Extract all key frames from a video using ffmpeg tool

[Benoit Fouet]

I've been asked several times if we could make the ffmpeg command line tool able to extract all key frames from a video.
I don't think it's possible today, but may be a nice feature to have.

[Stefano Sabatini]

Addressed in commit:

commit 07586b68a8a496e44c7c977599e1ec09d07fd57f
Author: Stefano Sabatini <stefano.sabatini-lala@poste.it>
Date:   Sat May 7 02:06:25 2011 +0200

    lavfi: add select filter
    
    Address trac issue #92.

You can use the filterchain:
-vf select="eq(pict_type\,PICT_TYPE_I)"

for selecting only the I-frames to send to the output.

Note that you'll have still to decode all frames, since we currently don't have a packet-level filtering mechanism.

[lovelove]

cross-reference: #442 (scene change detection)

[lovelove]

[As a reference for other users:] As kindly explained by Stefano Sabatini, the abovementioned -vf parameter needs to be coupled with the -vsync 0 parameter if one wants to "extract all key frames from a video" without duplicates, as is the idea behind this ticket.