4

I am using ffmpeg to extract frames from videos. I have the following code thus far:

ffmpeg -i vid.mp4 -vf fps=1/10 images%05d.png

My issue is that it takes awhile! 6 seconds per image on average. Is there a way to speed this up? I am working with tens/hundreds of videos and I'm wanting to write up a shell script to automate the whole thing, but I don't want it to take days!

I have seen other programs that can do this but they have to literally play through the video to reach the frames to extract. That would be far too slow. Perhaps ffmpeg is doing something like this?

Any ideas how to speed this up?

The videos at hand are 1920x1080 GoPro videos and I'd like full resolution images.

Here's the output from the console:

ffmpeg version 2.7.2 Copyright (c) 2000-2015 the FFmpeg developers
  built with Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)
  configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-avresample --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libspeex --enable-libass --enable-libbluray --enable-lzma --enable-gnutls --enable-fontconfig --enable-libfreetype --enable-libfribidi --disable-indev=jack --disable-outdev=xv --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/clang --enable-vda --arch=x86_64 --enable-yasm --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid --enable-nonfree --enable-libfdk-aac --enable-libfaac
  libavutil      54. 27.100 / 54. 27.100
  libavcodec     56. 41.100 / 56. 41.100
  libavformat    56. 36.100 / 56. 36.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 16.101 /  5. 16.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.100 /  1.  2.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'vid.mp4':
  Metadata:
major_brand     : mp42
minor_version   : 1
compatible_brands: mp41mp42isom
creation_time   : 2015-09-18 03:38:20
  Duration: 00:01:18.23, start: 0.969178, bitrate: 20388 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 20004 kb/s, 29.97 fps, 29.97 tbr, 180k tbn, 59.94 tbc (default)
Metadata:
  creation_time   : 2015-09-18 03:38:20
  handler_name    : Core Media Video
  encoder         : GoPro AVC encoder
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 127 kb/s (default)
Metadata:
  creation_time   : 2015-09-18 03:38:20
  handler_name    : Core Media Audio
[swscaler @ 0x7fdb12000000] deprecated pixel format used, make sure you did set range correctly
Output #0, image2, to 'images%05d.png':
  Metadata:
major_brand     : mp42
minor_version   : 1
compatible_brands: mp41mp42isom
encoder         : Lavf56.36.100
Stream #0:0(und): Video: png, rgb24, 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 0.10 fps, 0.10 tbn, 0.10 tbc (default)
Metadata:
  creation_time   : 2015-09-18 03:38:20
  handler_name    : Core Media Video
  encoder         : Lavc56.41.100 png
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> png (native))
Press [q] to stop, [?] for help
frame=    9 fps=0.2 q=0.0 Lsize=N/A time=00:01:30.00 bitrate=N/A    
video:17647kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
3

I have no idea if what you're doing is optimal, but "playing the video" to extract frames is essentially what has to happen, at least a little, if the frame you're extracting is not an I-frame (most frames are not).

The chosen frame is likely represented as the accumulated differences since the last complete frame, which is what interframe compression does. In order to extract it, a program must read and reconstruct the intervening frames -- not from the beginning of the video, just from the most recent complete frame

Depending on how many frames you need from each video, it might make sense to first convert to an "all-I" codec like MJPEG, where every frame stands alone. Then extracting any given frame would be much faster. When done you can delete the converted file.

  • 1
    I think the bottleneck here is frame seeking rather than decoding. Try encoding a file in ffmpeg from a mid-point in the source (-ss 2400 or 40 minutes in) and ffmpeg will take some time to get going. Whereas on modern silicon, software players easily decode and process 24-30, if not 60, frames per second to provide realtime playback. That said, converting to I-frame only codec is the right way forward. – Gyan Sep 18 '15 at 16:17

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