Why Composition buildUpon() method is package-private?

[muhammad-najam-cmp]

I’m working with Media3 Transformer (v1.7.1) along with Composition, and my use case is split into two parts:

1. Preview / runtime playback – I use CompositionPlayer to preview video with basic overlays.
2. Export / final output – I use Transformer to export video, but here I need to add additional values

The problem:

For preview, I build a Composition without heavy overlays.

For export, I would like to reuse the same Composition but extend it with extra overlays.

I noticed that Composition has a method:

/* package */ Builder buildUpon()

But it’s package-private, so I cannot call it.
This forces me to rebuild the Composition completely for export, which duplicates logic and is error-prone.

I also confirmed that the preview Composition works fine with Transformer, but since it doesn’t contain the extra overlays, the export misses them.

Question

Is there a recommended way to:

1. Reuse an existing Composition for export,
2. Add or modify only the overlays/effects,
3. Without fully reconstructing the Composition?

Or is there a plan to make buildUpon() (or a similar API) public so that developers can safely clone and extend an existing Composition?

[droid-girl]

Hi @muhammad-najam-cmp,
Thank you for your question. At the moment, for your use case, we recommend re-creating your composition every time.
I will mark this as a feature request and it is on our backlog