Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

JCTVC-M0356 Cross-check for JCTVC-M0322 signalling of phase offset in up-sampling process [J. Dong, Y. Ye (InterDigital)] [late] [miss]
JCTVC-M0425 About phase calculation and up-sampling filter coefficients in JCTVC-M0188 and JCTVC-M0322 [E. Alshina, A. Alshin (Samsung)] [late]

TBA.

This report presents spectral characteristics analysis for new up-sampling filters proposed by InterDigital and Qualcomm for fractional positions not specified in SHVC Test Model 1/ SHVC Working Draft 1. A phase calculation bug in SHVC Test Model 1/ SHVC Working Draft 1 is reported and possible fixes are discussed.

The contribution asserts that the coefficients proposed in M0465 are considered to be well-designed based upon frequency analysis and consistent with current MC interpolation and upsampling filter, except for 3 phases, and alternatives are proposed. No experimental results are proposed.
JCTVC-M0465 Signaling of Phase Offset in Up-sampling Process and Chroma Sampling Location [L. Guo, J. Chen, M. Karczewicz (Qualcomm), J. Dong, Y. Ye, Y. He (InterDigital), K. Ugur, J. Lainema (Nokia)]

In spatial scalability coding, reference layer pictures are down-sampled versions of current layer pictures. The down-sampling locations are not normative part in the standard and can have different phase shifts. To avoid the mismatch between the down-sampling phase and the up-sampling phase, this contribution proposes to have indication of phase shift for the up-sampling process. In addition, this contribution proposes to signal chroma sampling locations and define the up-sampling filters for all 16 phases.

Combines aspects of M0188, M0231, and M0322

Proposes sampling_grid_information syntax structure, called from SPS extension, which begins with a presence flag. Applies only to SHVC and not MV-HEVC, so could consider applying conditions to send for SHVC but not MV-HEVC.

There was a qQuestion about what would happen if the base layer is interlaced. The c Contribution as drafted is aimed at progressive, not interlaced, video content.

Normative change to upsampling process, both for phase calculation and filtering coefficients, as need to fill in all 16 positions.

The usefulness of the chroma phase information was questioned.

The decoding process proposed in this contribution could also be used for arbitrary resizing.

Related to AHG13. The filter coefficients are related to SCE4.

The usefulness of the luma phase information was also questioned, the application need was questioned, as an encoder can control the downsampling, or pre-process to map the sampling grid. Some participants considered mentioned applications which could make use of this tool, and pre-processing would involve considerable encoder complexity.

Some experimental results were provided showing.

This solution vs adaptive filter is questioned. Adaptive filter coefficient generation has to guarantee avoiding overflow.

The fractional accuracy required is unclear – could lower than 1/16 sample provide similar performance?

Items to study in a CE coordinated by E. Alsina:

• 
  fractional pel accuracy
  
• 
  filter coefficients
  
• 
  source content with different characteristics. Could consider using sequences generated for early drafts of CfP which had different phase offsets, which are available.
  
• 
  fixed vs adaptive