Given the constraints of AVAssetWriter, the video file indeed cannot be played back until finishWriting has been called and the file is finalized. Unfortunately, this means that any attempts to preview the video file during the writing process will result in an incomplete or corrupt file.

Summary • No Direct Playback During Writing: Since the file is not finalized until after finishWriting, you cannot preview the video until this method has been executed.

Alternative Approaches

1. Use a Temporary Preview: Instead of directly previewing the video file being written, consider rendering a few frames of the video (or a still image) as a temporary preview using AVPlayer or a simple UllmageView.
2. Export to a Specific Location: Once the video is fully exported, you can then preview it. This means you'll have to wait until the entire process is complete.

Conclusion If you're looking for an approach to play the video during the encoding process, there isn't a viable option because of how AVAssetWriter works. You will need to wait until the writing is completed before the video can be played back successfully.