This paper describes a new flicker suppression method for periodically inserted Intra-coded Pictures (I-pictures) in H.264 video coding. An H.264 encoder periodically inserts I-pictures for channel hopping and random access. The coding noise pattern for I-pictures differs from that of previously appearing Predictive-coded Pictures (P-pictures) because, unlike with P-pictures, inter-frame prediction is not used with I-pictures. This discontinuity in coding noise patterns generates intra-flicker and heavily degrades subjective video quality at low bit rates. We propose Detented Quantization (DQ) to reduce the discontinuity in coding noise patterns between P-pictures and I-pictures. DQ stabilizes the representation levels of input coefficients in Ipictures on the basis of a derivation of those of the intercoded images produced from previous P-pictures. Simulation results show that DQ reduces intra-flicker by more than 50% in H.264 video coder JM8.6, and it significantly improves subjective video quality.
This paper presents a Reduced-Reference based video quality estimation method suitable for individual end-user quality monitoring of IPTV services. With the proposed method, activity values (spatial frequency levels) for individual given-size pixel blocks of an original video are transmitted to end-user terminals. At the end-user terminals, the video quality of a received video is estimated on the basis of the activity-difference between the original video and the received video. Psychovisual weighting with respect to the activity-difference is also applied to improve estimation accuracy. In addition, lowbit-rate transmission is achieved by using temporal subsampling and by transmitting only the lower six bits of each activity value. The proposed method achieves accurate video quality estimation using only low-bit-rate original video information (15kbps for SDTV). The correlation coefficient between actual subjective video quality and estimated quality is 0.901 with 15 kbps side information.
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