| JCTVC-B083 [T. Suzuki (Sony)] Study of MC interpolation filter for bi-prediction
A bi-pred/single-pred motion compensation filter switching was proposed in the JCTVC-A103 response of Call for Proposala. This contribution provided additional information about this subject. In this technique, motion compensation interpolation filters are designed for single prediction and bi-prediction. The motion compensation filter sets are switched if the macroblock prediction mode is single predictive or bi-predictive at the macroblock level. A two tap bi-linear low pass filter is applied when a macroblock is encoded as bi-predictive, and this reportedly removes high frequency component too much in some cases. The coding efficiency can reportedly be improved by enhancing middle frequency response for bi-prediction. This contribution provides simulation results for this tool. The average BD bit rate gain is reportedly about 1.0%, with the maximum gain being about 14.9%. This contribution also provided some complexity analysis.
Lower encoder complexity for this scheme than SIFO (switched interpolation filter with offset), because the encoder does not need to choose which filter to apply – always one particular filter for bi-prediction and one other particular filter for single prediction.
The proponent indicated that some sequences outside of the CfP test set provided better performance.
Note: This proposal has no effect on I or P pictures.
The quarter-pel positions were derived directly in this design – which may have some effect on the measured performance.
It was remarked that the SIFO technique is not properly supported in conjunction with IBDI.
It was noted that although the average gain is not so significant, the gain on a couple of sequences was substantial.
Further study was encouraged.
General usage (for P and bi-prediction) of fixed 6-tap separable interpolation filters, having higher preservation of high frequency than the usual AVC filters. Further claim that bi prediction averaging loses high spatial frequency – therefore further incease of mid frequency in this case
Quarter-pel positions are derived directly (no additional bilinear filter to derive them from half-pel positions).
Complexity of encoder is less than for SAIF, because the second pass of motion compensation after derivation of adaptive filter coefficients is not necessary.
Gain shown on average (compared to SAIF) is around 1% in BR reduction.
IBDI is off, which may have an influence on the performance of SAIF that is compared against.
Dostları ilə paylaş: | 
