Keiichi Chono

Detented Quantization to Suppress Flicker Artifacts in Periodically Inserted Intra-Coded Pictures in H.264 Video Coding

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 I-pictures on the basis of a derivation of those of the inter-coded 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.

In-loop noise shaping based on pseudo noise injection and Wiener filtering

This paper proposes an in-loop noise shaping method based on the combination of pseudo noise injection and Wiener filtering for High Efficiency Video Coding (HEVC). In deblocking process, the proposed method injects pseudo noise into the vicinities of deblocked edges where signal-dependent coding noises are supposed to appear. The pseudo noise injection introduces a masking effect of signal-dependent noise with signal-independent noise. Since subsequently applied Wiener filtering accomplishes optimal noise reduction in a minimum-mean-squared-errors sense, it minimizes the deleterious impact of the pseudo noise injection on coding performance. Simulation results using HEVC Test Model software show that the proposed method successfully suppresses banding artifacts with a negligible impact on PSNR values, bit rates, and encoder/decoder runtime measures.

Enhanced reconstruction of AVC/H.264 intra video based on motion compensated temporal filtering and total-variation regularization

This paper proposes an enhanced reconstruction method of AVC/H.264 intra video based on Motion Compensated Temporal Filtering (MCTF) and Total-Variation (TV) regularization. The MCTF attenuates temporal fluctuations in block transform coefficient values of individual decoded video frames on the basis of Motion Estimation (ME). However, the attenuated block transform coefficients lead to spatial discontinuities on the associated image area. The TV regularization technique reduces the spatial discontinuities, and also suppresses quantization noises of the image edge vicinities that are supposed to belong to a smooth object while keeping the image edge sharpness. The proposed reconstruction method thus enhances the quality of decoded video frames degraded by flicker artifacts and ringing noises. Simulation results show that the proposed method improves the subjective video quality of AVC/H.264 intra video, and the attainable bit rate up to 16.1% at the same objective video quality.

Efficient binary representation of delta Quantization Parameter for High Efficiency Video Coding

This paper proposes an efficient binary representation of delta Quantization Parameter (QP) for High Efficiency Video Coding (HEVC). Video encoders adapt QPs of coding blocks for visual quality optimization and rate control. Although they send only delta QPs (dQPs) obtained by causal prediction, the side information overhead is expensive. Therefore the HEVC design necessitates an efficient dQP coding. The proposed scheme converts a dQP to a binary string in which the first and second bins indicate the significance and sign of the dQP respectively and the rest represents the magnitude minus 1. Furthermore, it detects and truncates redundant bins in the binary strings by using the sign and an admissible dQP range. Thus it reduces the length of dQP binary strings and improves dQP coding efficiency. Simulation results using HEVC reference software demonstrate that the proposed scheme improves the dQP coding efficiency by 6% while reducing its bin rates by 25%.