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  1. Member
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    What if I were to render a nice uncompressed avi file, then convert it to a very good quaility divx or xvid file. From here I would then encode to mpeg 2 and go to SVCD with it.

    Question: would I get a smaller file, and technically more time on the SVCD, than if I were just to encode the original avi? Does the divx encoding stay embedded while it goes over to mpeg2?

    Tygrus
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  2. Member Conquest10's Avatar
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    i don't think you understand the process of converting.
    His name was MackemX

    What kind of a man are you? The guy is unconscious in a coma and you don't have the guts to kiss his girlfriend?
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  3. Member
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    Mpeg is a compression algorithm, just like DIVX is....no magic there. Since you technically cant apply mpeg compression to the same files twice, cause you will get the same thing again, the idea was to apply a different compression up front in the original file.
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  4. Member Conquest10's Avatar
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    well, you will get a smaller file if you encode at a lower bitrate.
    His name was MackemX

    What kind of a man are you? The guy is unconscious in a coma and you don't have the guts to kiss his girlfriend?
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  5. Member Cornucopia's Avatar
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    You CAN apply compression to the same file twice. When opening up the file in most apps, the file is decoded and uncompressed for viewing/playing, so it will happily try to compress again. This won't change the file as much as there is less entropy than during the 1st compression, but it will still happen every time--and NOT for the better.

    I have specifically done multi-generational tests on AVID MJPEG, DV, MPG1 and MPG2 files, just to examine the change and know what the extent of reliability you will have.

    BTW, you will almost always get a better encode by using an uncompressed file as opposed to a compressed one. The compressor can do a better job of estimation and averaging when given a full-range, high-rez original source. The only benefit would be if the compressed version had included some Noise-reducing/Smoothing preprocessing. In that case, the benefit really comes from the reducing of the entropy (Noise/Randomness).

    My recommendation:
    Go back to the source.
    Encode small samples in various ways until you get the quality you can accept given the bitrate that you require.
    Save that setting and then do a full encode of the whole thing using that setting.
    I'd try samples that included Fast Motion, Slow Motion, No Motion, Fast Editing, Smooth Transition--Dissolve or Wipe, along with High Detail vs. Smooth Gradient Backgrounds. Blue colors and moving small angular text and slow lateral camera pans can be particularly challenging.
    If you satisfy all these requirements, you should feel comfortable with the remainder of the program being OK.

    Remember the saying "Garbage In--Garbage Out". Well the popular codecs are Lossy and applying such loss tends the file towards Garbage-ness.

    HTH,
    Scott
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