Getting Source Timecode of Asset Clip in Timeline

[latenitefilms]

Following on from the discussion in TheAcharya/MarkersExtractor#81, I'd love to work out how to test DAWFileKit in a very specific situation so that I can update the FCP Cafe explanation/documentation here.

If I have the following FCPXML:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fcpxml>

<fcpxml version="1.11">
    <resources>
        <format id="r1" name="FFVideoFormat1080p24" frameDuration="100/2400s" width="1920" height="1080" colorSpace="1-1-1 (Rec. 709)"/>
        <asset id="r2" name="Test Clip - 25fps - 01-02-03-04" uid="F03C4D168FE7934996E6408D973FFB97" start="9307900/2500s" duration="60s" hasVideo="1" format="r3" hasAudio="1" videoSources="1" audioSources="1" audioChannels="2" audioRate="48000">
            <media-rep kind="original-media" sig="F03C4D168FE7934996E6408D973FFB97" src="file:///Folder/Test%20Clip%20-%2025fps%20-%2001-02-03-04.mov"/>
        </asset>
        <format id="r3" name="FFVideoFormat1080p25" frameDuration="100/2500s" width="1920" height="1080" colorSpace="1-1-1 (Rec. 709)"/>
    </resources>
    <project name="24fps Timeline" uid="99AB3F85-FDA0-49CD-83BB-B663A0F6FEA9" modDate="2024-02-10 06:02:11 +1100">
        <sequence format="r1" duration="12000/1920s" tcStart="7148480/1920s" tcFormat="NDF" audioLayout="stereo" audioRate="48k">
            <spine>
                <asset-clip ref="r2" offset="7148480/1920s" name="Test Clip - 25fps - 01-02-03-04" start="93079/25s" duration="12000/1920s" format="r3" tcFormat="NDF" audioRole="dialogue">
                    <conform-rate srcFrameRate="25"/>
                </asset-clip>
            </spine>
        </sequence>
    </project>
</fcpxml>

How can I use DAWFileKit to get the source timecode of the asset-clip at the timeline/project time of:

01:02:08:07 / 3728.29 seconds / 89479 frames

Looking in Final Cut Pro's Source Timecode display (and my burnt-in timecode) I know the answer is:

01:02:08:02 / 3728.08 seconds / 93202 frames

How can I reproduce this using DAWFileKit?

[orchetect]

I don't quite understand the question. Do you mean you want to know what clip intersects an arbitrary timecode?

[orchetect]

Not sure I follow yet. Given an absolute timecode, you want to know what the asset-clip's local timeline timecode is for it?

Since this example has different frame rates (24fps project, 25fps asset), you can read timecode from DAWFileKit either using the top-level frame rate (project rate) or the clip's local frame rate.

DAWFileKit's default is to use the top-level timeline's context. So it would give you timecode as 24fps by default.

[latenitefilms]

Basically when I originally posted this, and was adding the documentation to FCP Cafe, I was attempting to use DAWFileKit for my Metaburner project. In the end we decided not to go down the DAWFileKit route, and use our own proprietary FCPXMLKit implementation - which the jury is still out on whether or not that was a silly idea, as we've basically had to go through all the same chaos and problem-solving as you've had to solve in DAWFileKit.

What we do is essentially loop through every frame on the timeline/project, and collect information about all the clips at that frame.

In this case, I wanted to "feed in" the timeline/project value (i.e. 01:02:08:07 - although we'd most likely be feeding in CMTime of a fractional value, as opposed to "timecode"), and "collect" all the metadata for the clips at that timeline/project frame. In this case, we only have a single asset-clip, and we want to get the clip's source/local timecode value in it's source/local frame rate - i.e. 01:02:08:02 @ 25fps.

The reason this example has a 24fps timeline/project and a 25fps clip is because I wanted to make sure we're actually getting the clip's local/source timecode at the clip's local/source frame-rate.

We've since got this working pretty well in our own FCPXMLKit - however there's definitely still edge cases where things are a bit funky, for example, in the below screenshot the timecode is perfect, EXECPT for this "segment" that has Normal 100% speed, the source timecode is one frame off.

[orchetect]

Certainly possible with DAWFileKit but I'd probably have to built out a new extraction paradigm based on time and not objects. Basically something that could build an internal model of time ranges and objects in those ranges with a given timeline context (which would be main timeline by default). Then it would be trivial to feed it an arbitrary time and get back everything that intersects at that time. I could see it being a useful feature.

[latenitefilms]

That would be amazing!

I believe that's kinda what we're doing now - we have FCPXMLReport, we adds reporting capabilities to our FCPXMLKit framework.

For me to consider switching to DAWFileKit though would require a lot more additions to DAWFileKit because we need to access video inspector parameters (taking into account keyframes), stabilisation, etc. DAWFileKit would basically need to have access to everything that the current DTD supports, which is a lot of work.

I'm also not sure DAWFileKit takes into account speed changes (timeMap) in its current implementation, which is required (and bloody tricky!) when trying to get source timecode from a Multicam Clip with a speed effect, which contains a Sync Clip with a speed effect which contains an Asset Clip with a speed effect, etc (let alone the conform-rate stuff too!).

FCPXML is the devil, haha.

[orchetect]

That's totally fine. Like a lot of open-source, DAWFileKit is a labor of love and new features are generally added as-needed. Use whatever works for you.

not sure DAWFileKit takes into account speed changes (timeMap) in its current implementation

No, it's on the list of things to-do of course.

I like the notion of making clear distinction between the XML model and reasoning/reporting on the data. Right now all the API intermingle in the library but I can see making that more clear.