Include napari version information in output video metadata

[GenevieveBuckley]

Description

Companion to PR napari/napari#5494

This adds a digital watermark to the video files output by napari-animation. That means in the future it may be possible to scrape publications & supplementary data, eg: like this analysis done for matplotlib https://github.com/mrocklin/arxiv-matplotlib

Try it out!

Now, you can run the examples to create a video file:

python napari-animation/examples/animate2d.py

...and then look at the metadata embedded in the video file header with ffmpeg. This ffmpeg command writes the metadata to a text file:

!ffmpeg -i demo2d.mov -f ffmetadata FFMETADATAFILE.txt

And when you look at the output

cat FFMETADATAFILE.txt

...you see something like this (note the new "title" metadata field, which was not there before:

;FFMETADATA1
major_brand=qt  
minor_version=512
compatible_brands=qt  
title="napari version 0.4.17 https://napari.org/"
encoder=Lavf59.27.100

Actually, here is a simpler way to read the metadata from the video file:

    # Read metadata back in, and check for napari version information
    # We expect to see a metadata line in the metadata like this:
    # title="napari version 0.4.17 https://napari.org/"
    with open(output_video_filename, 'rb') as f:
        content = f.read()
    assert b"napari version" in content
    assert b"https://napari.org" in content

Additional details

I have stuffed the napari version information into the "title" metadata key, because that seems to be the most widely available. (.mp4 files do allow a "description" metadata field, but that is not supported by .avi, .mov, and possibly many other file formats).

[codecov]

Codecov Report

Merging #167 (3ad70f0) into main (d8bd609) will increase coverage by 0.90%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #167      +/-   ##
==========================================
+ Coverage   85.31%   86.22%   +0.90%     
==========================================
  Files          24       26       +2     
  Lines         926      987      +61     
==========================================
+ Hits          790      851      +61     
  Misses        136      136              

Impacted Files	Coverage Δ
napari_animation/_tests/test_animation.py	100.00% <100.00%> (ø)
napari_animation/animation.py	87.25% <100.00%> (+0.38%)	⬆️

... and 3 files with indirect coverage changes

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[GenevieveBuckley]

I notice that the other tests (like test_animate_filenames above) are very careful to mock/patch the video writer, so I'm not sure if you won't like that it actually runs here.
I'm not really sure how best to test this without generating real output video files though.

[alisterburt]

I think this is okay, that was done because the output wasn't being checked for anything afaik

[GenevieveBuckley]

Link to a notebook I used while I was figuring this out: https://gist.github.com/GenevieveBuckley/72e438539ab03c792d52040ccb9e8f02

The trick was, you need to SEPARATE the "-metadata" string from the "title=MyTitle" string in the output_params list that gets passed in to imageio_ffmpeg.

        output_params = ["-metadata", f'title="{description}"']

It will NOT work if you pass it all as one string, eg: output_params=["-metadata title=MyTitle"]

Plus, you just extend the idea if you want to pass in more metadata keys. The only problem is, not many metadata keys are supported by a wide variety of file formats.

output_params = [
    "-metadata", f'title="My Title"',
    "-metadata", f'description="Description goes here"',  # description metadata supported by .mp4, but not .mov, .avi, and possibly many other file formats
]

[alisterburt]

Cool! thanks for the PR - made a tiny change so there wasnt a spurious reference to __version__ within the package but otherwise this is great!

[alisterburt]

I think this is okay, that was done because the output wasn't being checked for anything afaik

[GenevieveBuckley]

Thanks for the review!