Opened 9 years ago

Closed 9 years ago

#1043 closed defect (fixed)

Confusion about decoding engine initialization after pcm_flag

Reported by: peterderivaz Owned by:
Priority: minor Milestone:
Component: Text Version: D10 (L1003) v31
Keywords: Cc: bbross, wjhan, jct-vc@…

Description

9.3 "CABAC parsing process for slice segment data" says that the decoding engine is initialized after reading pcm_flag and decoding a 1.

This implies that a decoder should:

  1. Read pcm_flag
  2. Read 9 bits giving the start for ivlOffset
  3. Discard alignment bits
  4. Read PCM samples

However, I suspect the intention is to have the decoding engine initialized only after reading the PCM samples:

  1. Read pcm_flag
  2. Discard alignment bits
  3. Read PCM samples
  4. Read 9 bits giving the start for ivlOffset


(The reference decoder uses the second method in function TDecSbac::parseIPCMInfo)

Change History (5)

comment:1 Changed 9 years ago by DefaultCC Plugin

  • Cc bbross wjhan jct-vc@… added

comment:2 Changed 9 years ago by bbross

In AVC, the corresponding part is described as follows:

"In case the request for a value of a syntax element is processed for the syntax element mb_type and the decoded value of mb_type is equal to I_PCM, the decoding engine is initialised after the decoding of any pcm_alignment_zero_bit and all pcm_sample_luma and pcm_sample_chroma data as specified in clause 9.3.1.2."

Thus changing the aforementioned HEVC text to

"In case the request for a value of a syntax element is processed for the syntax element pcm_flag and the decoded value of pcm_flag is equal to 1, the decoding engine is initialized after the decoding of any pcm_alignment_zero_bit and all pcm_sample_luma and pcm_sample_chroma data as specified in subclause 9.3.2.5."

would fix that.

comment:3 Changed 9 years ago by kchono

I think that the suggested HEVC text fix is correct. Thank you very much!

comment:4 Changed 9 years ago by bbross

  • Milestone HM-10.1 deleted
  • Version changed from D10 (L1003) v28 to D10 (L1003) v31

comment:5 Changed 9 years ago by bbross

  • Resolution set to fixed
  • Status changed from new to closed

Fixed in v32.

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  • Keiichi Chono(Participant)
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