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Old 12 Feb 2004, 09:27 AM   #1
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Default Weight???

I tried using the forum serach, but came up with a big fat zero, all i would like to know is what the hell does weight mean in the XviD 1.0 RC1 in the zone options, thanks.

P.S does it mean how powerful the encoding will be or something.
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Old 12 Feb 2004, 09:44 AM   #2
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maybe this quote might help:


Quote:
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 :

code:

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.

code:

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 :

code:

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 :

code:

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


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.
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Old 12 Feb 2004, 10:34 AM   #3
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Thanks, at least i have an idea now of what they are for, unlike before.
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