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Old 4th September 2012, 17:04   #1  |  Link
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Join Date: Jun 2012
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Estimating/Predicting CRF bitrate or file size

As the title says, is it possible to estimate beforehand the expected bitrate or file size of a given encode at a given CRF factor??
The reason I ask is because I would like to estimate the output size of an encode at CRF 20 for example, then actually encode the video in a size based 2-pass mode. I am not trying to keep the encodes below a certain file size, but rather, trying to maximize quality at the best file size possible. So encoding in 2-pass without a quality reference would be flying blindly. That's why I rely on a constant quality CRF pass to get the needed bitrate for a 2-pass encode to achieve a certain level of quality.
But as you can imagine, this is a very slow and time/resources consuming approach. This is why I'm looking for some kind of estimation method or quick virtual CRF pass that estimates the bitrate quickly without actually encoding the video.


P.S: Please, let the CRF vs 2-pass debate for another thread. To me, based on the testing that I've done, 2-pass produces slightly better (but pretty noticeable) quality than CRF at a given bitrate.
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