r19126 - trunk/DOCS/tech/nut.txt

Author: michael
Date: Mon Jul 17 01:47:12 2006
New Revision: 19126

Modified:
   trunk/DOCS/tech/nut.txt

Log:
clarify H.264 global header format


Modified: trunk/DOCS/tech/nut.txt
============================================================
==================
--- trunk/DOCS/tech/nut.txt	(original)
+++ trunk/DOCS/tech/nut.txt	Mon Jul 17 01:47:12 2006
 -525,6
+525,8 
         for(i=0; i<number_of_headers; i++)
             header[i]
     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)
 
 frame_code
     the meaning of this byte is stored in the main header
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michael <subversionmplayerhq.hu> writes:

> Author: michael
> Date: Mon Jul 17 01:47:12 2006
> New Revision: 19126
>
> Modified:
>    trunk/DOCS/tech/nut.txt
>
> Log:
> clarify H.264 global header format
>
> Modified: trunk/DOCS/tech/nut.txt
>
============================================================
==================
> --- trunk/DOCS/tech/nut.txt	(original)
> +++ trunk/DOCS/tech/nut.txt	Mon Jul 17 01:47:12 2006
>  -525,6 +525,8 
>          for(i=0; i<number_of_headers; i++)
>              header[i]
>      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.

-- 
Måns Rullgård
mruinprovide.com
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Hi

On Mon, Jul 17, 2006 at 01:09:37AM +0100, Måns Rullgård
wrote:
> michael <subversionmplayerhq.hu> writes:
> 
> > Author: michael
> > Date: Mon Jul 17 01:47:12 2006
> > New Revision: 19126
> >
> > Modified:
> >    trunk/DOCS/tech/nut.txt
> >
> > Log:
> > clarify H.264 global header format
> >
> > Modified: trunk/DOCS/tech/nut.txt
> >
============================================================
==================
> > --- trunk/DOCS/tech/nut.txt	(original)
> > +++ trunk/DOCS/tech/nut.txt	Mon Jul 17 01:47:12
2006
> >  -525,6 +525,8 
> >          for(i=0; i<number_of_headers; i++)
> >              header[i]
> >      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 ...

[...]
-- 
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Michael Niedermayer <michaelnigmx.at> writes:

> Hi
>
> On Mon, Jul 17, 2006 at 01:09:37AM +0100, Måns Rullgård
wrote:
>> michael <subversionmplayerhq.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.

-- 
Måns Rullgård
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Måns Rullgård wrote:
> Michael Niedermayer <michaelnigmx.at> writes:
> 
>> Hi
>>
>> On Mon, Jul 17, 2006 at 01:09:37AM +0100, Måns
Rullgård wrote:
>>> michael <subversionmplayerhq.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.

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Baptiste Coudurier <baptiste.couduriersmartjog.com> writes:

> Måns Rullgård wrote:
>> Michael Niedermayer <michaelnigmx.at> writes:
>> 
>>> Hi
>>>
>>> On Mon, Jul 17, 2006 at 01:09:37AM +0100, Måns
Rullgård wrote:
>>>> michael <subversionmplayerhq.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.

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Hi

Måns Rullgård wrote:
>> [...]
>>
>> 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.
> 

Ah thanks. That is indeed simpler than putting the NAL size
;)

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