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  1. Member
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    Hi all,

    Is anyone aware of an ffmpeg command analogous to mkvmerge's --split parts-frames command?

    As implied, I'm trying to segment some mkv's at designated IDR frames (yes, they are IDR frames) but I find that mkvmerge keeps producing some corrupt files (I am getting playback issues at random parts that don't exist in the source--I describe the issue in detail here), so I wanted to try another option. That said, I've never understood how ffmpeg does file splitting. Since I have the exact IDR frames I want to cut on, I prefer an option that allows that specificity, rather than a time-based option, which is all I can seem to find with ffmpeg.
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  2. There is no frame based option to specify the start. (you can specify the number of frame to encode, but not where to start)
    If you have a problem with mkvmerge's --split parts-frames command did you contact the mvktoolnix author? (usually a good idea)
    users currently on my ignore list: deadrats, Stears555
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  3. Member
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    Hmm, that is a bummer!

    I haven't reached out to the author directly. I did make a post in the subreddit thread that he recommends and is a moderator on. I haven't filed it as a bug report because I'm not convinced the problem is with the program vs. something about my setup. Though I can't imagine what is wrong with my setup, I also can't imagine that this would be a bug that escaped notice for everyone but me.
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  4. Member
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    Just in case others stumble upon this thread in the future with a similar problem, the solution is here.

    The short version is I still use mkvmerge to split on frames. The problem was Windows 7 does not play well with USB drives, so writing under these circumstances can produce corrupted files. I found that using smaller segments (around 30,000 frames) worked fine for me, or writing directly to an internal drive.

    ffmpeg -v error -i input -f null - 2>logfile.log command allowed me to double-check the accuracy of produced files since mkvmerge was not producing any error messages. Resulting log file should be empty for a clean copy.

    Hope that helps,
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  5. I am PLEABS
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    this is how i usually split
    Code:
    ffmpeg -i <input> -c:v copy -vf trim=start_frame=100:end_frame=151 <output>
    assume if i want to split from frame 100 to frame 150, frame 151 will be dropped
    c:v copy only can be done on keyframe.
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  6. Originally Posted by Ant_G View Post
    this is how i usually split
    Code:
    ffmpeg -i <input> -c:v copy -vf trim=start_frame=100:end_frame=151 <output>
    assume if i want to split from frame 100 to frame 150, frame 151 will be dropped
    c:v copy only can be done on keyframe.
    -vf trim (-vf anything) implies re-encode. You can't use with "stream copy" with filtering
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  7. I am PLEABS
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    my bad, i kinda forgot how to actually split it since it has been ages ago.
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  8. Member
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    Originally Posted by Ant_G View Post
    my bad, i kinda forgot how to actually split it since it has been ages ago.
    Appreciate the assistance anyway!

    I'm sure there are other programs out there can cut on keyframes without reencoding, but I couldn't find anything that surpassed mkvmerge, especially once I figured out what the problem was. So I stopped looking
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