[flac-dev] R128gain & metaflac

Timothy B. Terriberry tterribe at xiph.org
Wed Jun 18 17:56:01 PDT 2014

Ian Nartowicz wrote:
> It is certainly the biggest issue.  Sure it should be simple to address, but
> nobody seems willing to do so.  The only response I've had so far is that the
> output gain should *always* be applied, yet it *might* be an album gain.  It
> can't be both and there is no way to tell which.  Sorry, but that makes it

Well, make a proposal on the IETF list that addresses this (the FLAC 
list probably isn't the right place for this discussion). So far the 
only discussion there has been "I think this is broken but I don't know 
what to do," and, "I don't think the IETF should be allowed to say what 
goes in the tags of an Ogg Opus file."

This could be as simple as just adding another tag which says whether or 
not the header gain is an album gain.

The issue the header gain was trying to solve is that something close to 
half of all software that plays Vorbis completely ignores replaygain 
tags. So if you tag a file you have literally no idea what volume a 
player will play it back at compared to an untagged file.

> The second issue is the lack of defined peak tags.  I could care less, but some
> people care deeply and it is a relatively standard feature of music players.
> The Opus spec doesn't define such tags, but it does explicitly say not to use
> the REPLAYGAIN* tags.  Again that's just not viable.

The only usage we could find of the peak tags in the wild was people 
doing crazy things, like limiting the gain they applied so the peak 
could not go above 1.0 (which makes the actual gain stored in the file 
useless, and, like above, destroys the predictability about what volume 
a file will be played back at, since very little software looks at these 
tags at all). If you do any kind of resampling they're not reliable 
anyway, so there did not seem to be any point to add them (and adding 
them seemed actively harmful).

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