[ogg-dev] How Ogg mappings translate into the codecs parameter in Ogg media types

Silvia Pfeiffer silviapfeiffer1 at gmail.com
Thu Jun 5 22:52:02 PDT 2008

Further to this - I am staring at some of the other headers and
wondering how some of those fields came together.

I particularly see where the "packtype" is used, the number seems to
be intentionally different between the codes - apart from kate which
just copied the one from Theora. Also, it would be good if we can keep
our magic numbers to the first 8 bytes.

So, I am wondering: should we remove kate, mng, png, jng, yuv4mpeg
from the RFC since they have not officially been agreed on yet or

Instead of putting a "complete" list into the RFC (with some potential
bugs), I'd suggest to keep all of these specs in the wiki and work on
improving them there. The RFC should just contain the ones that are
widely approved and distributed.

Comments, anybody?


On Fri, Jun 6, 2008 at 2:08 PM, Silvia Pfeiffer
<silviapfeiffer1 at gmail.com> wrote:
> Hi all,
> I am trying to set up the codecs table in the wiki and we have played
> a bit with Dirac to find out what existing tools write into the
> header.
> The Schroedinger implementation by Fluendo uses (or used to use)
> "KW-DIRAC" as the identifier in the Ogg header.
> "BBCD" is the identifier of each of the Dirac data packages.
> More recently, I read that the Dirac Sequence header will be used as
> the Ogg BOS packet directly.
> I'm not sure this is the best solution and I'm not sure this is a
> final decision either.
> I believe it has to be sorted out properly and would suggest that
> until such time we take the Dirac "codecs" specification out of this
> Internet-Draft.
> Comments welcome!
> Cheers,
> Silvia.
> On Sat, May 31, 2008 at 2:20 AM, Ivo Emanuel Gonçalves
> <justivo at gmail.com> wrote:
>> I received the following comment regarding the table:
>>> The table contains a mix of octal and hexadecimal 'escape sequences'
>>> for non-printable / non-ASCII octets.
>>> I strongly suggest to only use a single kind of numerical escapes.
>> Is this feasible or even desired, or should we leave things as they are?
>> For reference, this is how the table looks right now:
>> Codec Identifier             | Codecs Parameter
>> -----------------------------------------------------------
>>  char[5]: 'BBCD\0'            | dirac
>>  char[5]: '\177FLAC'          | flac
>>  char[7]: '\x80theora'        | theora
>>  char[7]: '\x01vorbis'        | vorbis
>>  char[8]: 'Speex   '          | speex
>>  char[8]: 'OggMIDI\0'         | midi
>>  char[8]: 'CMML\0\0\0\0'      | cmml
>>  char[8]: '\211PNG\r\n\032\n' | png
>>  char[8]: '\212MNG\r\n\032\n' | mng
>>  char[8]: '\213JNG\r\n\032\n' | jng
>>  char[8]: 'CELT    '          | celt
>>  char[8]: 'PCM     '          | pcm
>>  char[9]: '\x80kate\0\0\0\0'  | kate
>>  char[9]: 'YUV4MPEG2'         | yuv4mpeg
>> (Don't expect it to look pretty without a monospaced font)
>> -Ivo
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