1Mbps is enough: video quality and individual idiosyncrasies in multiparty HD video-conferencing

Most video platforms deliver HD video in high bitrate encoding. Modern video-conferencing systems are capable of handling HD streams, but using multiparty conferencing, average internet connections in the home are on their bandwidth limit. For properly managing the encoding bitrate in videoconferencing, we must know what is the minimum bitrate requirement to provide users an acceptable experience, and what is the bitrate level after which QoE saturates?. Most available subjective studies in this area used rather dated technologies. We report on a multiparty study on video quality with HD resolution. We tested different encoding bitrates (256kbs, 1024kbs and 4096kbs) and packet loss rates (0, 0.5%) in groups of 4 participants with a

The Influence of Audio and Video Quality on Perceptions of the Psychotherapist

The recent Coronavirus pandemic made remote means of conducting psychotherapy more common, and although there is a large amount of research on the mode of therapy, little research exists on the effects of video and audio quality on perceptions of the therapist. The purpose of this study was to investigate how the evaluation of a therapist changes when viewing different audiovisual qualities of recorded in-person therapy interactions. Participants were randomly assigned to view audio or video therapy interactions with differing levels of audiovisual quality. Analyses revealed a statistically significant difference in observer perceptions of interpersonal characteristics, such as empathy and alliance, when viewing different audiovisual qualities. Follow-up analyses indicated higher levels of the interpersonal perceptions when viewing therapy interactions of poor audiovisual quality, indicating that therapists were viewed as having more positive interpersonal characteristics when the audiovisual quality was distorted. These results suggest that concern about audio and video quality in online therapy interactions may be misplaced

The contrast effect: QoE of mixed video-qualities at the same time

In desktop multi-party video-conferencing videostreams of participants are delivered in different qualities, but we know little about how such composition of the screen affects the quality of experience. Do the different videostreams serve as indirect quality references and the perceived video quality is thus dependent on other streams in the same session? How is the relation between the perceived qualities of each stream and the perceived quality of the overall session? To answer these questions we conducted a crowdsourcing study, in which we gathered over 5000 perceived quality ratings of overall sessions and individual streams. Our results show a contrast effect: high quality streams are rated better when more low quality streams are co-present, and vice versa. In turn, the quality p

Subjective quality assessment of multichannel audio accompanied with video in representative broadcasting genres

Immersive broadcasting applications have received a lot of attention in the last years. In this context, the development of advanced HDTV and 3DTV formats is being successfully adopted by the consumer market, having a strong impact in the way that traditional broadcasting contents are displayed to final users. Together with the above advances in video technology, multichannel spatial audio has also experienced a considerable impulse within the audiovisual industry. However, the need for specific production tools and loudspeaker setups corresponding to multiple competing audio formats seems to be an important factor affecting their adoption by the consumer community. Moreover, it is well-known that the perceived audio quality is highly influenced by the reproduction context, where the existing multimodal interaction between audio and video plays a very important role. This paper presents a formal evaluation of the perceived sound quality provided by several spatial audio formats accompanied with video in the context of television broadcasting. Stereo, advanced surround formats and 3D Binaural sound are evaluated considering a set of representative broadcasting contents (sports, movies, music and animation) to assess their impact on the perceptual attributes contemplated within the international recommendations.The Spanish Ministry of Economy and Competitiveness and FEDER supported this work under the projects TEC2012-37945- 1091 C02- 01/02.Cobos Serrano, M.; López Monfort, JJ.; Navarro Ruiz, JM.; Ramos Peinado, G. (2015). Subjective quality assessment of multichannel audio accompanied with video in representative broadcasting genres. Multimedia Systems. 21(4):363-379. doi:10.1007/s00530-013-0340-2S363379214Apostolopoulos, J., Chou, P., Culbertson, B., Kalker, T., Trott, M., Wee, S.: The road to immersive communication. Proc. IEEE 100(4), 974–990 (2012). doi: 10.1109/JPROC.2011.2182069Huang, Y., Chen, J., Benesty, J.: Immersive audio schemes. IEEE Signal Process. Mag. 28(1), 20–32 (2011). doi: 10.1109/MSP.2010.938754Huynh-Thu, Q., Barkowsky, M., Le Callet, P.: The importance of visual attention in improving the 3D-TV viewing experience: overview and new perspectives. IEEE Trans. Broadcast. 57(2), 421–431 (2011). doi: 10.1109/TBC.2011.2128250Wang, K., Barkowsky, M., Brunnstrom, K., Sjostrom, M., Cousseau, R., Le Callet, P.: Perceived 3D TV transmission quality assessment: multi-laboratory results using absolute category rating on quality of experience scale. IEEE Trans. Broadcast. PP(99), 1 (2012). doi: 10.1109/TBC.2012.2191031Zhang, L., Vazquez, C., Knorr, S.: 3D-TV content creation: automatic 2D-to-3D video conversion. IEEE Trans. Broadcast. 57(2), 372–383 (2011). doi: 10.1109/TBC.2011.2122930Kyriakakis, C., Tsakalides, P., Holman, T.: Surrounded by sound. IEEE Signal Process. 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MIDI. Una guida al protocollo, alle estensioni e alla programmazione

illustratorIl testo mira ad affrontare l’intero ecosistema MIDI dal punto di vista dei protocolli, formati, dispositivi hardware e software e librerie di supporto alla programmazione. Il volume si articola in due parti, la prima delle quali è dedicata alla descrizione del protocollo originario e delle sue estensioni, fino alla recentissima introduzione del MIDI 2.0 (febbraio 2020). La seconda parte affronta il tema della programmazione di applicativi software secondo diverse filosofie, che spaziano dall’uso di linguaggi multi-piattaforma “tradizionali” (Java) all’adozione della Web MIDI API per la programmazione web