Fix indeterminate z-order of EditedMediaItemSequences

[AradiPatrik]

Root Cause:

The indeterminate z-order issue arises due to the non-deterministic loading of assets. As each asset finishes loading, DefaultVideoCompositor.registerInput is invoked, linking the z-order to the unpredictable asset loading sequence. Consequently, the final z-order in the output is uncertain, as it's contingent on the load completion sequence of the assets.

Proposed Fix:

To resolve this, I've explored two options:

• Option A: Modify TransformerInternal.java to aggregate all loaded assets first, then sequentially invoke registerInput in the intended order.
• Option B: Introduce a sequenceIndex parameter to registerInput, decoupling the z-order from the invocation sequence and aligning it with this index instead.

Implemented Solution:

I opted for Option B due to its straightforward implementation. Post-fix, the z-order issue was no longer reproducible, indicating the effectiveness of this solution.

Links

• Original issue
• Simple Sample Project for reliable reproduction

I'm open to feedback and willing to assist further to ensure a robust resolution to this z-order inconsistency.

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[dway123]

Thank you for the quick PR! I'll try to take a look in the next few days. Also, cc @claincly who is pretty familiar with these files too

[dway123]

I have less familiarity than @claincly here so I'll defer to him, but just noting that without as much context, I think the general option B selected in this PR sounds good to me (haven't looked to make sure the implementation style/architecture makes sense though). Option A would also require adding additional state and/or blocking, so I'd prefer B over A.

[AradiPatrik]

@claincly I implemented the changes you requested. Please take a look and resolve it if it's OK. Let me know if there's anything else we need to change before this PR can be merged.

[claincly]

I'm going to send this for internal review now. You may see some more commits being added as I make changes in response to review feedback. Please refrain from pushing any more substantive changes as it will complicate the internal review - thanks!

[AradiPatrik]

@claincly Any updates on this? Can I assist in any way?

[claincly]

Hey Aradi, we are discussing it internally as it's an API change, will keep you in the loop!

[yuriikonovalov]

@claincly could you provide some information (if it's possible) when it potentially can be merged and released so that this fix is available to use in production?

[droid-girl]

The CL is still in review. We will try get back to you with a status update shortly