ABSTRACT

1. ACCEPTANCE OF AUDIOVISUAL QUALITY IN ERRONEOUS TELEVISION SEQUENCES OVER A DVB-H CHANNEL H.264/AVC Encoder AAC Encoder H.264/AVC Encoder AAC Encoder H.264/AVC Encoder AAC Encoder H.264/AVC Encoder AAC Encoder Stream Mux Stream Mux Stream Mux Stream Mux Service Mux Gilbert Elliot Simulator DVB-H Channel Service De-Mux Stream De-Mux Stream De-Mux Stream De-Mux Stream De-Mux 3GPP Converter AAC Decoder 3GPP Converter AAC Decoder 3GPP Converter AAC Decoder 3GPP Converter AAC Decoder S. Jumisko-Pyykkö (a), Vinod Kumar M.V. (a), M. Liinasuo (b), M. M. Hannuksela (b) (a){@tut.fi, Tampere University of Technology}; (b){@nokia.com, Nokia Research Center} ABSTRACT In Digital Video Broadcasting for Handhelds (DVB-H), an audiovisual service is transmitted in time-slicing bursts to achieve power savings in receiving terminals. As in many other transmission schemes, the received data streams over DVB-H may contain residual transmission errors. The burst characteristics and appearance frequency of these transmission errors have an effect on the perceived audiovisual quality. The perceived quality is a significant factor in the end-user’s acceptance and the adoption of new mass products such as mobile television. This study investigated effects of four residual time-slice error rates on the overall subjective audiovisual quality. The quality was measured with subjective retrospective ratings of acceptance. Error rates of 1.7%, 6.9%, 13.8% and 20.7% were tested with clips from four popular television programs and evaluated by 30 participants. The results show that among the error rates simulated, error rates of 1.7% and 6.9% were experienced as acceptable, while error rates of 13.8% and 20.7% were perceived to be unacceptable. GOAL To study effects of residual time-slice error rates on the acceptance of overall subjective audiovisual quality Error pattern details: • RESEARCH METHOD • Participants: 30 • Aged18-45 years, equally stratified by age, gender, <20% professionals, normal/ corrected-to-normal visual acuity, colour vision and normal hearing • Test procedure: Retrospective ratings of acceptance • Pre-test: Sensory tests, demographic survey • Test: Anchoring & training, test with continuous assessment and retrospective ratings • Post-test: Content survey, interview • Contents: • - Potential for mobile TV, popular • Variations in the levels of spatial details, temporal motion and audiovisual characteristics • The length of the clips: 60s • Presentation of test material • Laboratory environment: ITU-T P.920 • Device: Nokia 6630 with headphones • Viewing distance: 44 cm • Audio loudness level: 75 dBA • 3 repetitions played in random order Simulation parameters: RESULTS Acceptance of different error rates (McNemar test): Acceptable: Error rates 1.7% and 13.8% Unacceptable: Error rates 13.8% and 20.7% Simulation setup: • DISCUSSION AND CONCLUSIONS • Acceptance threshold lies between time-slice error rates of 6.9% and 13.8% • Acceptance is affected by number of errors and error characteristics (duration, modalities)