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.