Input media data with an input playing speed is received and divided into input media data subsets. A first rate of audio utterance is determined for a first input media data subset in the media data subsets. A second different rate of audio utterance is determined for a second input media data subset in the media data subsets. Audio output media data is generated with an output playing speed at which audio utterance in the audio output media data is played at a preferred rate of audio utterance. The audio output media data comprises (a) a first output audio media data subset generated based on the preferred rate, the first rate, and the first input media data subset and (b) a second output audio media data subset generated based on the preferred rate, the second rate, and the second input media data subset.