CODEWITHSUNDEEP
ffmpegmp4
Thomas
Thomas

Reputation: 12107

mp4 files / SSTS info

I am trying to find the fastest way to get a list of all I-frames in a movie.

So far, I tried ffprobe, but it is quite slow and I have been looking for a faster solution.

The other option I found is using the mp4parser tool; it outputs a file with this sectio, the SSTS info:

-------------------------------------------------------------------------
/moov/trak/mdia/minf/stbl/stss                              @ 0x1c152d8
  Box size: 0x44    version: 0x0    flags: 0x0
  entry_count:              0xd
    sample_number:
     0x1    0x12d    0x259    0x385    ....

I can see that I have 13 I frames and they're spaced 300 frames apart (from the 4 values displayed)

Is the spacing of I frames constant through movies? or do I need to write my own SSTS parser to get the whole list?

Upvotes: 1

Views: 799

Answers (1)

Gyan
Gyan

Reputation: 93038

The command below will quickly provide the timestamp for video keyframes along with other info.

ffmpeg -skip_frame nokey -i in.mp4 -an -vf showinfo -f null -

Output looks like

[Parsed_showinfo_0 @ 00000000032903a0] n:  55 pts:5748224 pts_time:449.08  pos: 17288779 fmt:yuv420p sar:1/1 s:960x720 i:P iskey:1 type:I checksum:361866A6 plane_checksum:[BA2DCCBF A8E937B3 BD006225] mean:[220 117 133] stdev:[57.8 4.1 5.3]

The pts_time gets you the time index. The n is not accurate for absolute frame index, but it is an accurate count for keyframe index i.e. n: 55 is the 56th keyframe in the video.

Upvotes: 1

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