It seems like you're referring to a file format, specifically an MP4 video file, possibly related to "Polly," which might be Amazon Polly, a text-to-speech service. MP4 files are commonly used for video content, and while Polly primarily generates audio, you can use it to create audio files that may then be integrated into video projects.
If your intention is to create an MP4 that contains audio generated by Amazon Polly, you'll need to:
1.