Is there a way to make the constant quality mode and quality settings easier to use? I have noticed a large bitrate range amongst my encodes at a set quality thus making it difficult (time consuming) to figure out what percentage to choose. For example, setting the quality to 70% will give bitrates ranging from 2500 to 7000 kbs amongst my DVDs. I want to have the benefits of constant quality/CRF and keep my bitrates around 3000 kbs +/- 500 kbs, but find it a pain to figure out what percentage will give me that. Additionally, the difference between 68% and 70% can sometimes be close to 1000 kbs.
How do you decide what percentage to use without trial and error? Is there a way I can determine the bitrate of the source and calculate what quality setting I should pick to get close to my desired bitrate?
Also, when watching CRF encodes in Quick Time I notice that the bitrate does not increase/decrease depending on the motion in a scene. Should I be able to see it fluctuate in Quick Time? Thanks.
Easy to use Constant Quality
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Re: Easy to use Constant Quality
You don't.cbud wrote:Is there a way to make the constant quality mode and quality settings easier to use? I have noticed a large bitrate range amongst my encodes at a set quality thus making it difficult (time consuming) to figure out what percentage to choose. For example, setting the quality to 70% will give bitrates ranging from 2500 to 7000 kbs amongst my DVDs. I want to have the benefits of constant quality/CRF and keep my bitrates around 3000 kbs +/- 500 kbs, but find it a pain to figure out what percentage will give me that. Additionally, the difference between 68% and 70% can sometimes be close to 1000 kbs.
How do you decide what percentage to use without trial and error?
That's the whole point of constant quality.
The bitrate needed to reach a given quality varies by DVD. Varies frame by frame, really.
Of course the bitrate varies largely between 68 and 70. There are logarithms involved, you know.
If you care about keeping a bitrate at a certain spot, you should be using 2-pass ABR, not CRF.
In the case you seriously want to pursue this, see this doom9 thread for the math involved in estimating a bitrate from a crf value: http://forum.doom9.org/showthread.php?t=116773
Dunno about the QT thing. The variance happens frame-by-frame, so it probably just gets smoothed out by whatever formula QT uses to arrive at the current bitrate.