[Vorbis] Indices and totals

[Mark Doll]

Hi Micheal!

Michael Smith schrieb:
> On 7/11/05, Mark Doll <doll at tm.uka.de> wrote:
> 
>>Hi all!
>>
>>I've read http://reactor-core.org/ogg-tagging.html and
>>http://www.vorbis.com/ot/20030303.html#id2726753 about the goals and
>>non-goals of vorbis comments, but I'm still unsure:
> 
> 
> You should note that the reactor-core document is from a single guy
> unaffiliated with xiph, and we mostly disagree with him.

OK.

> We've basically taken a conservative approach with adding 'official'
> tags - because the system is flexible, people can use unofficial ones
> with no problems at all. If they become really widespread and seem to
> have real usefulness to them, of course, we'd adopt them.

That's what I assumed. But I hoped to find some others who might have 
similar needs, so that at least we could adopt a common solution.


>>1) Is it by purpose to forget about CDA's index feature because it's so
>>rarely used or did nobody here ever thought about it?
>>-> Add an INDEXNUMER field?
> 
> 
> As you've noted, it's rarely used - care to explain what it actually is/does? 


On most CDs you'll only find index 0 and 1. Index 0 comprises the 
"pregap", normally digital zero (silence), that is played between the 
preceding track and the actual one. On a stand alone CD player, the time 
counter shows negative values. The music then starts at index 1 and the 
time displayed at index 1 is 0:00. When burning in track at once mode 
the default pregap is two seconds of digital zero (silence).

But somethimes
- the pregap isn't empty
- there are more indices besides 0 and 1

The first case (sample album: Shakira: MTV unplugged):
Here, the applause between the songs is put into index 0. The index 0 on 
this album is about 10 to 20 seconds long (varying between tracks).

Another variant of this (sample album: Aerosmith: Pump) is comparable to 
the above, but uses idices 1 and 2 to seperate an intro from the main 
track. This is because the intro belongs to this track (while the 
applause of the above live album semantically belongs to the previous 
track).

The second case (sample album: Genesis: Invisible Touch):
Index 2 is used to further subdivide track 6 into two parts, so one can 
directly skip to part two of this track. Index 2 is at about 4:28 min 
from the start (index 1) of the track.

Depending on the number of Parts, more indices are used, for example 
Sonic Youth: Daydream Nation uses 3 indices for track 12 and The Alan 
Parsons Project: The Turn Of A Friendly Card uses 6 for track 5.

One extreme variant is Glenn Gould's "Bach: The Goldberg Variations" 
from 1982. There is only one track (since the Goldberg Variations are 
only one piece of music), which is further subdivided into 32 indices: 
Aria (the theme), 30 Variations of the aria and the reprise of the Aria.

Of course, since the new standalone players seldomly support to skip to 
indices, this has been more and more replaced by using serveral tracks 
instead.

Besides those indices already added by the manufacturer of the CD, I 
occasionally use "hand made" indicees for hidden tracks. I own quite 
many CDs, where the last track of a CD consists of the main track, a 
(more or less long) period of silence followed by the bonus/hidden 
track. I then add index 2 (start of the silence) and index 3 for the 
start of the bonus track, so that I can play the bonus track directly or 
can omit the silence when playing the song during a party.

Mark.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 264 bytes
Desc: OpenPGP digital signature
Url : http://lists.xiph.org/pipermail/vorbis/attachments/20050711/e356ef54/signature.pgp