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Thread: Transcoder Add-on quality and CBR vs. VBR

  1. #1
    Join Date
    Oct 2008
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    22

    Default Transcoder Add-on quality and CBR vs. VBR

    Hi,

    I've been trialling Transcoder, with some success.
    1. Why is video quality lower when CUDA accererated transcoding (acctulaty transrating) is used?
    1a. Is the quality lower also when quicksync acceleration is used?
    2. Output bitrarte seem very VBR, is there a way to make bitrate more constant so it does not exceed some limit?
    3. Is there a way to "reboot" Transcoder process so it can reread new settgins in xml?


    Tnx in advance.

    A.

  2. #2
    Join Date
    Sep 2011
    Posts
    1,921

    Default

    Hi
    The output quality is very much dependent on the input quality.
    For example,
    1.) 256k audio stream being transcoded or transrated to 64k
    2.) 128k audio stream being transcoded or transrated to 64k

    Example 1 will sound much better than example 2.
    Although the output bitrate is the same the stream quality was better to start with.

    Of course the source will sound the best in either scenario because lowing the bitrate makes you loose quality.

    I haven't noticed any change in quality difference using CUDA and/or Quicksync when transcoding.
    Restarting a stream will make the transcoder read the files again so this will allow the new settings to take effect.

    Jason
    Last edited by JasonH; 07-19-2012 at 04:04 AM.

  3. #3
    Join Date
    Oct 2008
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    22

    Default

    Jason what i had in mind was video transcoding, there is noticable difference if CUDA is used instead of default (CPU), transcoding engine.

    a

  4. #4
    Join Date
    Sep 2011
    Posts
    1,921

    Default

    Hi
    I was saying that if you compare CUDA vs QuickSync they are of equal quality, they are both better than using CPU to transcode.

    The logs will tell you of the default chosen,
    I have both CUDA and QuickSync on this pc but if the CPU is found first then CPU will be the default but that's not always the case, it may be CUDA or QuickSync that's the default.

    Jason

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