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the situation is i get 8 frames with the default threshold for scenecut detection.as the key frames i get is not representive enough .so i want to turn down the threhold to get more key-frames.but i use the -g and -sc_threshold arguments in my command(reference:How to control key-frame generation of ffmpeg?) ,it donot work well.i still get the same 8 frames without any change.any ideas?

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xinwei he
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  • PICT_TYPE_I should output only key frames (I frames). if you run ffprobe -show_frames on your video does it list any frames that you did not get thumbnails for? – user3770489 Feb 24 '16 at 10:19
  • my last comment should say 'does it list any I frames that you did not get thumbnails for?' – user3770489 Feb 24 '16 at 10:27
  • no,the situation is i get 8 frames with the default threshold for scenecut detection.as the key frames i get is not representive enough .so i want to turn down the threhold to get more key-frames.but i use the -g and -sc_threshold arguments in my command(reference:http://stackoverflow.com/questions/14117757/how-to-control-key-frame-generation-of-ffmpeg) ,it donot work well.i still get the same 8 frames without any change.any ideas? – xinwei he Feb 24 '16 at 12:17
  • There seems to be a misunderstanding here. In an encoded video stream, a stored frame is either a keyframe or it isn't. You can't designate other frames to be treated as keyframes. The command in the original version of your Q will extract all I-frames. Those may not match your intuition of which frames ought to be keyframes, since the encoder may have decided otherwise. – Gyan Feb 24 '16 at 13:29

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You could output an iframes list and use it with some script.

$ ffprobe -show_packets -print_format compact input.mkv 2>/dev/null | egrep -n flags=K | cut -d: -f 1 > iframes
Geyslan Gregório
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