2500 Bit Rate VS 70% Constant Quality

Discussion in 'Apple TV and Home Theater' started by Alx9876, Apr 26, 2008.

  1. Alx9876 macrumors 6502a


    Jan 26, 2008
    I encoded two of the same movies "Enemy at the Gate".

    Here's the settings I used for both movies:

    -Apple TV Preset
    -2-Pass Encoding
    -Turbo first Pass
    -Audio 192 Kbps or AAC + AC3

    Except One is -2500 Bit rate while the other is 70% Constant quality.

    Now the Constant quality movie file size is 2.20 gigs.

    The 2500 Bit rate is 2.80 gigs.

    I honestly cannot tell the difference between these two files when watching them and making side by side comparisons.

    Did any of you do this before and stuck with one over the other?

    I want to know what you all are doing.

    The 2500 might have better picture but I think it's just darker more than anything. Other than that they both look identical.
  2. err404 macrumors 68020

    Mar 4, 2007
    I mostly use CRF. It will manage the bit rate dynamically to provide all scenes with a consistent quality. The down side is that the bitrate is not predictable. While in this case you ended up with CRF being smaller, sometimes it will be much larger.
    Basically the movie you encoded, just didn't need 2500 for excellent quality.

    FYI - if you are working off of a bad source video (very grainy, blurry, or just old) you may be better off forcing a bitrate since CRF can add a lot to the file size by trying to reproduce the flaws.
  3. hotshotharry macrumors 6502

    Sep 6, 2007
    So on average which would be quicker atv preset with 2 pass, 2 pass on turbo, or crf @ 70%

    LOL any chance someone knows this already?
  4. dynaflash macrumors 68020

    Mar 27, 2003
  5. hotshotharry macrumors 6502

    Sep 6, 2007
    I would have to concur, looks like atv preset, crf 70 - 72 % is almost 1 for 1 on my 2ghz mini. and the picture looks great :)

    LOL my advice, use the atv preset as it avoids reinventing the wheel :)
  6. cohibadad macrumors 6502a


    Jul 21, 2007
    CRF + VFR seems to give the best quality for fast scenes and since all films seem to have at least one fast scene I have been using it for all my encodes lately.
  7. err404 macrumors 68020

    Mar 4, 2007
    I may be mistaken, but does HB have issues with VFR occasionally resulting in corrupt I-Frames? I have never needed this setting since I can keep the same frame rate for both my source and encodes (24fps).
    I would recommend avoiding VFR unless you know the source frame rate differs from your encode.
  8. NightStorm macrumors 68000

    Jan 26, 2006
    Whitehouse, OH
    Don't think this is true since .9.2... the only thing VFR doesn't seem to like is PAL sources. I use it on all encodes, and have been doing so for quite awhile now with no issues.

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