Loudness and auditory masking compensation for mobile TV

Quality of Experience in mobile multimedia services is subject to environmental changes. Especially in urban environments, several types of background noises affect the perceived quality of audio content, and the characteristics of noise can rapidly change within a few minutes of travel. Also, the change of loudness in the multimedia content itself can be annoying - users will have to adjust volume settings for each specific content type when there is a high dynamic loudness behaviour. It is therefore necessary to automatically adapt the audio playback to the environmental conditions by implementing several methods and testing them. To develop these methods, the impact of environmental noise on the subjective setting of volume needed to be studied by performing a first experiment with human observers. Then, various processing schemes were applied to the audio tracks. These include the decreasing of available headroom as a simple mean of dealing with high loudness dynamics, but also multiband compression alongside noise-specific equalization, which can be used for complex content types such as classical music. Their effect on users perception has been studied by performing two additional user studies.