Opened 8 years ago

Closed 8 years ago

#1018 closed defect (invalid)

Specification sometimes produces an extra alignment byte when using tiles

Reported by: peterderivaz Owned by: bbross
Priority: minor Milestone:
Component: Text Version: D10 (L1003) v23
Keywords: Cc: bbross, wjhan, jct-vc@…

Description

In 7.3.8.1 General slice segment data syntax of JCTVC-L1003_v24 the syntax calls byte_alignment when a new tile is detected.

The syntax for byte_alignment emits a 1 followed by zeros until the stream is aligned.

However, the decoder implementation in function TComInputBitstream::readOutTrailingBits of TComBitStream.cpp contains the code:

Void TComInputBitstream::readOutTrailingBits ()
{

UInt uiBits = 0;
while ( ( getNumBitsLeft() > 0 ) && (getNumBitsUntilByteAligned()!=0) )
{

read ( 1, uiBits );

}

}

which will not emit a 1 if the stream is already aligned.
This code is called from TDecSbac::updateContextTables when the CABAC engine needs to be reinitialized.

Which is the correct behaviour? (Or have I misunderstood something?)

Change History (4)

comment:1 Changed 8 years ago by DefaultCC Plugin

  • Cc bbross wjhan jct-vc@… added

comment:2 Changed 8 years ago by PhuongNguyen

This issue was also reported in the ticket #1011 :

http://hevc.kw.bbc.co.uk/trac/ticket/1011

There is also an ongoing discussion on how to interpret the bit equal to one when we decode a termination bin (pcm_flag, end_of_slice_segment_flag and end_of_sub_stream_one_bit) equal to one :

http://hevc.kw.bbc.co.uk/trac/ticket/980

I believe that we need to clarify the text as clear as possible on this issue to avoid difference in spec comprehension and mismatch in encoder behavior.

comment:3 Changed 8 years ago by peterderivaz

Thank you very much PhuongNguyen, I agree that this issue is already covered by the previous tickets and that this ticket can be closed as a duplicate.

Apologies for wasting your time.

comment:4 Changed 8 years ago by bbross

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