[vorbis] xml stream formats

[John Morton]

On Thu, 6 Jul 2000 11:53:12 -0700 (PDT) you wrote:

 > On Thu, 6 Jul 2000, Bob Miller wrote:
 > 
 > > I'm not sure I understand how this streaming XML stuff is going
 > > to be used.  I'm envisioning something like this.
  
[snip]
 
 > Consider a live streaming context, when you have people connecting "in the
 > middle" of a song. 

Ok, lets. If you come in at the middle of a song (or movie, or whatever),
then you've either missed the metadata packet, or it's being repeatable
throughout the transmission (blech!) and you'll get a parsible packet
soon, or it's available on a seconary channel
(http://streaming.site/what's.playing.now.xml or whatever). I don't see a
problem so far.

You want to integrate the lyrics with time signitures with the stream? No
problem:

<?xml version="1.0"?>
<!DOCTYPE vorbis-metadata SYSTEM "http://www.xiph.org/vorbis-lyrics.dtd">
<vorbis::metadata>
  <timestamp t="00:01.38"/> 
  <chord symbol="Am" fingering="http://www.xiph.org/guitarcharts/Am.png"/>
  <lyric>Pic</lyric>
 </vorbis::metadata>

Shove each of these little XML lyric/subtitle/whatever packets in where
you need them. Notice how small they are? Think of how tiny they'll be
once you compress them with zlib (we're going to do this, right?).

Basically, the metadata doesn't need to stream, because it's already small
enough to be considered a packet, compared to the size of the multimedia
file that it's being sent with. If you can stream a 64kb/s audio
transmission, then you can download 8k of compressed metadata in a second.
An 8k compressed packet would uncompress to 16k of XML marked up text
(probably more), which is plenty of room to store:

 - The title and artist
 - A comprehensive list of all the personel involved in it's production
 - Lyrics, chords, guitar tabs, etc
 - A bunch of particulars useful for advising mixing and beatmatching.
 - Entries describing the relationship between secondary multimedia in the
    stream and the main thing being streamed ('That thing is the album
    cover')
 - A detailed discussion about the work by the artist.

Realistically the metadata will be smaller, and the time dependent stuff
can be scattered throughout the stream. Video will tend to have more
metadata, but it tends to require more bandwidth, too. 

Of course maybe I'm wrong and there is some low bitrate/high metadata
application that requries the metadata to be broken down into units
smaller than one XML doc, even compressed, can readily be, but I've got no
idea what it is.

John

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.