# Perceptual Quality of Audio-Visual Content with Common Video and Audio Degradations
###### Abstract  
Audio-visual quality assessment remains as a complex research field. A great effort is being made to understand how visual and auditory domains are integrated and processed by humans. In this work, we analyzed and compared the results of three psychophysical experiments that collected quality and content scores given by a pool of subjects. The experiments include diverse content audio-visual material, e.g., Sports, TV Commercials, Interviews, Music, Documentaries and Cartoons, impaired with several visual (britate compression, packet-loss, and frame-freezing) and auditory (background noise, echo, clip, chop) distortions. Each experiment explores a particular domain. In Experiment 1, the video component was degraded with visual artifacts, meanwhile, the audio component did not suffer any type of degradation. In Experiment 2, the audio component was degraded while the video component remained untouched. Finally, in Experiment 3 both audio and video components were degraded. As expected, results confirmed a dominance of the visual component in the overall audio-visual quality. However, a detailed analysis showed that, for certain types of audio distortions, the audio component played a more important role in the construction of the overall perceived quality. video quality assessment; audio and video quality; QoE +
Footnote †: journal: Applied Sciences  
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Footnote †: journal: Applied Sciences  
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(also known as perceptual or subjective experiments) [8]. Such experiments can be used to provide a measure of the level of influence that certain (audio and video) distortions have on the audio-visual quality perceived by human users. This information is key in the process of testing and developing objective quality metrics, now more than before, since quality metrics based in Machine Learning (ML) techniques are highly dependent on annotated data for training and testing new models [6; 9; 10; 11]. Psychophysical experiments are commonly carried out within a controlled environment (e.g., soundproof laboratories), where test stimuli (e.g., audio-visual sequences) is presented to a group of non-expert human participants (or experts depending on the application being studied). With the goal of generating reliable and reproducible results that represent quality as perceived by human users, several international agencies and research organizations have collected and published guidelines and recommendations on how to perform psychophysical experiments [8; 12; 13; 14; 15]. Although these recommendations are widely adopted and applied in most perceptual studies, they often limit the representation of an authentic user experience, which is a requirement in multimedia applications. For this reason, researchers have created novel methods to deal with this matter. For example, an immersive methodology proposed by [PERSON] [16] tried to recreate a more natural media consumption environment for a human consumer, thus, allowing to collect human responses that are more realistic and useful for a quality perception analysis. Quality perception of audio-visual signals has been studied thought several perceptual experiments [17; 18; 19; 20; 21]. Early experiments have identified the visual component as the dominant influence in the overall audio-visual quality; yet, it has been argued that this influence does not apply to all types of audio-visual applications. Studies have found the audio component as being very important in applications like video conference [20]. Other studies have confirmed that audio and video interaction depends on human, technological, and contextual factors [9]. In order to have a deeper understanding of this interaction, researchers have proposed new methods to subjectively assess audio-visual quality, more specifically, long-duration audio-visual stimuli [22; 23]. However, there is a limited number of experiments that aim to study the overall audio-visual quality in video sequences.