TimeUnit conversion helpers

[keighrim]

New Feature Summary

As a subtask to #206 , Id like to see addition of time unit conversion code in this package. A few things to consider implementation-wise;

• currently we use three units; frame, milliseconds, and seconds.
• there could be some alternative spellings of the units in use (some examples;
  • frames: frame
  • seconds: second, sec, s
  • milliseconds: millisecond, msec, ms
• for conversion from/to frames, code needs to know fps of the video, and there could be two possible sources of the information under the current specification
  • in the Annotation annotation this should be obtainable via something like this

  ann_v = mmif.get_views_for_document('vd1')
  ann_ann = ann_v.get_annotation(AnnotationTypes.Annotation)
  fps = ann_ann.properties['framerate']
  # again, there may be alternative keys ('frame-rate', 'frames-per-second', 'fps', ...)

  • from the video directly

  vd = mmif.get_document_by_id('vd1')
  vobj = cv2.VideoCapture(vd.location_path)
  fps = vobj.get(cv2.CAP_PROP_FPS)

  • note that the second method requires some video processing software under the hood (opencv, ffmpeg, etc), but I don't like to ship mmif-python package with a full opencv dependency. Hence we might need to consider implementing this part as a plugin package.

Related

#206 and remotely related to clamsproject/app-east-textdetection#1

Alternatives

We could just leave this implementation to app developers. Some existing code that does time unit conversion

1. as output unit

https://github.com/clamsproject/app-east-textdetection/blob/e7f2549fc875fd5c1762a3046de68ea67a82140d/app.py#L71-L81

2. as input unit

https://github.com/clamsproject/app-parseq/blob/7f4476775f708f8ee23aaad2dc3210d327b0f8c9/app.py#L27-L38

Additional context

No response