The Joint Collaborative Team on Video Coding (jct-vc) of itu-t wp3/16 and iso/iec jtc 1/ sc 29/ wg 11 held its tenth meeting during 11-20 July 2012 at the City Conference Centre (ccc), a k. a

5.19.2I_PCM (4 – done)

For I_PCM related proposals, the schemes are categorized as follows:

• 
  I_PCM signalling
  
  • 
    Burst IPCM (JCTVC-J0153 – also proposed at previous meeting)
    
  • 
    Conditional signalling of pcm_flag (JCTVC-J0277)
    
• 
  Harmonization of filtering control of I_PCM and lossless coding modes
  
  • 
    Syntax harmonization of the I_PCM and TransQuantBypass modes (JCTVC-J0168)
    
  • 
    Semantics harmonization of loop filtering control for I_PCM and TransQuantBypass modes (JCTVC-J0169)
    

No action was taken in this area.
JCTVC-J0153 Burst I_PCM Signalling [M. Coban, W.-J. Chien, J. Chon, M. Karczewicz (Qualcomm)]

BoG suggested to defer discussion of this until reaching a decision on bit usage per region.

The current scheme sends the number of I_PCM blocks first, then byte aligns, and then sends the data, then goes back to CABAC operation.

The proposed scheme sends an I_PCM block, then a flag indication whether another one follows, then another one, etc., and byte aligns, then goes back to CABAC operation.

Pros & Cons:

• 
  In the current scheme, the I_PCM blocks are byte aligned and packed together in a decoding-friendly manner. If the encoder finds it difficult to send blocks in burst mode, it would always signal one block only (which, together with the byte alignment padding, would cost 8 bits per CU, plus CABAC termination bits per CU, and repeatedly stops and restarts CABAC).
  
• 
  In the proposed scheme, the encoder can decide one-by-one how many it will send, without look-ahead.
  

It was noted that emulation prevention bytes can interact with the efficiency when strings of zero-valued samples appear in the source data.

Several non-proponents indicated that the current scheme is preferable, stating that the encoder would often know how many CUs it wants to send and that having byte alignment of the PCM data is desirable. No action taken on this.

JCTVC-J0411 Crosscheck of Burst IPCM Coding Signalling (JCTVC-J0153) [G. Clare, F. Henry (Orange Labs)] [late]
JCTVC-J0277 Interaction between pcm_flag and cu_transquant_bypass_flag [R. Joshi, G. Van Der Auwera, M. Karczewicz (Qualcomm)]
JCTVC-J0168 AHG11: Syntax harmonisation of the I_PCM and TransQuantBypass modes [E. François, P. Onno, G. Laroche, T. Poirier, M.Shima (Canon)]
JCTVC-J0426 Crosscheck of Syntax harmonisation of the I_PCM and TransQuantBypass modes (JCTVC-J0168) [G. Clare, F. Henry (Orange Labs)] [late]
JCTVC-J0169 AHG11: Loop filtering control for I_PCM and TransQuantBypass modes [E. François, P. Onno, G. Laroche, T. Poirier, M.Shima (Canon)]