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Thread: PowerColor SCS3 Radeon HD 4650 512MB

  1. #1
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    Default PowerColor SCS3 Radeon HD 4650 512MB

    Phoronix: PowerColor SCS3 Radeon HD 4650 512MB

    Back in December we looked at the Sapphire Radeon HD 4650 512MB OC graphics card. This mid-range ATI graphics card had performed well under Linux and what separated it from the other Radeon HD 4650 graphics cards on the market was its factory overclock of 650/900MHz. While not factory overclocked beyond the RV730PRO specifications, PowerColor has the PowerColor SCS3 Radeon HD 4650 512MB, which instead offers passive cooling. Is this an ideal candidate for a Linux-based HTPC? In this article we are looking at the PowerColor SCS3 Radeon HD 4650 512MB.

    http://www.phoronix.com/vr.php?view=13631

  2. #2
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    The Catalyst driver does support XvMC
    It does? blabla ten character limit

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    Quote Originally Posted by Zhick View Post
    It does? blabla ten character limit
    What the hell, 10 character limit?

    I would have thought all graphics cards be able to do hd (h264) playback acceleration by now. Even older cards like x1600 series..?

    Not sure I'm a fan of fanless GPU's either because usually they get very hot. So hot I could probably fry an egg on one.

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    Just to be clear, the issue here is how *much* of the playback work is being accelerated, not whether there is acceleration at all.

    The open drivers currently accelerate scaling and colour space conversion, but not bitstream decode, IQ, IDCT or MC.
    Last edited by bridgman; 03-26-2009 at 11:04 AM.

  5. #5
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    Well, BitStream is one of most awaiting features for me ;-) On windows it works well, actually it's kinda funny to watch 1080p movie + 3 or 4 shaders combined with 0%CPU/0-2%GPU on HD4850, when CPU does the same with 30-40% of usage ;-)

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    Bridgman, correct me if I'm wrong, but you get a better image quality using a GPU acceleration instead of a CPU acceleration. I have in mind that the more you use the GPU, the best picture you get (ride of artefact mpeg for example, better scaling, etc.)

    Because the GPU can achieve far more of this specific calculation than a CPU could ever do.

    Finally, the question is not so much acceleration (a quad core can do the job even for 1080i I guess) but rather for quality.
    Isn't it ?

    I'll also be very happy when it would be possible to encode videos using the GPU, as it's already possible to do with fglrx in Windows. I don't have windows, but even if my C2Q can handle my m2ts files conversions, I'll be more than happy to use my 4870 to convert my videos...

  7. #7
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    Whats the point behind this card? Specs are a bit weird. Is it meant for only HTPC? GPU seems pretty powerful. But 128-bit is a little low perhaps? And DDR2?? Surely surely not for gaming .

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    Quote Originally Posted by Fixxer_Linux View Post
    Bridgman, correct me if I'm wrong, but you get a better image quality using a GPU acceleration instead of a CPU acceleration. I have in mind that the more you use the GPU, the best picture you get (ride of artefact mpeg for example, better scaling, etc.)

    Because the GPU can achieve far more of this specific calculation than a CPU could ever do.
    Most of the opportunities to improve image quality (filtering, fancy di-interlacing, post-filtering etc..) are in the render part of the pipe, which is already accelerated.

    For the decode part of the pipe (the first part) you basically "follow the instructions" with very few opportunities to improve quality.

    Most of the image enhancement stuff is shader-based, working on the fully decoded image, so it pretty much has to be in the "render" part of the pipe. You can think of the Xv API as the dividing line between "decode" and "render".

    The order of the last few steps can change, and steps can be combined in a single shader :

    bitstream <<- VDPAU, VA-API, XvBA start here (or lower)
    IQ
    IDCT <<- XvMC starts here
    MC <<- or here
    deblock
    colour space conversion <<- Xv starts here
    post-filtering
    de-interlacing
    scaling

    ---------


    Quote Originally Posted by Fixxer_Linux View Post
    Finally, the question is not so much acceleration (a quad core can do the job even for 1080i I guess) but rather for quality. Isn't it ?
    Decode acceleration is mostly about reducing CPU utilization and power consumption. Render acceleration does as much or more to reduce CPU utilization, but there are also opportunities to improve image quality. Scaling and MC usually put the biggest load on the CPU.

    All of the steps from MC down are great candidates for processing with shaders. Most of the earlier steps (from IQ on down) can also be done on shaders but dainty, dedicated hardware can usually do the same work with less power consumption.
    Last edited by bridgman; 03-26-2009 at 01:40 PM.

  9. #9
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    Quote Originally Posted by bridgman View Post
    The order of the last few steps can change, and steps can be combined in a single shader :

    bitstream <<- VDPAU, VA-API, XvBA start here (or lower)
    IQ
    IDCT <<- XvMC starts here
    MC <<- or here
    deblock
    colour space conversion <<- Xv starts here
    post-filtering
    de-interlacing
    scaling
    So does that mean around 25% of that stack is currently being accelerated by the GPU?

  10. #10
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    In terms of steps, I guess it's 4 out of 9 or 44%. In terms of CPU it's probably about the same or maybe a bit lower -- MC and scaling are the biggest CPU hogs.

    The relative CPU utilization in the different stages changes a fair amount depending on the encoder and the encoding parameters that were used.

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