Vorbis dev - May 2004 - embedding a lot of vorbis comments

Dear list,

i want to embed some meta data in an ogg stream, which contains 
additional commands for the ogg player like setting the volume, panning 
etc. I.e. for fading out a song i would send several commands like "set 
volume to 99%", "set volume to 98%", "set volume to
97%" etc etc.

I thought using vorbis comments could be a good idea. But they would be 
spread over the whole file. Is this possible with vorbis comments? it 
seems that i can only send them when calling vorbis_analysis_headerout()...

Thanks,
Chris
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On Tuesday 11 May 2004 10:20, Christoph Rupp wrote:
> Dear list,
> 
> i want to embed some meta data in an ogg stream, which contains 
> additional commands for the ogg player like setting the volume, panning 
> etc. I.e. for fading out a song i would send several commands like
"set
> volume to 99%", "set volume to 98%", "set volume to
97%" etc etc.
> 
> I thought using vorbis comments could be a good idea. But they would be 
> spread over the whole file. Is this possible with vorbis comments? it 
> seems that i can only send them when calling vorbis_analysis_headerout()...
The first thing that comes to mind is what the spec has to say about comments:

  The Vorbis text comment header is the second (of three) header packets that 
  begin a Vorbis bitstream. It is meant for short, text comments, not 
  arbitrary metadata; arbitrary metadata belongs in a separate logical 
  bitstream (usually an XML stream type) that provides greater structure and 
  machine parseability. 

  The comment field is meant to be used much like someone jotting a quick note 
  on the bottom of a CDR. It should be a little information to remember the 
  disc by and explain it to others; a short, to-the-point text note that need 
  not only be a couple words, but isn't going to be more than a short 
  paragraph. The essentials, in other words, whatever they turn out to be, 
  [...]

http://www.xiph.org/ogg/vorbis/doc/v-comment.html

It would seem that what you're trying to do is something of an abuse of 
comments; my understanding is that tthey should all map to something that's 
meaningful to a human reader.

- -Scott

- -- 
New Orleans food is as delicious as the less criminal forms of sin.
 --Mark Twain
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Hi:

In addition to what others have written, the vorbis comment packet is in
the vorbis header.  Doing it the way you suggest means that you'd have to
start a new logical stream every time you wanted to change the volume,
which would waste a lot of space with duplicated codebooks and other header
stuff.

If you had to use comments, you might want to write comments with a time
specification as well as volume setting, all of which would be placed at
the start of the clip.  The player could then read these and act on them at
the appropriate time.  But like Jack said, this is a hack and using
something like MIDI to do this is by far the preferred way to do this.

Geoff.

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