Abstract
This paper presents an audiovisual quality model for IPTV services. The model estimates the audiovisual quality of standard and high definition video as perceived by the user. The model is developed for applications such as network planning and packet-layer quality monitoring. It mainly covers audio and video compression artifacts and impairments due to packet loss. The quality tests conducted for model development demonstrate a mutual influence of the perceived audio and video quality, and the predominance of the video quality for the overall audiovisual quality. The balance between audio quality and video quality, however, depends on the content, the video format, and the audio degradation type. The proposed model is based on impairment factors which quantify the quality-impact of the different degradations. The impairment factors are computed from parameters extracted from the bitstream or packet headers. For high definition video, the model predictions show a correlation with unknown subjective ratings of 95%. For comparison, we have developed a more classical audiovisual quality model which is based on the audio and video qualities and their interaction. Both quality- and impairment-factor-based models are further refined by taking the content-type into account. At last, the different model variants are compared with modeling approaches described in the literature.
Highlights
In order to achieve a high degree of user satisfaction for current and upcoming video services like video on demand (VoD), internet protocol television (IPTV), and mobile television (MoTV), perceived quality needs to be estimated both in the network planning phase and as part of the service monitoring
For each of the five subjective tests, the scores were averaged over subjects, yielding mean opinion scores (MOS), were linearly transformed to the 5-point absolute category rating (ACR) MOS scale by aligning the numbers of the scales, and further transformed to the 100-point model scale using the conversion defined in ITU-T Recommendation G.107 [14]
This choice is motivated by two reasons: (a) the audiovisual quality model is to be applied on audiovisual sequences with various contents, and a predicted quality value per sequence is required; we want to capture the quality variation due to content; (b) the audiovisual quality model developed for all contents, that is, with one set of coefficients valid for all contents, is to be compared to an audiovisual quality model with different sets of coefficients for each content
Summary
In order to achieve a high degree of user satisfaction for current and upcoming video services like video on demand (VoD), internet protocol television (IPTV), and mobile television (MoTV), perceived quality needs to be estimated both in the network planning phase and as part of the service monitoring. EURASIP Journal on Image and Video Processing versions do not yet cover the effect of transmission errors This latter point is problematic since, in the case of the timevarying degradation due to transmission errors, the impact of audio and video quality on the overall audiovisual quality as well as their interaction might differ from the case of compression artifacts. Based on the quality perception tests conducted during model development, we have analyzed the influence of the degradation type and of the audiovisual content on the quality impact of audio and video. The concept of impairment factors is based on the findings by Allnatt for broadcast TV [13], yielding the assumption that certain kinds of impairment factors may be considered as additive on an appropriate (perceptual) quality rating scale This impairment factor principle has been adopted by the so-called E-model, a parameter-based network planning quality model standardized by the ITUT [14] for speech services. Speech Speech on noise Classical music Pop music with singer extends the work presented in [18] by providing a deeper insight on the comparison of the models’ performance, by addressing the SD resolution in addition to the HD one, by sharpening the analysis of the degradation-type impact on audiovisual quality, and by analyzing the quality impact of the audiovisual content type
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