[Ffmpeg-devel] av_seek_frame() units

Dave Dodge dododge
Fri Jul 8 04:14:42 CEST 2005

On Wed, Jul 06, 2005 at 03:59:29PM -0700, Steve Willis wrote:
> Does anyone have any insight on how "professional" video editing
> programs like Adobe Premiere allow users to treat any frame as a
> keyframe?

My guess would be that when you "import" a video clip as part of a
project it either converts it immediately to its own internal format
or builds some sort of index so that it can get to the frames.  A
quick googling indicates that Premiere needs you to provide a large
"scratch" area for it to use to hold these files, but I can't find
anything that describes the actual file formats that are used there.

Premiere's knowlege base has this interesting note about importing
and editing MPEG files, which suggests that even the "pro" tools might
have some issues with predictive formats:

    Although Premiere can import and export MPEG files, Adobe
    recommends that you don't use MPEG files as source files in a
    Premiere project. Instead, use MPEG as the final output format of
    your project. MPEG files don't lend themselves to editing because
    the video frames in an MPEG file aren't self-contained. That is,
    any given video frame contains only the information that has
    changed from the previous frame. During editing, a previous frame
    required to fully decompress a given frame may not be present,
    resulting in poor quality of the final rendered frame.

                                                  -Dave Dodge

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