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

4.3SCE3: Inter-layer filtering (5)

4.3.1SCE3 summary and general discussion

Initially reviewed Wed 23rd. evening (JRO).

JCTVC-O0033 SCE3: Summary report of SHVC Core Experiment on Inter-layer Filtering [J. Chen, E. Alshina, J. Dong, M. Sychev]

4.3.2SCE3 primary contributions

JCTVC-O0078 SCE3: performance and complexity test for cross-color inter-layer filter [X. Li, J. Chen, M. Karczewicz (Qualcomm), E. Alshina, A. Alshin(Samsung), J. Dong, Y. Ye, Y. He (InterDigital)]

Additional processing step applied after upsampling of chroma components: The chroma components of inter layer reference picture are enhanced by adding an offset which is derived by applying a high pass filter on the base layer luma component. 8-tap non-separable filter, adapted region wise, up to 16 rectangular regions

Parameters signaled at slice header (currently only would allow 1 slice per picture); different way of signalling (a lower-level adaptation parameter set) would be necessary.

Relation with tile/wavefront processing? Implication on multi-core implementation? Conflict might apply in case of on-the-fly upsampling

Question: Impact on coding? Low latency possible? In current implementation, picture wise processing is applied.

Has it been checked for visual artifacts? Not systematically, but it is reported that some visual inspections did not unveil problems such as boundary artifacts.

Gains:

• 
  Spatial scalability average: −0.8% (Y) / −11.7% (U) / −21.7% (V)
  
• 
  SNR scalability average: −0.5% (Y) / −10.7% (U) / −19.8% (V)
  

Initial assessment: 4 multiplications per enhancement layer luma sample, moderate additional memory.

Opinion of some experts: The method gives a reasonable gain versus complexity tradeoff for the case of spatial scalability. Other experts do not agree with this assessment.

M. Zhou and Mediatek to further investigate complexity impact for hardware implementation, and discuss offline with proponents.

More proper way of signaling should be investigated and further discussed.

(Further reviewed Sat 26th afternoon JRO)

M. Zhou reported back on investigation, for decoder

• 
  increase of HW complexity of upsampler 25-30%
  
• 
  no additional line buffer
  

for encoder:

• 
  access the chroma samples once for computing parameters, once for interpolation processing
  
• 
  extra functional blocks
  

Non-negligible impact on encoder and decoder complexity

Request made by last meeting about potential visual artifacts not satisfied

Request made by last meeting about studying one-pass encoder not satisfied

Too many reservations by other experts - no action