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Thread: PBO improves performance???

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  1. #1
    Junior Member Newbie
    Join Date
    Sep 2012
    Posts
    2

    PBO improves performance???

    Hi,

    I have modified the PBO unpack code supplied in here, to have multiple textures all connected to its individual PBO. However when I test the code with and without PBO it turns out that without PBO gives better performance.

    My modifications on the code are pretty straight forwards. I only changed these three variables to arrays

    Code :
    GLuint pboIds[numFrames];                   // IDs of PBO
    GLuint textureId[numFrames];                   // ID of texture
    GLubyte* imageData[numFrames];             // pointer to texture buffer

    and read each PBO to corresponding texture and update PBO s in a for loop. However when you switch off the usage of PBO by pressing 'space' you see the copy time is reduced.

    So I wonder why the performance is poor with PBOs. In my project I need to display multiple videos on the screen should I not use PBOs?

    My XCode project is in
    https://docs.google.com/open?id=0BwYp7k9vQEPrQWJRSVZLSXpaaE0

    AmI missing some thing.

    thanks
    mike

  2. #2
    Intern Contributor
    Join Date
    May 2008
    Location
    USA
    Posts
    99
    Generally what people miss with PBOs is that they free up the CPU to do extra work. If you don't do any extra work, then you won't get the benefit - you're just using a different transfer mechanism.

    There's also some pixel format requirements to look at. If you don't have a pixel format that can be transferred without CPU help, you won't get asynchronous transfers either.

    Bruce

  3. #3

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