[vorbis] ReplayGain support for Vorbis

[Moritz Grimm]

Wilson wrote:
> > Ummm... but the point in lossless coding is having the original back
> > after decoding it. Any alteration to that audio makes no sense to me.
> > Why don't you use Ogg at -q8 or higher instead (or mp+ --insane, if you
> I'm talking about 160GB hard drives here. A single one can hold almost 400
> CDs in FLAC format.

Oh, and you call those affordable?! For me and propably many others this
will be the case in 1-2 years, I guess.

Anyways, an affordable 60GB harddisk still has a lot of room, so I
accept this argument - although I could think of more useful ways to
fill it up (I ripped my CDs to able to conveniently enjoy them while
being at the computer, and this didn't make my CDs disappear as the
perfect archive).

> q9 Oggs are coming right up there on FLAC bitrates, so why not take the
> extra step and remove any possible ugly results? (udial.wav, even though

q9's nominal bitrate is 320kbps while I rarely get a better lossless
compression than x0.6 (~830kbps, with LPAC which is slightly better than
FLAC). Besides, what's the point in using Ogg Vorbis in the first place
if ugly results happen even at q9? udial.wav is no example - there is no
such thing as clipping in not totally braindead audio-masters. Ogg
Vorbis is definitely good enough now to be an alternative to lossless
coding - even for audiophiles (IMHO).

> can be certain that you won't "suddenly" start hearing an artifact when you
> upgrade your equipment. I'm sure q9 Ogg is good enough, but given the minor
> incremental cost of moving up to FLAC, it's an option I would like to have.
> Also, AFAIU, you can return to the "original" file with the ReplayGain
> system. Seems like a good fit with a lossless codec.

Using FLAC instead of Vorbis @ q9 reduces the amount of music on your
HDD by half or more, IMO not worth the (to me inaudible) gain of
quality. The noise of your harddisk and fans etc are louder (and
propably more annoying) than anything that could happen at q9 in Ogg and
not happen in FLAC.

I listen to music on a Sennheiser HD 590, and the rest of my equipment,
while not being high-end, also can be called "Hi-Fi". I don't fear any
bad surprises, even when I might upgrade somewhen in the far future.

> I'm having trouble thinking of a use for an Ogg file that has a Vorbis AND a
> FLAC stream. Help me out here?

Like Ogg FLAC, this is a hypothetical example that requires some tools
to be written first. This is science fiction:

After finishing a song I would encode the mixdown (might even be
24bit/96kHz some day, this is what you have before finally mastering it)
to
FLAC, and a q5 or q6 version of the mastered Vorbis stream (the one I'd
listen to myself and distribute on the Internet). Every time I wish I
can extract the encoded master from the .ogg file containing both
streams, and also peel it down on demand for previews or streaming. I
wouldn't archive the master as FLAC, because mastering is quite some art
in itself, and I would archive mistakes I wouldn't have made at a later
time (you never stop to learn). If I needed a lossless master, I'd burn
it to CD-A before deleting the .WAV after encoding to Vorbis.

The result would be a .ogg as a repository of everything I need. Who
knows, I might even be able to play that thing in Winamp using an
in_ogg.dll that supports all kinds of Ogg files and tell it to play the
highest-quality Vorbis stream by default.

To get back to replaygain, currently its values are stored in the Vorbis
comment field. So, every Vorbis stream in an .ogg file has its own
replaygain value. A global replaygain for all Vorbis streams and the
FLAC stream would break the thing - the FLAC mixdown would need
completely different values than the Vorbis master (in this example),
and different songs in multiple Vorbis streams would need different
replaygain values, too. Think of an .ogg file with an English and a
German track for an Ogg Tarkin videostream, for example.

If I wanted to play the mixdown, replaygain would be in the way as
volume is something I have to consider when thinking about how to make
the master. Apart from that, it's also about philosophy - for me,
lossless has a lot to do with Hi-Fi. No information may be lost, OTOH
nothing should be added as well. If the person who made the master
decided to have volume a certain way, it has to be so.

OK, so some people really want replaygain for every possible stream in
an .ogg file (including FLAC), but having one global replaygain for
everything wouldn't work with many of Ogg's possible features. I have no
idea whether my use of it has anything to do with the requirements of
professional studios, however, this is how I'd do it.

<p>Moritz


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