What does handbrake do -> file size?

Discussion in 'Apple TV and Home Theater' started by VideoBeagle, Dec 17, 2013.

  1. VideoBeagle macrumors 6502a

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    #1
    So, I have some Blu-Ray rips that I'm running thru Handbrake with the Apple TV3 preset (for use with Apple TV)

    I did a batch last night, with HUGE variation in results

    One reduced size from14.32hb to 3.97Gigs((28%)...another from 11.31gb to 10.35gigs (92%).

    They seem to be pretty similar, though the first one is a up/down 3d video.
    Using the same file pre-set.

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    Why is there such a difference in the output file size?
     
  2. Menel macrumors 603

    Menel

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    #2
    What did you change during the different encodes?

    length of file?
    bitrate of file?
     
  3. dynaflash macrumors 68020

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    #3
    The HB presets use Constant Quality encoding. This is old news. Basically a given quality (based on the RF value) is given and HB will use whatever bitrate needed to achieve said visual quality. Typically complex and/or grainy sources will require more bitrate to achieve said quality.

    For more read here: https://trac.handbrake.fr/wiki/ConstantQuality

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    Oh, plus the larger ones are 1920 x 1080 whereas the smaller ones are 1920 x 940. Smaller source size == smaller sized encode all other things being equal.

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    Though based on a percentage from source to final encode its gonna be the complexity / graininess of the source since you would be comparing the same sized frame for the same source.
     
  4. cardsdoc macrumors 6502

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    #4
    I've found degree of film grain makes a huge difference. With same settings file size can range from 4GB to 12GB on my encodes.
     
  5. paulrbeers macrumors 68040

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    #5
    Think of two frames of video. Only what changes from one frame to another is written. Any data that stays the same is ignored. Thus, cartoons and (newer) romantic comedies usually use the least amount of data once run through Handbrake. However, older films with lots of grainy video or action flicks will require much larger files.

    Comparing two videos for file size will mean nothing. Now if you converted the same movie twice and ended up with dramatically different file sizes, then there would be a problem.
     
  6. VideoBeagle thread starter macrumors 6502a

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    #6
    well the one with the big reduction is a rip of Amazing Spider-Man (the newest one) 3d, while the other is the 1990 TMNT movie which certainly looks grainier.

    The 3d does have a large black band in the middle (that becomes the letter boxing when in 3d mode) so if data that doesn't change between frames gets ignored, that,s a lot that will be ignored (and explains why I see such a high file size reduction in 3d films vs 2d).

    I'll have to play with the quality of the TMNT encode. As the rip goes to permanent storage, 10 gigs is just a much bigger file than I really want.

    Thanks for the info's!
     
  7. priitv8 macrumors 68020

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    #7
    Anithyng on celluloid is a headache for H.264 (or any) digital encoder, because film grain is essentially a white (totally random, unpredictable) noise.
    Everything produced digitally is no problem and looks better.
     
  8. mpantone macrumors 6502

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    #8
    This is utter poppycock.

    I've used Handbrake to transcode DVDs of 50+ year old movies (*cough* Hitchcock *cough*). A lot of these digital video encoding algorithms were written before digital video took over mainstream media.
     
  9. priitv8, Dec 18, 2013
    Last edited: Dec 18, 2013

    priitv8 macrumors 68020

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    #9
    You can put it that way, if you will.
    Most digital compression works on temporal compression, just as paulrbeers explained above. Film grain does introduce unpredictability to the process.
    This doesn't mean, these movies don't encode. But you have to admit that a 100% digitally mastered piece (Avatar, any recent animation) looks brilliant, even at lower bitrates?

    PS If you sourced your material from DVD, it was digital even before you started to Handbrake them! So the original MPEG-2 encoder in the studio went already through this denoise headache.
    http://forum.doom9.org/archive/index.php/t-46906.html
     
  10. gnasher729 macrumors P6

    gnasher729

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    #10
    The only problem is when you use Handbrake with "fixed quality" setting. With that setting it will desperately try to reproduce any fault (graining etc. ) in your old movie, creating huge files. And it doesn't improve your viewing one bit because what it reproduces are faults anyway. If you use a fixed file size, those faults won't be reproduced. Probably even looks better.

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    Well, compressing some 1920's black and white movies from DVD with not-very-high fixed quality gave me just awful file sizes.
     
  11. cardsdoc macrumors 6502

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    #11
    Film grain is often a desired effect by the director, not a "fault". I just encoded Man of Steel from blu ray which has a lot of grain, hence about a 12GB file using AppleTV3 preset. Handbrake appropriately keeps the grain intact. If you tried to remove grain by altering settings you would loose detail and the intended effect.
     
  12. VideoBeagle thread starter macrumors 6502a

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    #12


    Hmm...I was looking for such a setting in HB and failing...time to get a googling.
     
  13. dynaflash macrumors 68020

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    #13
    Target file size was removed in HB 0.9.6. And no it will not look better than constant quality. That makes no sense.

    If you want to remove some grain and therefore reduce files size either raise the rf value (which lowers the target quality) or try the denoise filter in picture settings. The filter will remove some of the grain and noise on grainy sources before it hits the encoder therefore reducing the file size. I would start with a weak setting and test a clip as on strong settings you can end up with a "plastic" look to the picture.
     

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