[vorbis] Quality & Tags

[Moritz Grimm]

"David K. Gasaway" wrote:
> Instead, I'll just ask a question.  What happens to this tag when the stream is peeled?

Hmwell, since the encoder sets this tag, not the user, it could simply
replace it with the new settings. Peeling down a stream isn't like
reencoding, there should be almost no unnecessary loss so the new values
would make sense. No need for multiple encsetting tags here. (Can this
tag be set by libvorbis, btw?)

The problem I see is more about what this tag actually would tell us.
Yes, it says that a tune is encoded in -q 8 for example, but what if the
encoded song itself totally sucks? Even a "source" tag couldn't explain
why certain tunes I get to hear sound so very bad. Here's an extreme
example, with an imaginary standard-tag called "source":

ource=Vinyl
source=US$ 6 microphone used to record from a grammophone
source=WMA @ 96kbps
source=Xing MP3 @ 112kbps (WMA suxxx!!)
source=mangling, chopping and corrupting on Kazaa
source=CoolEdit filtering (to get rid of some clicks, glitches and
noise)
source=lame @ 192kbps
source=CD
encsettings=-q 8

Whether "encsettings" or similar would have any meaning is in the hands
of fate. The result of a song with this history could be underpitched
and then resold as an experimental ambient soundscape, I suppose. The
last two source tags wouldn't explain any horrible quality either, and I
doubt that anyone could possibly tag an Ogg file that way anyways -
nobody knows what happens to the poor music unless one rips and encodes
by oneself.

ENCSETTINGS makes most/only sense when the encoded file doesn't go
through any p2p network(s). It'd be there to classify the own music
collection, and it might be useful for some advocating (look how good
this sounds, and it's -q 2!). It might be an indirect hint on how good a
rip is because you know what you can expect from a certain setting. It
still does not say anything about a tune unless you were able to
actually hear it.

The question is whether this information is valuable enough to make it a
standard. If not, I suggest people who need it define it by themselves.

<p>Moritz


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