Bitrate (1st and 2n Pass ) slow Down x264

  • Hans-Arafat

    Hans-Arafat - 2010-04-12

    Hi :D (sorry for my Bad English, i´m from Germany ^^ )

    First :) You did a great Job with x264 for vfw !

    I use your x264 vfw builds for a long Time, so i´m no complettely Noob.

    Bud today i found some very Strange Bug (it must be a Bug, because it´s
    complett unlogical)

    Info -> First: -> I Reset everything to Default, and it was the same Problem.
    Vfw Version -> Build Date 29 Jul 2009 - 10:35:33
    libx core 68 r1195bm 5d97a9b

    Input WMV2/8 Crap 720x480 29,97fps ntsc, 1Pass, 5500kbits (yeah Crap Settings
    and Codec, bud
    it´s from a XXX Website xD )

    Ok i load that Clip with Avisynth in VDub 1.7.x

    Fast Recompress, Audio disabled.

    First Pass Fast - Bitrate 2000kbits -> Speed ~ 32fps | Peak 35,70
    Second - 2000kbits -> Speed ~ 11fps | peak 12.59

    Now with 1000kbits
    First Pass Fast - Bitrate 1000kbits -> Speed ~ 42fps | Peak 46,54
    Second - 1000kbits -> Speed ~ 16fps | peak 17.34

    3)Now 1 kbits for the First Pass
    First Pass Fast - Bitrate 1 kbits -> Speed ~ 77fps | Peak 83,24
    And 2000 for the Second
    Second - 2000kbits -> Speed ~ 11fps | peak 12.59

    The Result from Case 1 and 3 are identical, bud the Speed not.

    This is absolute no logical. ( if i use xvid, it makes no difference, the
    speed is every
    Time the same in First or Second pass, Bitrate dont slow down or speed up)

    First Pass is only for Analyzing (like in xvid, in xvid the Slidebar Gadget
    must be disabled) bud the kbits decrease the Speed, and in the Second Pass
    it´s the Same !

    Logical -> More Kbits -> Not many Work for the Codec, to create a good
    Picture.-> less work -> Speed Up
    Unlogical -> More Kbits -> Not many Work for the Codec, to create a good
    Picture.-> less work -> Slow Down ?

    With this Bug x264 is totaly useless, it´s a waste of Time to find Settings
    that are
    Good and Fast.

    I hope you can fix this Problem, it´s very sad that such a Great Work got such
    a Big Bug.

  • BugMaster

    BugMaster - 2010-04-12

    First of all this not the bug. Yes, first pass is only for analyzing but
    chosen bitrate influence on the generated stats file and so Case 1 and Case 3
    wouldn't give identical results because they have different stats files. It is
    recommended to keep bitrate of first pass and next passes close to each other
    because this would generate more actual stats file for final pass and so
    increase quality. As to why higher bitrate is slower than lower bitrate is
    because work of encoder increase with increasing of bitrate. Codec need to
    compress more data through CABAC or CAVLC entropy encoder while other work
    (ME, analyze and etc) is kept near the same.

  • Hans-Arafat

    Hans-Arafat - 2010-04-13

    Thanks for you awnser thumbsup

    I compared Case 1 and 3, and cant find significant differences, just the
    For me is Case 3 the bether way.

    I´m a try many variations and Settings, and now i must see all Settings that i
    try (to find a good balance
    between Speed and Quality) and save (as VDub Processing Settings) in the Past,
    are complette useless -.-

    I Ripp Down many Stuff with Batch Processing(i dont like Batch Files or
    FFCoder) in that way.

    I Create VDub Processing File, with all Settings that i need, and use this 3

    Multiple Avs Maker+ VDub Batchbuilder (use VDub Processing File) +Multiple Mkv
    Merger (i write all 3 for Private use)

    So i try to find balanced Fix Settings.

    Same Settings, nevermind how the input source is ** just different Bitrates
    for different Resolitions and more a mimumum 25 from 25fps in the Second Pass.

    ** H + W * 1.45 (worked good for XVid and x264)
    The Most Stuff that i Rippdown got the same Quality, same Camera, same
    Locations, was used xD so fixed
    Settings work good.

    Bud now i got a realy big Problem, XVid is to Slow in High Resolutions, and
    x264 Speed is seems to 60% not Settings based (it look like that) it´s Bitrate
    based :( and i cant be shure, that i found the best Balance between Speed and
    Quality, in the needed Resolution.

    Maybe you can add a GadgetToolTip for the Slidebar, that the Speed Change with
    the Bitrate.


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