Add enums for processing compressed videos from MPE rigs

[bjhardcastle]

Videos from legacy MindScope rigs are already sufficiently compressed but require colorspace/gamma adjustments and video metadata.

This PR:

• adds settings for that match GAMMA_ENCODING_FIX_INPUT_COLOR, without additional compression, using -c:v copy rather than -c:v libx264
• adds enums for consistent behavior across all uploads of these videos

@galenlynch - does this look necessary and correct? (I don't seem to have permissions to add reviewers)

[galenlynch]

This will not work, -c:v copy will copy the compressed video packets, which means you cannot change their values, including the pixel values. If you change the pixel values the video must be decompressed, adjusted, and then recompressed. The amount of compression of the input video is irrelevant.

[galenlynch]

I would suggest reducing the amount of compression happening on the rig, or instead doing all of your processing on the rig. However, the loss of visual quality to compress the video twice even if you can't (or won't) adjust the acquisition settings probably won't be a big problem, so you could just use the existing preset as is.

[bjhardcastle]

Thanks. We'll see about adjusting on the rig. The visual quality isn't affected too badly, though some loss of fine detail noticeable on areas like fur. And the file size is 10-25% larger after running with the existing preset.