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  1. I'm using MEncoder to encode a DVD to H.264 with 2-pass x264, but I don't understand why the first pass is going much faster than the second pass, I mean, in the first pass, x264 encodes about 45 fames in one second, and in the second pass it encodes 6 frames per second, wich is normal for the preset "slower" that I chose, and it should encode 6 fps in pass 1 as well.
    Last edited by codemaster; 21st Sep 2011 at 15:21.
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  2. By default, 1st pass uses fast settings with 2pass encoding

    If you want to enable slow first pass , use --slow-firstpass . I'm not sure what the syntax is in mencoder

    http://mewiki.project357.com/wiki/X264_Settings#slow-firstpass
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  3. @ poisondeathray: true

    I found out from MEncoder's manual that, the parameter slow_firstpass
    disables the following faster options with pass=1: no_8x8dct me=dia partitions=none ref=1 subq={2 if >2 else unchanged} trellis=0 fast_pskip. These settings significantly improve encoding speed while having little or no impact on the quality of the final pass.
    This option is implied with preset=placebo.
    But If I don't use slow_firstpass I think the bit allocation decisions will not be as accurate as possible in the second pass, or final pass, is this true ?

    Syntax is specified in the same manual.
    Last edited by codemaster; 21st Sep 2011 at 18:58.
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  4. Makes almost no difference

    Compare it yourself. Do encodes with it and without it . IMO it's not worth the speed penalty. I've compared 100's
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  5. Why even bother with bitrate based encoding? Just use a constant quality mode. The file will come out with exactly the right bitrate for the quality you ask for -- in a single pass. Try CRF 18. Bitrate based encoding is only useful when you need a file of a particular size. Like when putting a 2 hour movie on a 700 MB CD.
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  6. @ jagabo: true; I didn't knew about CRF until now
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