[Mp4-tech] [H264] delta_pic_order_cnt[0] parameter in POC type 1

[Rajiv Bajpai]

Dear Experts
  I have got one doubt regarding delta_pic_order_cnt[0] syntax element for POC mode 1 in slice header. 
  Is this parameter  always zero for IDR pic when poc type == 1;? This I could not find anywhere in the standard( or may be this can be implied)
  In the JM reference decoder, this parameter is forced to set to be zero irrespective of what is decoded from the stream.
  file: header.c, line no: 632
  {"
  img->delta_pic_order_cnt[0]=0; //ignore first delta
  "} 
  If there is no constraint on delta_pic_order_cnt[0] to be zero for IDR pic then above stated line of code creates problem.
  For example, if delta_pic_order_cnt[0] is non zero  for a picture and the picture has multiple slices then the above code causes detection of new picture for every different slices of the same picture. Since saving of the current slice fields are done in “exit_slice()” function which causes delta_pic_order_cnt[0] to be zero for old slice.
  So for the next slice of the same picture, 
  old_slice.delta_pic_order_cnt[0] != img->delta_pic_order_cnt[0] condition becomes true for POC mode 1 which falsely assign the next slice of the same picture to new picture;
  Any feedback and comment is highly appreciated
  Regards,
  Rajiv
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