Post-production is not permitted in changing the clips as seen from the render directly from Unreal Engine. There are ways to add audio, whether sound effects or music, to your render. Please refer to the documentation. That being said, adding audio directly to the render via post-production is the only permitted use of post-production for UE entries providing the footage remains unchanged. Please see the following FAQs
Can I use Movie Render Queue?
Your video file must be encoded directly from Unreal Engine only, using any methods described in the documentation, including Movie Render Queue. We reserve the right to ask you to provide a screen recording of running the render from Movie Render Queue.
Can I use audio or dialogue?
Yes, but be advised that it is not a part of the judging criteria. If you use post-production software, you may ONLY use it for adding audio, and not to manipulate the visuals in any way; we reserve the right to ask to see a screen recording of the render within Unreal Engine. You can also add audio from within the engine using the command-line encoder (in the case of Movie Render Queue) or by adding audio tracks via Sequencer.
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