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Thread: hierarchical coding ratio

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    hierarchical coding ratio

    I know this is a rough subject given the amount of variables. With that in mind, if you were using h.264 to compress say a wmv file. Do you have any idea of the size ratio of an original compressed package to a package that has been taken to the lowest possible hierarchical level before any noticeable loss in picture quality? I know that lossy can be taken to a size of around 100:1 before a loss in picture quality and was wondering if the same ratio or at least near the same ratio applied to a lower level. I would just make it lossy to save myself a lot of time but it would be compressed before I ever got a hold of it. So, in order to minimize latency I wanted to just manipulate the package without decompression. Thanks

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    Anyone?

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    Either my English is poor or your English is poor. I cannot understand your post.

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    I agree with Piotr. It's hard to make out what you're after. Still, I'll give it a try:

    Quote Originally Posted by WillatSMU View Post
    Do you have any idea of the size ratio of an original compressed package to a package that has been taken to the lowest possible hierarchical level before any noticeable loss in picture quality?
    That depends on the codec, source material and its quality and will therefore vary from video to video. If you want to know the ratio to actually determine how much space you'll save in the long run for a big project, then only a test encode would give you a clear answer.


    Quote Originally Posted by WillatSMU View Post
    I know that lossy can be taken to a size of around 100:1 before a loss in picture quality and was wondering if the same ratio or at least near the same ratio applied to a lower level.
    Lower level of what? Btw, you can't generalize ratio like that. That doesn't work out at all. For example, encoding a flash video consisting only of vector graphics with clean textures and little color variation (or an opera recording) will compress at a much higher ratio without visible loss in quality than content with complex color schemes, tons of detail and fast scene switches such as fast paced sports events or action movies. Ratio also depends heavily on the use of B and P-frames, the question of how many of those you allow between I-frames as well as how much you're willing to sacrifice hardware support and lower playback requirements for more efficient and CPU-intense encoding algorithms which vary from encoder to encoder.


    Quote Originally Posted by WillatSMU View Post
    So, in order to minimize latency I wanted to just manipulate the package without decompression.
    This is where I'm lost. What kind of latency are you talking about? Are talking about network streaming or the decoding latency from chip to the screen? Also, what do you want to manipulate about it? There are tons of flags you can change without re-encoding the whole thing, but also many things that can't be done without it.


    Edit: Just to give you an idea of what ratio you can expect for lossy but without visible loss of quality, I dug up one of my test videos which consists of 1963 frames of a terragen animated 3D-rendered landscape with a resolution of 720x576 @25fps. I used Megui with my personal ultra-quality profile which uses all image enhancing encoding strategies available by the encoder together with a constant quality quantizer. I went through two encodes with two quantizers. Both are the lower and upper values specified by Megui for excellent encodes, Q18 being the one described by Megui as producing visually lossless encodes.

    Uncompressed size: 2.442.392.082 Bytes
    Megui Q18: 67.174.186 Bytes --> Ratio 1:36
    Megui Q21.5: 42.680.663 Bytes --> Ratio 1:57

    As you can see, the ratios are far from 1:100. Also, both of them vary greatly. That doesn't mean that a ratio of 1:100 isn't possible, it just proves that generalizing doesn't work, even if you have the same source material at hand, especially when dealing with something subjective as visually lossless quality.
    Last edited by Mexxi; 11th May 2012 at 16:03.

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    Sorry about that it was written really quickly. To answers your questions in order

    x264

    Lower quality of video using hierarchical coding vs using lossy to drop pixel density and I know but unfortunately it is impossible to test all the variables but a best case, worst case scenario is the best I can anticipate. Also, complex color schemes, high details and very few changes from scene to scene.

    wmv compressed in h.264 it is 720 @24fps

    Latency of transferring the video over the network

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