Zones in Aloha

[Roman Helmet]

Well, I just got the new Aloha, and I am confused about all this zone business. I can't figure it out. I think it may have something to do with my file sizes ending up much larger than before. Okay, so, what are these new zone settings, what do they do, and why are they here now all of a sudden, and what are some recommended setting for them.

[Manao]

These zones are a more powerful version of the credit ranges of previous versions.

How are they working ?

Well, let's take an example. You have a 150000 frames long movie, which credits from the 140000th frame to the end. You want to encode the credits at quantizer 16.You'll configure your zones like this :Frame # | Weight ( Q ) | Modifiers
0 | 1.00 |
140000 | ( 16.00 ) |Now, if you want to encode the credit at 20% of the bitrate of the rest of the movie, you'll use weight instead of quantizers.Frame # | Weight ( Q ) | Modifiers
0 | 1.00 |
140000 | 0.20 |You may also have a beginning credit, from the 1000th to the 5000th one, so your zones will be :Frame # | Weight ( Q ) | Modifiers
0 | 1.00 |
1000 | 0.20 |
5000 | 1.00 |
140000 | 0.20 |Ok, now the modifiers, what are they meaning, what are their use ?

- Force Keyframe : it will force the codec to insert a keyframe at the beginning of the zone. It can helps, for example, when your movie ends with a progressive transition between the movie itself and the credits, making the codec insert no keyframe at the beginning of the credit zone. ( I can't think of another use, but there must be some very interesting way to use this feature )
- Greyscale : your zone will be encode in greyscale ( all the chroma information will be discarded ). Useful for example with a black and white movie beginning with a colorized generic :Frame # | Weight ( Q ) | Modifiers
0 | 1.00 |
1000 | 1.00 | G
- Chroma optimizer : your zone will be prefiltered by the chroma optimizer ( which should lead to less red & blue blocks where these colors are saturated )
- BVOP sensitivity : allows you to change the number of B-Frames that XviD inserts ( not the maximum number of consecutive B-Frames, but rather the tendency for XviD to insert a B-Frame ). The higher the value, the more B-Frames you should get. It's useful in a case where there is a specific passage in the movie which requires very few B-frames inserted in order to be encoded at a good quality, while the rest of the movie is very tolerant to B-Frames use ( note: you could also have raised the weight value to 1.5 or 2 for this specific zone, in order to get better quality for it )

A final note : you have to define at least one zone ( beginning at 0th frame ), else the behavior of XviD will be rather erratic. And the zone as to be defined in the right order( the frame number has to increase at each new line of the window ), else XviD will also behave erraticly

[Joe Fenton]

One of the intended uses for forcing a key-frame was to make seeking to chapter start positions work. Just start a new zone at each chapter point and seeking to a chapter will be dead-on instead somewhere within 10 seconds like normal.

[Enrico Ng]

Thanks for the great explaination.
It would be nice if there was new or updated guide which went through and explained:
what each setting is?
What its suppose to do?
What affect it has on the quality?
and reccomended settings in general

[Blueseb]

Do I have to set 20% bitrate on both 1st & 2nd pass, or only on 2nd? in older version bitrate reduction was enabled only on th 2nd, but I still had to specify range in the 1st so I'm getting a little confused now.

[Edit]
I did a test by myself and setting bitrate reduction only on the 2nd pass seems not to work, in according with Manao post just below this :o

[Manao]

Blueseb : I would say in both passes( at least, that's what I did, and it worked fine twice ).

Enrico Ng : it's too early to make a guide. The features safely usable seems to be GMC, Treillis, Adaptive Quant, VHQ 4, ME 6, and chroma motion. I would avoid Cartoon Mode ( except for cartoons, of course ), and QPel ( but that's personnal ). The rest is completly tweakable, especially the settings for the b-frames, which really depends on personnal taste, the second pass's settings ( because it takes a long time to test : you have to compress an entire movie to test it correctly ) and the matrix used( I use HVS_good )

[Enrico Ng]

Originally posted by Manao
Enrico Ng : it's too early to make a guide. The features safely usable seems to be GMC, Treillis, Adaptive Quant, VHQ 4, ME 6, and chroma motion. I would avoid Cartoon Mode ( except for cartoons, of course ), and QPel ( but that's personnal ). The rest is completly tweakable, especially the settings for the b-frames, which really depends on personnal taste, the second pass's settings ( because it takes a long time to test : you have to compress an entire movie to test it correctly ) and the matrix used( I use HVS_good )

ok thanks, I've done some tests with those new features. I'm just not sure about the combinations

[Manao]

Everything works with everything. So if you don't mind to slow down your encode, pick all the options you want :)

[Enrico Ng]

Originally posted by Manao
Everything works with everything. So if you don't mind to slow down your encode, pick all the options you want :)

Oh I meant if one feature alone did not help much, but if there were a large difference if it were used with some other feature.

I'll keep testing. This newer version seems to be alittle faster.

[Yuuhi]

Maybe a dumb question but I still doen't understand...
I set a starting frame in the Zones settings with all the modifications I need, then XviD will use those parameters until the end of the film, so that inserting the frame for the very ending of the film is quite useless, is this correct?

[gldblade]

Correct.

[Yuuhi]

TNX a lot gldblade