i-vid: video file input via ffmpeg

the i-vid module uses ffmpeg's backend libraries (avcodec/avformat) to read compressed video streams as input.

parameters

colour colour space of the input video
trc tone response curve in the encoding
bitdepth bit depth of the input video stream (actually immutable but displayed here for your information)
chroma subsampling of the chroma planes (actually immutable but displayed here for your information)
colrange the colour range (full or restricted)