Re: [codec] draft-ietf-codec-oggopus and "album" gain

[Calvin Walton <[e-mail]>]

Hi, I noticed a typo in the diff; see the inline note below.

Note that I'm still of the opinion that there should not be any language
in the spec that explicitly disallows use of the REPLAYGAIN_*_GAIN tags
as implemented in Vorbis; the use of these tags in Ogg Opus is already
interoperable with many applications including Rockbox, GStreamer-based
players like Rhythmbox, and foobar2000 (when added manually via an
external tool).

Perhaps there should be something that states that if both R128_*_GAIN
and REPLAYGAIN_*_GAIN tags are present, the application should use
either one set or the other, but not attempt to apply both.

On Thu, 1970-01-01 at 00:00 +0000, Gregory Maxwell wrote:
> There have been a comments from a number of implementers that their
> applications would like to know if "album" gain adjustment had been
> performed on a track. An album gain is a feature the replaygain
> tagging has which allowed the dynamics within a collection of tracks
> to be preserved while still normalizing the collection overall.
> 
> Right now, the draft just recommends the encoder store it in the
> header gain field— which works okay but doesn't allow a player to know
> for sure which gain is being applied.
> 
> To clear this up I'm proposing we add a R128_ALBUM_GAIN which works
> just like R128_TRACK_GAIN and which can be set to zero when the header
> gain matches the album gain.
> 
> Here is a diff against the current draft:

[...]

> -An Ogg Opus file MUST NOT have more than one such tag, and if present its
> - value MUST be an integer from -32768 to 32767, inclusive, represented in
> +An Ogg Opus file MUST NOT have more than one of each tags, and if present
> + their values MUST be an integer from -32768 to 32767, inclusive,
> represented in
>   ASCII with no whitespace.
> -If present, it MUST correctly represent the R128 normalization gain relative
> - to the 'output gain' field specified in the ID header.
> -If a player chooses to make use of the R128_TRACK_GAIN tag, it MUST be
> - applied <spanx style="emph">in addition</spanx> to the 'output gain' value.
> +If present, REPLAYGAIN_TRACK_GAIN MUST correctly represent the R128

This should be "R128_TRACK_GAIN"

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-- 
Calvin Walton <[e-mail]>