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  1. Member Budman1's Avatar
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    This may not be the correct forum but I do use this information to cut and merge so...

    I have a video I am editing and it has several scene changes that report from FFPROBE the frame is not listed as a key frame but the frame type is 'I'. There are other scene changes that report as a key frame with a type of 'I'
    The sequence of one problem? are is, in sequences - Frame #, Frame type, Key_Frame, coded/display picture number:

    40 P 0 40
    41 P 0 41
    42 P 0 42
    43 P 0 43
    44 P 0 44
    45 I 0 45
    46 P 0 46
    47 P 0 47

    The video does not contain the Format settings (Cabac, Ref, etc.) so I can assume it has been cut mid-stream from another video. Does this mean it is an Open GOP?
    Can it be safely cut at frame 45?

    The coded/decoded number are in sequence so nothing after frame 45 needs to be decoded or displayed before frame 45. I need This information to adjust my program when determining scene changes and authenticating them that are or are not actually a scene change.
    I appreciate any help .
    Thank You
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  2. I assume you are dealing with MPEG-4 AVC or HEVC and the question is whether it's an IDR or I frame.
    iirc ffrobe would report:
    Code:
    pict_type=I
    key_frame=1
    for IDR- and
    Code:
    pict_type=I
    key_frame=0
    for I-frames.
    So that frame would be a normal I-frame and in an H.264 or H.265 stream you can run into problems if you cut there. You might be lucky if non of the following frame actually references to the I-frame, but according to the specification you might get undecodable content if you cut there.

    Can it be safely cut at frame 45?
    Safely: no

    Cu Selur
    users currently on my ignore list: deadrats, Stears555
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  3. Member Budman1's Avatar
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    Selur... perfect explanation. ProWo... great article. You both have helped me tune my cut/merge program. I guess i had unknowingly had it programmed correctly by recognising only correct,complete I frames as valid cut points.

    Thank you both for the great help!
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