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PowerColor SCS3 Radeon HD 4650 512MB

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  • #16
    Yeah, Xv is pretty widely supported so most decoders will use it for output -- and that gets you acceleration for the final steps in the playback stack.

    The upper parts of the stack handle "decoding" - going from a compressed bitstream to an uncompressed YCbCr image in whatever resolution the video was recorded, and the lower parts of the stack handle "rendering" -- getting that YCbCR image on the screen in RGB and the size you want to view it.

    The bitstream format is different for every video format, but they all decompress to YCbCR and that's what gets passed to Xv (so yeah, Xv works for H.264, MPEG4 part 2, VC-1 etc..). The Xv acceleration handles conversion from YCrCb to RGB and scaling from "video" resolution to "window" resolution, plus some filtering.

    I think some decoders perform de-interlacing further up the stack but others let Xv do it, still learning that part.
    Last edited by bridgman; 03-27-2009, 12:47 PM.


    • #17
      Thanks a lot for all you sharp and fast answers Bridgman.