[Mp4-tech] Dropping NAL units on bit errors: Best approach?

[Samuel Rivas]

John Cox wrote:
> It is always legal to pack the end of a nal_unit with extra zeros
> (trailing_zero_8bits) so a non-start-of-AU NALU may appear to have three
> leading seros but in fact that is one zero on the end of the previous
> unit and two leading zeros on this unit.  This detail is important if
> you are trying to determine the exact byte on which a unit starts (e.g.
> when encapsulated in PES the PTS applies to the first unit which starts
> in that PES packet).

  I do not think it is that way. The spec reads:
"When any of the following conditions are fulfilled, the zero_byte
syntax element shall be present"
  I might have overlooked it, but I think there is not a statement
saying that "the zero_byte shall not be present otherwise". Thus,
following the description in B.1.1, any 0x00000001 is always a zero_byte
followed by a start_code_prefix_one_3bytes.
  Regards.
-- 
	Samuel