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Πλοήγηση Διδακτορικές διατριβές ανά Θέμα "Audio quality"

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  • Μικρογραφία εικόνας
    Τεκμήριο
    Quality of musicians' experience in network music performance
    (03/16/2022) Tsioutas, Konstantinos; Τσιούτας, Κωνσταντίνος; Athens University of Economics and Business, Department of Informatics; Polyzos, George C.; Siris, Vasilios A.; Apostolopoulos, Theodoros; Doumanis, Ioannis; Kalogeraki, Vana; Floros, Andreas; Xylomenos, George
    The increased use of tele-presence and tele-conferencing facilities, whether due to the need to isolate during a pandemic, or due to the desire to avoid costly and time consuming travel, prompted a renewed interest in Network Music Performance (NMP), where musicians collaborate remotely over the Internet in real time. Although the Internet has made dramatic leaps in capacity since the first NMP systems were created in the 20th century, the delays involved when communicating over the Internet, whether due to the physical distance between the endpoints, or due to the unpredictable nature of network traffic, are an important hindrance to the widespread use of NMP applications.The main question that this thesis attempts to answer is how much delay humans are able to tolerate for NMP to be acceptable. To achieve this goal, we first identify the factors influencing the Quality of Musicians' Experience (QoME) during NMP. Out of these factors, we single out audio delay, which makes or breaks a performance. We also consider audio quality, as it may be reduced to save bandwidth, without resorting to delay-inducing audio compression. A review of the literature shows that past work on evaluating the human tolerance to delay during NMP either employs a scenario where music is not performed, that is, synchronization of hand claps, or involves a very small number of experiments, thus having low statistical significance.Before embarking on a large scale study of NMP with actual musical performances, we first performed two exploratory studies. The first study tested our experimental setup, including the software and hardware employed, so as to ensure that the testing environment was acceptable to musicians and that we could gather accurate data without interruptions. The second study tested our assessment method, which consisted of questionnaires answered by each participant at the end of every performance, with a small number of musicians. Based on these studies, we then designed and carried out the largest NMP study to date with actual musicians performing real musical pieces. In this study, we varied either audio delay or audio quality in a systematic manner, gathering up answers to a fine-tuned questionnaire for QoME assessment. This subjective evaluation revealed that after crossing a quality threshold, further increasing audio quality had no discernible effects to QoME, indicating that when bandwidth is limited, we can sacrifice (up to a point) audio quality to reduce the required bitrate, without resorting to compression. On the other hand, we found that varying delay did have a statistically significant effect to QoME. More importantly though, our results indicate that the delay threshold up to which NMP is feasible is closer to 40~ms, rather than the 25-30~ms previously considered acceptable. Having recorded audio and video from all sessions, we complemented this subjective study with three additional evaluation methods, making our work the first multimodal study of the QoME for NMP. First, we performed tempo analysis on the recorded audio, to assess the highest delay at which the musicians could maintain a steady tempo; the results from this study confirmed that delays of up to 40~ms are acceptable for NMP, as indicated by the subjective study. Second, we analyzed the audio features of the recordings, finding that delay had a larger impact on percussive instruments and musicians performing rhythm parts; this result confirmed similar results from a previous, but much smaller study. Third, we analyzed the video recordings in order to detect the emotions felt by the musicians using machine learning methods, finding that as audio delay or audio quality was varied there were clear disruptions in the emotions of the musicians; while these results are intriguing, they were not clear enough to substitute the subjective analysis.