Use FFmpeg to Capture I Frames of Video
First we need to download ffmpeg.exe from: http://ffmpeg.zeranoe.com/builds/
Use the commands below to extract all key frames (I, P, B) and their corresponding timecodes:
On Linux, it can be an one-off accomplishment:
ffmpeg -i yourvideo.mp4 -vf select="eq(pict_type\,PICT_TYPE_I)" -vsync 2 -s 160x90 -f image2 thumbnails-%02d.jpeg -loglevel debug 2>&1 | grep "pict_type:I -> select:1" | cut -d " " -f 6 - > ffmpeg_decode-info.txt
On Windows:
ffmpeg.exe -i yourvideo.mp4 -vf select='eq(pict_type\,I)' -vsync 2 -s 160x90 -f image2 thumbnails-%02d.jpeg -loglevel debug 2>&1 | findstr "pict_type:I" > ffmpeg_decode_info.txt
Now we will get a text file filled with formated text lines like:
\[Parsed_select_0 @ 05253d60\] n:134.000000 pts:135000.000000 t:5.400000 key:1 interlace_type:P pict_type:I scene:nan -> select:1.000000 select_out:0
Since we need only I frames’ index, we can split each text line and get the target columns:
(for /f "tokens=5 delims= " %i in (ffmpeg_decode_info.txt) DO echo %i) > ffmpeg_iframe_index.txt
(Note: the file name “ffmpeg_decode_info.txt” should not contain any space.
Otherwise we should add another option usebackq:
(for /f "usebackq tokens=5 delims= " %i in ("ffmpeg decode info.txt") DO echo %i) > ffmpeg_iframe_index.txt
)
Sometimes we would find some strange lines insert to ffmpeg_decode_info.txt (I don’t know what it means, its insert location even whether it is inserted or not is unpredictable)
frame= 57 fps=2.7 q=2.1 size=N/A time=00:00:54.01 bitrate=N/A speed=2.56x
Conflict will appear if we don’t add some special handling. Usually this line is appended with the normal text line that we need, just like below:
frame= 57 fps=2.7 q=2.1 size=N/A time=00:00:54.01 bitrate=N/A speed=2.56x **\r**\[Parsed_select_0 @ 05253d60\] n:134.000000 pts:135000.000000 t:5.400000 key:1 interlace_type:P pict_type:I scene:nan -> select:1.000000 select_out:0
Split it by \r will be Okay.
Reference
http://forum.doom9.org/archive/index.php/t-163553.html
