CMX 3600 does not handle correctly transitions

[gplsteph]

Bug Report

Incorrect Functionality and General Questions

CMX 3600 reads everything in an EDL as Clips and then perform a conversion to Transitions when needed. However, instead of keeping the Clip before the transition (in the EDL), it removes it from the Timeline and keeps the Clip for the EDL transition, loosing meta data and possibly media for Clip at the end of the transition (in the timeline).

To Reproduce

Load the following EDL:

TITLE:   OTIO_TEST
FCM: NON-DROP FRAME

001  ABC0100 V     C        01:00:00:00 01:00:01:00 01:00:00:00 01:00:01:00
* FROM CLIP NAME: shot_001_v001
* COMMENT: shot_001

002  ABC0200 V     C        01:00:01:00 01:00:01:00 01:00:01:00 01:00:01:00
* COMMENT: shot_002

002  ABC0200 V     D    024 01:00:01:00 01:00:02:00 01:00:01:00 01:00:02:00
* FROM CLIP NAME: shot_001_v001
* TO CLIP NAME: shot_002_v001

003  ABC0300 V     C        00:00:05:00 00:00:15:00 01:00:02:00 01:00:12:00
* FROM CLIP NAME: shot_003_v001
* COMMENT: shot_003

note: The last entry is needed because of another problem with the cmx 3600 adapter when the last entry is a transition.

edl_timeline = otio.adapters.read_from_string(edl_text, adapter_name="cmx_3600")

Check the result by looping over children:

for child in edl_timeline.tracks[0]:
    logger.info("Child %s" % child)

This gives:

Clip("shot_001_v001", MissingReference('', None, {}), TimeRange(RationalTime(86400, 24), RationalTime(36, 24)), {'cmx_3600': {'comments': ['COMMENT: shot_001'], 'reel': 'ABC0100'}})
Transition("shot_002_v001", "SMPTE_Dissolve", RationalTime(12, 24), RationalTime(12, 24), {'cmx_3600': {'reel': 'ABC0200', 'transition': 'D', 'transition_duration': 24.0}})
Clip("shot_002_v001", MissingReference('', None, {}), TimeRange(RationalTime(86436, 24), RationalTime(12, 24)), {'cmx_3600': {'reel': 'ABC0200', 'transition': 'D', 'transition_duration': 24.0}})
Clip("shot_003_v001", MissingReference('', None, {}), TimeRange(RationalTime(120, 24), RationalTime(240, 24)), {'cmx_3600': {'comments': ['COMMENT: shot_003'], 'reel': 'ABC0300'}})

The Clip after the Transition has wrong meta data, since it is the Clip which was created when reading the EDL, before treating transitions. The same would apply for media reference if there was some.

Expected Behavior

The Transition should be inserted between the Clips contributing to the transition, and those Clips should be kept, with just their time range adjusted.