readers.video - Sampling from a subset of frames

Hi. I want to achieve the following result, if possible.

SCENARIO
I am working on a project regarding faces. I have long (labeled) video footage of which only few segments are interesting. Maybe I have a face track from frame S1 to E1, then another face track from S2 to E2 and so on. I have big json file with all these tracks, and relative bounding boxes. Eg:

      [======= F1 =======]
      :            [====== F2 ======]
[-----|------------|-----|----------|-----] t
0    100          300   400        600   700

Then I have this info in the json:

100 -> BBox
101 -> BBox
...
350 -> [BBox, BBox]
...
450 -> BBox
...
600 -> BBox

EXPECTED BEHAVIOR
I want the video reader to return a batch where each sample is (frame, bounding box)

Tuple[NDArray, Tuple[int, int, int, int]]

• valid frames only (e.g. in the example above excluding range 0-99 and 601-700)
• one BBox. Or the full list, then I could randomly choose one of them.
  In this moment I am not interested into temporal ranges (that's the next step), just sequence length of 1 is fine.

Is there a way to achieve this?