Handling of the ffmpeg dependency

[superseed]

I just started using this package, trying out an example from a blog post that uses both Gizeh and MoviePy.

When I executed the first example, a download started for ffmpeg, followed by an error about the requests package missing from the env. This second problem seems to have been resolved with 006b376 however (though I would suggest to use urllib from the standard lib for this single HTTP request to avoid a new dependency, but that's not the point of the issue).

The thing is that I do have ffmpeg installed and up-to-date and getting a binary downloaded in my home dir without asking feels wrong to me. I would have preferred the application to error out on not finding the binary. I looked at the README in the repo and saw that I could set the binary location in config_defaults.py, so I tried that but it didn't change anything (i.e. it kept downloading ffmpeg). I looked around the code to find that since b8fcf45, the environment variable FFMPEG_BINARY is checked on import of editor.py and if unset or equal to ffmpeg-imageio, is downloaded through imageio's primitives.

I see three problems with this approach:

• It checks the environment variable FFMPEG_BINARY instead of the global python variable defined in config_defaults.py, which is unwieldy anyway since it's a build-time conf (aka a 'sneaky edit in the lib/python* directory' type of conf). However note that setting the environment variable to the binary's path before using the package does work! It's just kinda undocumented.
• It doesn't really check for ffmpeg by itself, which is the bigger pain point.
• When it doesn't find it, it tries downloading it by itself.

There a few potential solutions:

• Keep things this way and document the need to set the environment variable, maybe homogenize the behavior by using the environment var everywhere else
• Check the variable set in config_defaults.py instead of the environment variable
• Allow for a runtime configuration file somehow
• Actually check for a valid ffmpeg binary. To me this is the better solution: it can be done easily -- check if it is available in the PATH with shutil.which('ffmpeg'), possibly subprocess.run() it to get the version number and check compatibility. If it's not found, two possibilities:
  • Download it to the homedir automatically (and get frowned upon by me 😄)
  • Error out with a warning and handy tips for the user. Possibly with a lot of user-friendliness, e.g. ship a little script with the MoviePy package linked to a console_scripts entry in setup.py to setup the needed dependencies.

Does any of this sound reasonable? I could send a PR your way if you think it could be useful.

(This package and Gizeh are really good, by the way! 🎉)

[tburrows13]

It is all rolled into imageio_ffmpeg now, so hopefully not an issue.