Parametric bitstream-based quality assessment of progressive download and adaptive audiovisual streaming services over reliable transport -Quality integration module (Study Group 12)
This Recommendation1 describes an objective parametric quality assessment model as part of the ITU-T P.1203 series of ITU-T Recommendations. The model specified herein predicts the impact of audiovisual quality variations and stalling events on quality experienced by the end user in multimedia mobile streaming and fixed network applications using adaptive bitrate streaming@ based on a previous estimation of audio and video quality and information on stalling events during the media session. The model predicts mean opinion scores (MOS) on a 5-point ACR scale (see [ITU-T P.910]) as a final audiovisual quality MOS score (as defined in [ITU-T P.911]@ for instance). The model also outputs a perceptual stalling quality indicator@ a final audiovisual compression quality score and a list of integrated audiovisual quality scores for diagnostic purposes. This model cannot provide a comprehensive evaluation of transmission quality as perceived by a particular end user because its scores reflect the impairments on the IP network being measured@ which may only be part of the end-to-end connection. Furthermore@ the scores predicted by a parametric model necessarily reflect an average perceptual impairment. Note also that the model is developed with a specific encoder and decoder pair. If a different encoder and decoder pair is used in a monitoring situation the scores will not reflect that. Note that user interactions (such as pausing@ seeking@ user initiated quality change@ user initiated play or user initiated end) are NOT considered in this model either. The effects of audio level@ noise@ delay (and corresponding similar video factors) and other impairments related to the payload are not reflected in the scores computed by this model. Therefore@ it is possible to have high scores with this model@ yet have a poor quality stream overall. Moreover@ the scores predicted by a parametric model (i.e.@ without access to payload information) necessarily reflect a somewhat simplified representation of the perceptual impairment of the considered stream. 1 This Recommendation includes an electronic attachment containing the full 20 trees described in clause 8.4.