one for burning? If it's a music video you'll probably need between 1200-2000 for high quality, depending on how crazy it is. Why do you need fixed size for 5 minutes?

Since you haven't explained the nature of your oversize problem, it's hard to help with that.

[MaggIvy]

Well it starts that by with its first compression it runs really well, its a good size, but if its too big and when i go to size it down on the second pass, it blows up to 500 plus MB. When the original was like 15 MB. Its dvd quality but i resized it to 640 by 480. I need it to be a fixed size because not only me someone else i have to send it to (via internet) will be using it. Its video game footage.

[foxyshadis]

Post a screenshot of your main second pass panel, or just a dump of the registry settings.

[MaggIvy]

I'm not sure if this is it but here's the shot:

http://i4.photobucket.com/albums/y148/MaggIvy/untitled3.jpg

[foxyshadis]

I actually meant the bitrate settings. What I think it might be, is you might be putting the final size (in K) in where xvid expects a bitrate. It has two modes, target bitrate and size. If it's set to bitrate when you expect size, of course it'll come out wildly oversized, or if it's set to size and not changed (the default is 560MB, fancy that).

Try also loading defaults, then go back in and make your changes again, in case an old version's screwing something up.

[MaggIvy]

I'll do that, should i keep the b frames?

[Selur]

about the oversize: using more restrictive overflow treatment settings should solve the problem.

[stax76]

Storing on a hard drive and using two pass don't make sense, does it?

[Chainmax]

Trellis is fixed in the latest versions (http://www.koepi.org/XviD-1.2.-127-25022006.exe)
...

Does this version have any side effects encoding or decoding-wise?

[foxyshadis]

Well, it multithreads and it's a little more efficient at the bottom of the quality scale. Otherwise I really haven't noticed any changes (but I don't pay close attention, like I do with x264). I have no reason to believe the rest of the changelog is faked, though. :p

[MaggIvy]

Storing on a hard drive and using two pass don't make sense, does it?

For me it does because I need to save all the space i can.

[stax76]

For me it does because I need to save all the space i can.

There is no gain between multipass and quality mode, the quantization is different but not more efficient. XviD at quantizer 3 gives you a balanced quality/compression ratio if you use a good post processesor like DivX.

[MaggIvy]

This one doesn't have quality mode...if there is one i'd like to know. I used to use the 1 pass quality on the very old nic's xvid and i always got good results. IS there really one in the newest Xvid?

[Didée]

"Quality Mode" is just the same as fixed quantizer.

Q100 == q2 / Q0 == q31

[MaggIvy]

Thanks I'll try that.

Just one question,

What do you mean by:

Q100 == quant-2 / Q0 == quant-31

[Didée]

Quality = 100% is the same as fixed quantizer 2.

Quality = 0% is the same as fixed quantizer 31.

Quality = x% is the same as fixed quantizer (100-x)/100*30 + 2

BS ... same as 2 + 29/100*(100-x)

[MaggIvy]

Hmm i tried it at fixed quantizer at the max setting and i get this nasty pixellated result. Can i get the same results with the bitrate 1 pass instead?

[DarkZell666]

Hmm i tried it at fixed quantizer at the max setting and i get this nasty pixellated result. Can i get the same results with the bitrate 1 pass instead?

Simply try using the max bitrate available and setting MinQuant to 2 and MaxQuant to something like 3 or 4 (for I, P and B frames). The video might come out smaller than ((bitrate / 8) * length_in_seconds))KB since if it doesn't need all that bitrate it won't use it :)

[MaggIvy]

Thank you.

Problem solved, for now i think.

[Mug Funky]

Hmm i tried it at fixed quantizer at the max setting and i get this nasty pixellated result. Can i get the same results with the bitrate 1 pass instead?

you mean quant 31? best not do that. quantizer is inverse to quality. the higher the quantizer the lower the quality. so quantizer 2 is good where 30 is bad.