XviD - Settings, Colorspaces question

[redfordxx]

Hi,
can anyone tell me,
1. whether and what difference makes .avs input to XviD in RGB32, YUY2 or YV12? (Suppose now there is same informantion in the input --- afaik YV12 has lowest quality, then all should be cca same as YV12)

2. Is somewhere described, which parameters in XviD settings are related to 1stpass and which not? In other words, which can/cannot be changed in the 2ndpass based on the same stats file?

3. Is mod8 video size sufficient? I read somewhere about mod16 --- is that outdated?

Tnx R.

[*.mp4 guy]

1st off USE SEARCH

ok, now to the questions.

1. Xvid compress all video in the yv12 colorspace. (so color space as far as your concerned is irelevant)

2. Avoid changing settings between passes for best quality, especialy qpel. bitrate isn't used in the firstpass so you can change that as much as you want.

3. quantisization is 8X8, so your video should be atleast mod8, macroblocks are 16X16 so its good if your video is also mod16.

4.USE SEARCH

[redfordxx]

Originally posted by *.mp4 guy
1st off USE SEARCH
I did and will do. I found many things but not all...

1. Xvid compress all video in the yv12 colorspace. (so color space as far as your concerned is irelevant)
Before you answered I tested it. One YV12 source i converted to RGB32 (with avs) and encoded. Compared to this moreover ConvertedBackToYUY2 the 1pass was cca 1% bigger. So there is some difference... Maybe it is XviD internal color converter? It is better to feed XviD always with YV12?

its good if your video is also mod16. somehow noticable difference...?

[Manao]

Just a few precisions :
- The mpeg4 part2 allows for any resolution at least mod2, because the input picture can be padded ( meaning expanded at its borders ) in order to be mod16. That process happens as soon as one of the vertical or horizontal resolution isn't mod16.
- That process means that the encoded picture in case of non mod16 input is bigger that the displayed picture, hence there's an efficiency loss.
- Whatever you give XviD, it will convert it to YV12. So it's up to you to choose whether to give it what it will need in the end or not. The main advantage of giving YV12 is of course when your all processing chain is in YV12, but that's not the case for you.