[FFmpeg-user] essence MD5 for still images

[Carl Eugen Hoyos]

2018-01-06 20:38 GMT+01:00 *** <gli7676 at gmail.com>:

> Somewhere I discovered that ffmpeg will create essence
> MD5s for supported still image formats.

And audio and video.
(From FFmpeg's pov, an image format is a video format.)

> I began using the following command to verify that
> the image essence did not change in photos after
> their IPTC metadata is revised.

> Because there is no documentation of such a use case
> on the ffmpeg site nor anywhere else on the web I have
> begun to doubt that this is a valid use of ffmpeg or this
> command.

Different possibilities exist within FFmpeg to calculate
checksums, the FFmpeg regression tests are a usage
example.

> Is anyone else doing this?

Many people are.

> Even if you aren’t I would appreciate any comments or
> observations that you care to share.
>
> ffmpeg -i INPUT -map 0:v -f md5 OUTPUT.md5

This command line will calculate the md5sum of the first
video stream in the input file.
You may want to look at the framemd5 muxer for other
use-cases, other algorithms also exist.

Carl Eugen