I2S Output from Wav File

[rhvarrier]

I'm trying to get a Wav file to play over I2S (connected to a MAX98357A audio amp).
Here is the relevant code snippet. The implementation is very similar to i2s output sample

The test WAV file that I'm using is a recording of a single beep sound. However all I'm getting at the output is a distorted burst.
Has anyone tried to do something similar ? Do I need to use a zephyr audio codec to get the output.
I couldn't find any relevant samples or documentation about this use case and zephyr's audio support documentation seems incomplete.