Is GPU Transcoding still inferior quality wise?

Discussion in 'Videocards vs General Purpose - NVIDIA Ageia PhysX' started by helphelphelp, Nov 30, 2012.

  1. helphelphelp

    helphelphelp Member

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    HI Guru's

    i know this is probly a simple one for many of you. I have read alot of articles from 2011 and Q2 2012 saying that GPU transcoding (fully) or assisted with quicksync has lower quality outputs than pure CPU encoding with handbrake.
    is this still the case or have nvidia/ati drivers picked up the slack?

    The outcome of this will determine whether or not i purchase a top cpu, or a mid-top cpu and mid-top gpu.


    :)
     
  2. thatguy91

    thatguy91 Ancient Guru

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    Video encoding is still better on the CPU. The problem with video encoding is the amount of data and the functions that would actually benefit from running on a GPU. After considerable tests it has been found that it is really only motion estimation that benefits from running on the GPU, and this means bandwidth consumption required to transfer data back and forth between the GPU and the CPU. Integrated GPU's therefore benefit more from this than discrete GPU's. The most likely tool you will use to encode is x264. There is a test patch for that to use the GPU for the things that benefit from it (and the things that won't impact other things) but it only gives a couple of frames benefit. In the future when heterogeneous CPU/GPU architectures are available there will be benefit from this, but at the moment you would be best to stick with getting a good CPU for encoding.

    Remember though that the encode speed can only be good as the slowest part of the pipeline, but if you be sensible an i7 would be beneficial if you plan to do considerable amounts of encoding.

    Just remember that GUI frontends need tweaking. Running x264 for example using default settings leads to a great quality output, but it could better by using more strict settings (drops the framerate). The benefit from actually using better and slower encode settings is not only the output will be better, but you are reducing the affects of any performance choking filters that may be used.
     
  3. helphelphelp

    helphelphelp Member

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    Thanks for the reply! CPU is the way to go ! also its cheaper overall and thats not even including power consumption
     
  4. Spets

    Spets Ancient Guru

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    GPU encoding has come a long way, you just need to make sure you don't use outdated software.
    Image on the left was done on CPU (2600k @ 4.5ghz) took 1:36 to do a 3min scene.
    Image on the right done on GPU via CUDA (GTX 460) 0:58 same 3min scene.

    [​IMG]
    Full image:
    http://postimage.org/image/suh8baskt/full/
     

  5. ShutDown_Hussain

    ShutDown_Hussain Active Member

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    which video converter did you use?
     
  6. LNCPapa

    LNCPapa Master Guru

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    These are two different frames - any chance of posting the same frame for the comparison?
     
  7. Spets

    Spets Ancient Guru

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    For this I was just running Freemake Video Converter, pretty good for an average user.

    I forgot to add though, if you're transcoding something for a client then I strongly recommend only using the CPU. For home videos, basic or fast conversions I dare say GPU quality has improved enough for use.

    Sorry, was in a rush that day.

    [​IMG]
    Larger image: http://postimage.org/image/f0zodvshn/full/
     
    Last edited: Jan 23, 2013
  8. ShutDown_Hussain

    ShutDown_Hussain Active Member

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    i used freemake today and i must say video quality is not bad but not enough tweaking. also only dxva for amd graphics cards. can you name a free amd app supporting video converter.
    also was there any difference of filesize between your cpu vs gpu transcoded files.
    thank you.
     
  9. Spets

    Spets Ancient Guru

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    There was only a 1.8% difference in size, CPU being smaller.
    Some free ones available are Any Video Converter, DVDVideoSoft and MediaCoder. I'm not too sure if they use APP but from what I've heard DXVA is your best bet.
    Some cheap converters out are DvDFab, Xilisoft, TMPGEnc and 4Videosoft Video Converter. I recommend DvDFab, I've had a good experience with them.
    IIRC DvDFab, Xilisoft and 4Videosoft also use APP.
     
  10. ShutDown_Hussain

    ShutDown_Hussain Active Member

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    thank you.
     

  11. thatguy91

    thatguy91 Ancient Guru

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    It does appear the CPU encoding is a little clearer (which it should be), but then of course, there's the question of what actual encoder you used (most encoders are just frontends), and if it is a frontend what library and version was used for the conversion? and of course, all the settings used. For x264 for example, the current build is r2245. Builds often contain performance or quality improvements. More standard settings frontends may use are subme 5, Hex ME, 3 ref frames, 3 b-frames (using the old search method), etc. Better settings would be Subme 10, UMH ME, 5 ref frames, 5 b-frames (using optimal b-frame search method), and maybe auto-variance AQ, with a ME search range of 24, and a small amount of psy-trellis (0.1 for example).
     
  12. ShutDown_Hussain

    ShutDown_Hussain Active Member

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    has anyone got hands on the open cl version of handbrake.
     

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