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

Ian Nartowicz <flac@nartowicz.co.uk> Wed, 13 August 2014 21:22 UTC

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Date: Wed, 13 Aug 2014 22:22:01 +0100
From: Ian Nartowicz <flac@nartowicz.co.uk>
To: codec@ietf.org
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Subject: Re: [codec] draft-ietf-codec-oggopus and "album" gain
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After much discussion on IRC, we've come up with some further clarifications to
the use of the output gain field and R128 tags.

In section 5.1:
        Virtually all players and media frameworks should apply it by
-       default.  If a player chooses to apply any volume adjustment or
-       gain modification, such as the R128_TRACK_GAIN, R128_ALBUM_GAIN
-       (see Section 5.2) or a user-facing volume knob, the adjustment
-       MUST be applied in addition to this output gain in order to
-       achieve playback at the desired volume.
+       default.  If a player chooses to apply any gain modification,
+       such as the R128_TRACK_GAIN or R128_ALBUM_GAIN (see Section 5.2),
+       the adjustment MUST be applied in addition to this output
+       gain in order to achieve playback at the normalised volume.


In section 5.2.1:
-   If an encoder wishes to use R128 normalization, and the output gain
-   is not otherwise constrained or specified, the encoder SHOULD write
-   the R128 gain into the 'output gain' field and store a tag containing
-   "R128_TRACK_GAIN=0".  That is, it should assume that by default tools
+   The encoder should assume that by default tools
    will respect the 'output gain' field, and not the comment tag.  If a
    tool modifies the ID header's 'output gain' field, it MUST also
    update or remove the R128_TRACK_GAIN and R128_ALBUM_GAIN comment tags

--ian