adding private UPID parsers

[richard-vd]

Hi Adrian,

I would like to add two private UPID parsers to threefive, based on this spec: https://mediaperspectives.nl/app/uploads/2020/03/2020-12-22-Media-Perspectives-ETDSS.pdf

Here is my attempt for the SBSB UPID: richard-vd/bitn@75c0a5a and richard-vd/SCTE35-threefive@b63110a

Comments are welcome, is this the way to go?

This is the output:

"descriptors": [
    {
        "tag": 2,
        "descriptor_length": 63,
        "identifier": "CUEI",
        "name": "Segmentation Descriptor",
        "segmentation_event_id": "0x0",
        "segmentation_event_cancel_indicator": false,
        "components": [],
        "program_segmentation_flag": true,
        "segmentation_duration_flag": false,
        "delivery_not_restricted_flag": true,
        "segmentation_message": "Content Identification",
        "segmentation_upid_type": 12,
        "segmentation_upid_length": 48,
        "segmentation_upid": {
            "MPU": {
                "format identifier": 1396855618,
                "SBSB": {
                    "private_cni": "0x361f",
                    "private_version": 1,
                    "private_transmission_id": 695029162812,
                    "private_product_code": 1214932,
                    "private_web_publication_key": "SJMOuNsL4K3"
                }
            }
        },
        "segmentation_type_id": 1,
        "segment_num": 0,
        "segments_expected": 0
    }
]

[futzu]

Good idea,
Since it's "custom" handling, it doesn't really belong in the lib.
I think something like this keeps it flexible for other custom upid handlers

https://github.com/futzu/threefive/blob/master/examples/upid/custom_upid_handling.py