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  1. Member
    Join Date
    Jun 2007
    Location
    Canada
    Search Comp PM
    Hi

    I went to http://www.x264bluray.com/home/720p-encoding

    re: Authoring a professional Blu-ray Disc with x264

    all the examples use two pass encoding, e.g.:

    720p23.976 / 720p24

    x264 --bitrate XXXXX --preset veryslow --tune film --bluray-compat --vbv-maxrate 40000 --vbv-bufsize 30000 --level 4.1 --keyint 24 --open-gop --slices 4 --colorprim "bt709" --transfer "bt709" --colormatrix "bt709" --sar 1:1 --pass 1 -o out.264 input.file

    x264 --bitrate XXXXX --preset veryslow --tune film --bluray-compat --vbv-maxrate 40000 --vbv-bufsize 30000 --level 4.1 --keyint 24 --open-gop --slices 4 --colorprim "bt709" --transfer "bt709" --colormatrix "bt709" --sar 1:1 --pass 2 -o out.264 input.file


    and from a short thread at doom9:

    Could someone please check the following and let me know if it should produce a blu ray compliant encode?

    --demuxer ffms --fps 24000/1001 --force-cfr --crf 18 --preset slow --bluray-compat --level 4.1 --tune film --keyint 24 --open-gop --pic-struct --slices 4 --sar 1:1 --partitions all --vbv-maxrate 35000 --vbv-bufsize 30000 --colorprim "bt709" --transfer "bt709" --colormatrix "bt709"

    [response]
    If the resolution is right and you output to .264 it should.

    My question then: if I use a crf value that keeps the max bitrate under 38000 are there any disadvantages compared to using a two-pass encode?


    TIA
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  2. The main disadvantage is you don' t know what bitrate (filesize) you end up with . It won't violate vbv restrictions (won't go over), but it can undersize

    If you are using crf encoding with vbv, I would use lower crf value . On some sources, you might find it terribly undersized with very low bitrate

    If you did encode that way and ended up with "x" bitrate, and did a 2pass encode using "x" bitrate, but other settings the same - the quality will be very very similar (there will be very slight differences)
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  3. Member
    Join Date
    Jun 2007
    Location
    Canada
    Search Comp PM
    Thanks pdr - that's what I was thinking re not knowing the final bitrate - I suppose I could use variations of SelectRangeEvery and experiment a bit with crf values . . .
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  4. IMO , that's a huge problem when you're trying to author to a fixed capacity disc optimally, with menus & multiple streams.

    IMO, the SelectRangeEvery or derivative functions are very poor predictors of final video bitrate. It's difficult to sample correctly. It might be within 5-25% of the final encode, but that's hardly accurate enough
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