Apple wants the volume levels to be more consistent when playing your music on OS X or iOS device. The company has been granted a patent (number 9,240,7638) by the U.S. Patent & Trademark Office for “loudness normalization based on user feedback.”
The music industry produces audio content at various loudness levels. Apple says this lack of an established standard during production provides a poor user experience when randomly playing back content produced by different entities, produced for different albums, and/or content of different genres as loudness levels may wildly fluctuate.
The normalization system includes a content delivery system for a variety of audio playback devices. The audio playback devices may communicate volume settings used during playback of pieces of sound program content to the content delivery system. Based on these collected data points, a “statistical analysis” may be performed to generate loudness adjustment values for pieces of sound program content.
Per Apple’s invention, each of your audio playback devices may adjust volume settings while pieces of sound program content are being played on each device. The adjustments may be made by users of each corresponding device so that a preferred loudness is achieved. The audio playback devices may communicate these user adjusted volume settings used during playback of each piece of sound program content to the content delivery system.
The transmission of volume settings to the content delivery system may include data regarding the playback configuration on corresponding audio playback devices. Based on these collected data points, a statistical analysis may be performed to generate loudness adjustment values for pieces of sound program content.
The loudness adjustment values may be communicated to audio playback devices through metadata in associated pieces of sound program content or as separate communications from the content delivery system (which I’m sure Apple expects to be iTunes running on your Mac, iPhone, iPad, Apple Watch, Apple TV, or iPod touch). These loudness adjustment values may thereafter be used to adjust loudness of the pieces of sound program content played on the audio playback devices.
The invention also provides for an offline version of the loudness normalization system that supports individual loudness normalization adjustments based on a single user's preferences. Under either embodiment, loudness normalization may be achieved based on real world volume settings for individual pieces of sound program content played using various playback configurations.