A method includes: receiving a script configured to modify the audio-video file; calculating a performance metric based on execution of the script on a set of test files; classifying the script as performant based on the performance metric; defining a metadata store associated with the script and the audio-video file; receiving a playback request specifying a rendition of the audio-video file from a computational device; in response to receiving the playback request: accessing a set of data inputs from the metadata store; executing the script on a frame of the audio-video file based on the set of data inputs to generate a modified frame of the audio-video file; transcoding the modified frame of the audio-video file into the rendition to generate an output frame of the audio-video file; and transmitting the output frame of the audio-video file to the computational device for playback at the computational device.