[vorbis-dev] Header

[Adam Whitehead]

Hi,

> Docs are incomplete; rather, the docs for the Ogg bitstream structure are
> there, but not yet the Vorbis stream type.  It's not complicated, just not
> written.

If you could provide me with brief details on the location/encoding of
the info within the files, I can get started writing the PHP script I need for
this to add OGG support to AudioPhilez.

> However, the Vorbisfile lib gives you all the functionality you mentioned 
> right now.  I'll give more details tomorrow (I'm just about to head off to 
> sleep).
> 

Is the source for this easy enough to understand? I'm hardly
an accomplished C/C++ programmer but if it is straightforward enough
and commented, I should be able to get something happening in PHP.

Regards,
Adam Whitehead
Netherworld Media
E-mail: adam at nwmedia.com.au
Phone: +61 (889) 279 898
FAX: +61 (889) 273 889
AudioPhilez (http://www.audiophilez.com)

----- Original Message ----- 
From: "Monty" <xiphmont at xiph.org>
To: <vorbis-dev at xiph.org>
Sent: Thursday, May 11, 2000 7:47 PM
Subject: Re: [vorbis-dev] Header 

> > 1. Will a standard MP3 decoder find 'sync' in an .OGG file?
> 
> No.  There is no commonality between the Ogg bitstream format and mp3.  Any
> byte matches would be purely accidental (and probably impossible, as Ogg does
> have 'magic' bytes to lead off).
> 
> > 2. Is there a simple header with bitrate information etc.
> > encoded in
> > the header? 
> 
> Yes.  Vorbis has three header packets; an initial small header uniquely 
> identifying Vorbis (as opposed to some other Ogg type) and a few basic 
> settings alone in the first Ogg bistream page.  The second and third packets 
> contain text comments (eg, artist, title) and the full bitstream setup 
> respectively.
> 
> > If someone could let me know of a doc with info
> > on
> > the header, I'd really appreciate it. I need info like
> > bitrate, sample rate,
> > embedded song name, artist name (if there is one, I sure
> > hope so!)
> > and I'll probably include all information that OGG stores
> > about the
> > file in my database.
> 
> Docs are incomplete; rather, the docs for the Ogg bitstream structure are
> there, but not yet the Vorbis stream type.  It's not complicated, just not
> written.
> 
> However, the Vorbisfile lib gives you all the functionality you mentioned 
> right now.  I'll give more details tomorrow (I'm just about to head off to 
> sleep).
> 
> > 3. I heard OGG supports variable bitrate. Is there an easy
> > way to calculate
> > the average bitrate? For MP3 files, I calculate average
> > bitrate on my site
> > by dividing file size by playtime etc.
> 
> That's a perfectly good way to do it.  Vorbisfile will also give you average 
> bitrate, as well as maximum and minimum rates (if they're set/bounded; that's 
> optional).
> 
> Monty
> 
> 
> --- >8 ----
> List archives:  http://www.xiph.org/archives/
> Ogg project homepage: http://www.xiph.org/ogg/
> 

--- >8 ----
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