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  1. Member
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    Hi

    What are GOP-accurate editors? Can you name some of them? What are different between GOP-accurate editors and MPEG editors? Which one is better for editing MPEG files and why?
    Thanks
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  2. A GOP is a Group Of Picutures, a sequence starting with a keyframe (like a jpeg encoded picture) and several frames which only encode the differences between frames (called predicted frames). When there's little motion in the video the predicted frames can be very small, saving a lot on the file size. MPEG files typically have GOPs of about 15 frames. Divx files may have GOPs of 300 frames or larger.

    A GOP accurate editor is an editor which only cuts on keyframes. This type of editor doesn't reencode any of the video so it is very fast and the video is not degrade at all. But you can only make cuts in certain locations.

    Some editors will allow you to cut on any frame but will reencode the entire video if you make any changes. This will be very slow and will reduce the picture quality to some extent.

    Then there are smart editors that will only encode the frames within the GOPs that are cut. These are fast and only degrade the picture during the reencoded GOPs.

    Which type of editor you want depends on what you want to do and what type of video you are editing.
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  3. Member
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    Thanks for your answer, as you said mpeg editors divide into 3 categories, can you introduce some soft wares for each categories?
    You said GOP accurate editors do not degrade streams But I can only make cuts in certain locations, how can we find these certain locations?
    Do we have limitation if we want to cut and remove some part of MPEG files by GOP accurate editor?
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  4. Originally Posted by Sean_ve99
    You said GOP accurate editors do not degrade streams But I can only make cuts in certain locations, how can we find these certain locations?
    Do we have limitation if we want to cut and remove some part of MPEG files by GOP accurate editor?
    GOP accurate editors will usually just show the keyframes where you are allowed to cut. With MPEG video this is typically about every half second.

    I don't do a lot of MPEG editing so I'll leave it up to others to suggest which programs to use.
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    You mean cut points will be determined by GOP accurate editor? And I can't cut any frames?
    It means that if I have 2 second mpeg video, I just can cut video on frame 15 and 30 and 45?
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  6. Originally Posted by Sean_ve99
    You mean cut points will be determined by GOP accurate editor? And I can't cut any frames?
    It means that if I have 2 second mpeg video, I just can cut video on frame 15 and 30 and 45?
    Yes, assuming that video has a new GOP every 15 frames. The GOP size can vary. For example, many MPEG encoders will start a new GOP when there is a sudden scene change.
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  7. Member
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    I want to cut and remove some part of mpeg video, I want to do it by GOP accurate editor and smart editor (I want to check it by both applications) do you have any suggestion?
    Anybody can tell me which applications I could use?
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  8. Womble's MPEG editors are frame accurate and smart.

    http://www.womble.com/

    I believe Sony's Vegas is a smart MPEG2 editor.

    There are some free GOP accurate MPEG editors. But I think they require elementary streams (video only, no audio). MPG2CUT2, MPEG2Schnitt, Cuttermaran, etc.

    Search the tools section for MPEG editors:

    https://www.videohelp.com/tools?toolsearch=&s=107&orderby=Name&hits=50&convert=&dvdauth...+or+List+tools
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  9. Member
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    Thanks,
    I hope to get more information about GOP accurate editors, type of them and their advantages and disadvantages in compare with smart editors?
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  10. Member The_Doman's Avatar
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    TMPGenc MPEG Editor is also a very good smart/frame accurate editor.

    TMPGEnc MPEG Editor 2.0
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  11. Member
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    It is sometimes difficult to tell if you have an open GOP after editing and cutting. There is a nice feature in the authoring program, DVD Lab that gives a warning when you import Mpegs that have open GOPs.
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  12. And VideoReDo will also cut on any frame and only encode what needs to be done not the whole video. Using the definition given above you would call this a smart editor.

    I like it because of the interface is so easy to use. Keyboard or mouse wheel for forward and reverse as well as different speeds and so on.

    I just used it tonight in fact to fix a damaged mpg file that my DVD authoring app rejected, TDA . I used the Quickstreamfix tool.

    To use the product blurb from here
    https://www.videohelp.com/tools/VideoReDo
    "VideoReDo is the perfect tool to edit your MPEG1/MPEG2 files. Whether you create digital video by capturing off-the-air programs, convert analog (VHS) tapes, HDTV, DigitalTV, DVB, TivO, ReplayTV, DVR-MS or extract chapters from DVDs, VideoReDo makes fast work of trimming, cutting, and/or joining your MPEG compressed digital images. Repair/fix MPEG streams. "

    I and others on another forum have found them to be very responsive for feature requests and to make it work with non standard mpg files. I use it myself via QuickStreamFix to fix errors in a DVB file and output as a ready to use mpg file when done. Having it work with this particular dvb file took tweaking by them. Drop by their forum and go through the message base.

    The other thing I liked was they gave tech support when I was still using the trial. Don't forget to get the free trial key or it will only output 30minutes of video. With the free trial key it becomes unrestricted.
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