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1st January 2009, 05:20 | #1 | Link |
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Pure quality, CRF or 2 pass?
If I want the highest quality encodes without time limit, is CRF better or 2 pass? Suppose I encode a video using CRF x, and it output a video that is 800MB, now I use 2 pass, and specify the size to 800, which way of encoding would provide higher quality?
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1st January 2009, 05:37 | #6 | Link |
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Their goals are different, CRF permit you to reach a certain "quality" (I do my encode with CRF-20, CRF-18 is considered as transparent) but ignoring what will be the final size, while bitrate permit you to reach a certain size (for the quality, you don't have a clue before seeing the result)
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1st January 2009, 05:37 | #7 | Link |
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CRF, 1pass, and 2pass all use the same bit distribution algorithm. 2-pass tries to approximate CRF by using the information from the first pass to decide on a constant quality factor. 1-pass tries to approximate CRF by guessing a quality factor over time and varying it to reach the target bitrate.
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1st January 2009, 06:54 | #11 | Link | |
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My preference is to use CRF 16 if I am not concerned about filesize and to use 2 pass to acheive a given size output.
here are lnks explaining options. http://www.digital-digest.com/articl...ons_page1.html http://www.mplayerhq.hu/DOCS/HTML/en...feat-x264.html I really haven't seemed to need to understand vbv(Video Buffer Verifier) - maybe I should, this is what I have found. Good Link http://rob.opendot.cl/index.php/usef...es-and-levels/ Quote:
Last edited by flebber; 1st January 2009 at 07:04. |
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1st January 2009, 19:37 | #16 | Link | |
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Quote:
In short: If you are targeting for a certain level quality and you don't care about filesize, then find the highest possible CRF value that still satisfies your eyes and use that CRF value for all your encodes. And if you are targeting for best possible quality for a restricted filesize (e.g. 700 MB for a CD-R or 4,7 GB for a DVD+R) then use 2-Pass mode.
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1st January 2009, 22:20 | #17 | Link | |
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Quote:
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1st January 2009, 22:22 | #18 | Link | |
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But as far as I know they do not produce the exact same output at the same filesize. However the results will be very very close. I doubt you will be able to spot the difference... Quality-wise the 2-Pass mode is guesswork. At least if you did not do any tests in advance to find a reasonable bitrate. But size-wise it's exact. In contrast to CRF, which produces an unpredictable size (but predicable quality - roughly).
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4th January 2009, 02:56 | #20 | Link |
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No, the crf value is related to the quantisers used. A higher value uses higher quantisers which produces lower quality, a lower crf value produces higher quality.
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