[NUT-devel] Re: r19126 - trunk/DOCS/tech/nut.txt

[Måns Rullgård]

Baptiste Coudurier <baptiste.coudurier at smartjog.com> writes:

> Måns Rullgård wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> 
>>> Hi
>>>
>>> On Mon, Jul 17, 2006 at 01:09:37AM +0100, Måns Rullgård wrote:
>>>> michael <subversion at mplayerhq.hu> writes:
>>>>
>>>>>      Note, this is the same format these codecs use in matroska
>>>>> +    for H.264 the NAL units MUST be formated as in a bytestream 
>>>>> +    (with 00 00 01 prefixes)
>>>> It's actually 00 00 00 01 (four bytes) for the NAL units that we're
>>>> dealing with here.  To make this unambiguous, I would change the text
>>>> to read
>>>>
>>>>   For H.264 the format MUST be that specified in ITU-T Rec. H.264
>>>>   Annex B Byte stream format.
>>> agree, but we should still mention that its 0 0 0 1 + NAL as not
>>> every reader of nut.txt will have (or want) every spec of every
>>> codec ...
>> 
>> Fine by me.  I just want the proper reference included for those that
>> do have the document.
>> 
>
> Actually, some NALs (PPS, SPS ?) can start with 00 00 01 IIRC.

Actually, it's the opposite.  Quote from the spec:

  When any of the following conditions are fulfilled, the zero_byte
  syntax element shall be present.

  - the nal_unit_type within the nal_unit( ) is equal to 7 (sequence
    parameter set) or 8 (picture parameter set)
  - the byte stream NAL unit syntax structure contains the first NAL
    unit of an access unit in decoding order, as specified by subclause
    7.4.1.2.3.

-- 
Måns Rullgård
mru at inprovide.com