[FFmpeg-devel] [PATCH 0/1] New helper expr for the select filter

Michael Niedermayer michael at niedermayer.cc
Wed Feb 7 02:49:04 EET 2018


On Mon, Feb 05, 2018 at 04:48:44PM -0500, bmathew at gmail.com wrote:
> Added a new expr/function get(n, filename) in libavutil/eval.c that is meant to
> be used in conjunction with the select filter and greatly enhances the
> generality of the select filter.
> The select filter as it exists now can be used to selectively enable frames
> during transcoding.  e.g.: select='not(mod(n\,100))' will enable one frame every
> 100.
> It is often required to do much more complex frame by frame selection under the
> control of an external program. For example, a face detector might indicate
> frames on which certain individuals have been detected and we wish to get a
> video with only frames where those individuals are present. Another example is
> video of lab experiments synchronized with some external sensor and we wish to
> extract the frames where the sensor detected some event.
> The get operator may be used as follows:
> -vf 'select=get(n\,"frame_select.en")'

no, this is not secure

if you want to pass data from a file to a expression this has to be done in a
way different from the eval code taking a filename from its expression string.

also data should be taken as 64bit double precission floats not bytes


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Avoid a single point of failure, be that a person or equipment.
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