This paper studies the quality of multimedia content at very low bitrates. We carried out subjective experiments for assessing audiovisual, audio-only, and video-only quality. We selected content and encoding parameters that are typical of mobile applications. Our focus were the MPEG-4 AVC (a.k.a. H.264) and AAC coding standards. Based on these data, we first analyze the influence of video and audio coding parameters on quality. We investigate the optimal trade-off between bits allocated to

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... o and to video under global bitrate constraints. Finally, we explore models for the interactions between audio and video in terms of perceived audiovisual quality.