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MPEG-4

Discussion in 'Other video questions' started by wscici, Jul 30, 2002.

  1. wscici

    wscici Member

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    Hi,

    I'm new at this and was wondering if anyone knows whether there are or will be actual files out there with an .mp4 extension. In other words, can mpeg-4 be an actual file format, like mpeg1 and mpeg2, or is it only used as a CODEC?

    Thanks.
     
  2. ALLLVOLLL

    ALLLVOLLL Member

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    MPEG-4 HAS A FILE EXTENSION OF .AVI ALTHOUGH IT IS DIFFERENT FROM TRADITIONAL .AVI FILES.IT STILL IS ACTUALLY MPEG FORMAT.
     
  3. dRD

    dRD I hate titles Staff Member

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    MPEG-4, just like virtually any other video format, can be stored in _any_ container format, so claiming that MPEG-4's extension is AVI is b.s.

    AVI/ASF/QuickTime/MP4 doesn't tell _anything_ about the fact which compression method was used.

    So, your question is flawed -- there isn't anything called "real video formats". Just compression routines and container formats ("holders", "wrappers" or whatever you want to call them). MPEG-1 and MPEG-2 require codecs, just like MPEG-4 does. Only difference is that MPEG-1 codec comes bundled with Windows and MPEG-2 codec with DVD player software (for obvious reasons as DVD-Videos are MPEG-2s).

    To put it simply:

    MPEG-1 can have extensions of .avi, .mpg, .qt, .mp4, .ogm, etc...
    MPEG-4 can have extensions of .avi, .qt, .mp4, .ogm, etc...

    ...there is NO such compression format as "AVI".
     
  4. ALLLVOLLL

    ALLLVOLLL Member

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    I THINK YOU OBVIOUSLY NEED TO READ MY REPLY A LITTLE SLOWER,BEFORE ACTING LIKE A KNOW-IT-ALL,& TELLING ME I'M FULL OF IT.I NEVER CLAIMED .AVI WAS A COMPRESSION FORMAT.I WAS MAKING THE POINT THAT WHEN YOU PRODUCE AN MPEG-4 VIDEO IT WILL USUALLY HAVE AN .AVI EXTENSION.(THAT IS 99% OF THE VIDEO PRODUCTION/CONVERSION UTILITIES AVAILABLE TO THE PUBLIC WILL PRODUCE AN MPEG-4 WITH AN .AVI EXTENSION.)I'VE NEVER SEEN A "DivX" COMPRESSED VIDEO WITH AN EXTENSION OTHER THAN .AVI.IF THERE IS,IT ISN'T COMMON OR POPULAR ENOUGH FOR MOST PEOPLE TO CARE ABOUT.(UNLESS IT WAS .MPG)
     
  5. dRD

    dRD I hate titles Staff Member

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    Umh, you didn't say anything that there are other options as well, giving the false impression that MPEG-4 has .avi extension always. To be more specific, helluva lots of MPEG-4 files nowadays are in QuickTime format, with an extension of .qt as well as in MPEG-4's _OWN_ native wrapper, .mp4.

    And don't yell, it's really annoying to read.
     
  6. wscici

    wscici Member

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    So the wrapper (for example, the mp4 wrapper) is just something which contains the compressed file data?

    How does the whole process work? For example, I know that the MPEG standard provides a lot of tools for the user to use. What does this exactly mean? Do the developers take these tools and write their own encoder / decoder? And then the files that get encoded / decoded can have basically any extension?
     
  7. dRD

    dRD I hate titles Staff Member

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    In MPEG-1 and MPEG-2 there's a kinda consensus that everybody uses MPEG-1/2 specific wrappers, even that you can use other ones as well -- actually latest TMPGEnc can encode MPEG-1/2 videos and wrap the files within AVI wrapper.

    And yes, that is the process pretty much, developers do develop their encoding routines and decide what different wrappers they will use -- some encoders, like TMPGEnc, offer multiple wrapper possibilities like I said in above test. But basically in normal everyday life there's a consensus among wrappers and most common video formats -- MPEG-1/2 use their own and most MPEG-4 encoders (like DivX) tend to use AVI as a wrapper (most notably because there's a huge selection of AVI-supporting video editors available while MP4 -- or other varieties -- doesn't have very many supporting apps yet).
     
  8. wscici

    wscici Member

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    Could you tell me what the difference is between a proprietary format like QuickTime and a standard, such as MPEG-4?

    Thanks a lot for your help!
     
  9. dRD

    dRD I hate titles Staff Member

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    QuickTime is just a wrapper, just like AVI -- but in 99% of the cases people refer to it as Apple's encoding standard as well.

    The latest QT format Apple has, uses standard MPEG-4 encoding and therefor there isn't anything different with it compared to any other MPEG-4 (like DivX5 which is MPEG-4 as well) other than the fact that its wrapper is QT. If you encode "QT video" and use AVI or MP4 wrapper, it is identical -- in terms of compatibility, etc -- to those made with DivX5 (or XviD, etc).
     
  10. wscici

    wscici Member

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    How does one decide which wrapper to use? If I want to encode using MPEG-4 compression, then how do I choose between avi or qt or wmv or what not?
     
  11. dRD

    dRD I hate titles Staff Member

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    Depends really what software you use -- like I said, most of the tools only support AVI as a wrapper, although DivX5 has a tool that allows you to convert AVI-wrapped MPEG-4 files to use MP4 wrapper as well.
     
  12. wscici

    wscici Member

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    Thanks for all your help so far!
     
  13. wscici

    wscici Member

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    One more question. I have been looking at the information provided by MPEG LA regarding licensing, and am confused about the licensing procedure for MPEG-4.

    If one were to develop their own MPEG-4 codec and use it within a software product to let end users create their own MPEG-4 encoded files, what licensing fees need to be paid? Would that fit under the licensing agreements for MPEG-4 Visual Patent Portfolio License? Except there is no specific section under that License which seems to include this type of issue, to me at least.

    Thanks if anyone is able to answer this question.
     
  14. acoustic

    acoustic Member

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    Does Divx Pro 5.2 use a "better" or different mpeg4 coding than other software or is there only one standard such that all mpeg4's are the same?

    Along those same lines, the Divx website was a little confusing and seemed to imply that their pro version would use more advanced coding/decoding techniques than their "free" version. Again, would the free version have to produce equal results as the for-pay version because all mpeg4's are the same?

    Thanks for your help!

     
    Last edited: Sep 5, 2002
  15. dRD

    dRD I hate titles Staff Member

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    No, it doesn't. And there are several "layers" or "levels" of MPEG-4, but virtually all MPEG-4 encoders produce the same basic layers as DivX does. But of course there are differences in videos they produce, just like MPEG-1 encoders -- format is _exactly_ the same, but how they achieve their results, varys: TMPGEnc produces excellent MPEG-1 video and meanwhile some other tools, like LSX produce pretty horrible results. And both are 100% MPEG-1 compliant, same filesize and everything.
     
  16. Houkan

    Houkan Member

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    So, in theory, I could extract the video data from an .mp4 file created by QuickTime and stuff it into a .ogm file to have it be played back by the Divx, or Xvid codecs (in windows media player), provided I had the proper software?
    (I hate the quicktime player: no real fullscreen support)

    I am sure there is more to it than that, especially since Divx encodes can't always be decoded by Xvid, and vice versa.

    Also, is there a corresponding MPEG4 audio codec?
     
  17. dRD

    dRD I hate titles Staff Member

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    Basically yes, you're right. Or actually you wouldn't even need to transfer the data from .mp4 container to .ogm container and DivX, XviD or ffdshow should be able to decode it anyway.

    Currently MPEG-4 is in kinda chaotic state, but within next year there should be tools available and glitches between encoders have been solved.
     
  18. streetcav

    streetcav Guest

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