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Originally Posted by jptheripper
wrong wrong wrong
only the average bitrate is set on the cell, but within the cell the vbr is done by scene detection in the encoder. Hence high action will still recieve high bitrate
it has been shown many times that the difference in bitrate done this way versus using the whole movie at once is insignificant.
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Nope Nope Nope, the encoder uses VBR but the DEFAULT average is set cell by cell. So if you have a cell with 90% average of 2000 and 10% avergae 6000 in one cell, the avergae would be 9*2000+1*6000/10= 2400 average.
Having this value as a target value, the encoder will do encoding in VBR but it will be totally at the expense of the 6000 part, which will degrade in quality and probably have blocks when played back......
Now make it a distribution of 95% to 5% and it's even worse. The encoder has to reach the 6000 from 2400 average, which won't be possible in this way.
I have seen this happening in the LORD OF THE RINGS movies.
The bitrate is enough for the more static scenes, but too little for high action/high movement scenes and these have a blocky appearance as a result. That's because the encoder has not enough 'headroom' to encode them at the lowest possible bitrate without going the get the blocky picture.
I would like to steal some bits form the more static scenes and apply them to the scenes that get blocky. As the movie is 95% unblocked and just 5% of the movie has blocky pictures this should be possible. But with the current way DVD-RB assigns segments and average bitrates it's impossible to get this done. Yep manually change bitrate assignments.............
That's why cell based distribution is in essence not correct. It should be divided into bitrate-alike segments in stead of cell-based segments....
If you can set a kind of treshhold and and other parameter values to prevent the formation of too many segments, this would be an ideal solution.......
The spitting is then really 'lot alike same bitrate' based and not cell based.
In this case the following would happen:
----------- cell 1 -------------|------------ cell 2 -----------------------|
--------- low action--------|+++++++ high action +++++|----- low action-
--- SEGMENT 1 AVERAGE X | ------- SEGMENT 2 AVR. Y | - SEGMENT 3--
and not:
-------- SEGMENT 1 AVR Z1----|-------- SEGMENT 2 AVR Z2-------------|
as now happens in DVD-RB.