Recommendation: Release this to work with video file input and output

[richardpickett]

It'd be nice to feed an already-recorded video through this to remove the background.

[BenBE]

While the current code structure is quite fixed on reading the video stream from the V4L video device it shouldn't be too hard, implementing a different processing mode for the input/output, once Something like #38 and #41 are implemented (amongst some other code structure changes).

[phlash]

This is a similar need to the one I had for animated backgrounds, the separated input module I have (https://github.com/phlash/deepbacksub/blob/65c7f4a8f0f5ddd1cfc6305fef825690fc1a1931/capture.cc#L59) allows local files to be used as source material for either input stream. This supports @BenBE's statement that it's not too hard, and for me points towards doing one thing well (segmentation and mask generation), with other features (background substitution, offline processing, etc.) perhaps delegated to existing machinery (eg: ffmpeg, obs)?