Getting the best bitrates.
No Matter what method your using, if you plan on encoding a dvd-9 to a dvd-5 and keeping all the extras,your going to have to work out some bitrates to put your movies at. Now what most people do is that they choose say 1750 for all the extras and then wok out what left for the main movie. This is madness, pure wastefull! Two sound trailers, equal in length, I gave them both a bitrate of 1750. The first loooked deadly, infact it would have looked equally deadly at 1400, so that was a waste of bitrate. However even at 1750 the other trailer looked crap, it needed a bitrate of 2000+!!!! Now see what going on???
My idea is to encode all the extras using CCEs one pass method at a set q of say.. 30. Now lets say the extras come out as follows:
Now we work out the percentage each needs of the dvd, a quick calculation and wella!
Then you can use this to work out the bitrate, and each part will ge the right ammount of bitrate to optain optimal quailty.
The above example only includes small files but it woks the same if say E was the main movie and it needed 50% of the dvd.
Anyway, as some people reading this will already be thinking, this means the extras and main movie will get the same quailty. Most coders like to work it out in such a way that the main movie gets a good bit more attention then the extras. So I have done a load of test encodes and found some "constant results" that CCE will always give and from this I worked out two different sets of Q's which give quailty in different ratios. Heres the two here:
A Q of 20 for the main movie and a q of 40 for the extras give a Quailty ratio of 3:2 (1.5:1)
A Q of 20 for the main movie and a q of 60 for the extras give a Quailty ratio of 7:3 (2.3:1)
Now what exactly does this mean??? Well simply enough If you used Q number 2 than the main movie will get 2.3 more space then it would normally. Or if you used Q number 1 then you the main movie will get 1.5 times the space it would normally get.
In cases where the bitrate is plentyfull then simply use the first ratio. However if you have a DVD where there are a lot of extras and you need a little more bitrate for the main movie than you may want to try Q number 2.
Any posts appreciated, feedback always welcome.
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