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

Ralph Giles <giles@thaumas.net> Wed, 27 August 2014 15:59 UTC

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Date: Wed, 27 Aug 2014 08:59:16 -0700
From: Ralph Giles <giles@thaumas.net>
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To: Ian Nartowicz <flac@nartowicz.co.uk>, codec@ietf.org
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Subject: Re: [codec] draft-ietf-codec-oggopus and "album" gain
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On 2014-08-27 7:30 AM, Ian Nartowicz wrote:

> This seems like a step backwards to me.  That MUST is a requirement
> that wasn't present before.  An earlier statement is "Virtually all players
> and media frameworks should apply it by default.", which I think is the
> appropriate guidance.

That's another one of those non-normative 'should' clauses we'd like to
resolve. The intention was that players MUST apply the gain; the
exception was for things like transcoders or DAW systems which could
propagate the gain without altering the decoded data. Can you think of
others?

I was trying to clarify that here, while leaving similar wiggle room in
the word 'respect'.

>> Is there a reason we shouldn't just have two examples?

Only brevity. The previous example used album gain because it was
offering guidance on how to record album gain in the absence of an
R128_ALBUM_GAIN tag. I switched to track gain because I thought that was
the more common normalization.

"Implementations of this specification MUST respect the 'output gain'
field, but MAY NOT respect the comments. Encoder authors are advised to
take this into account. For example, it is more robust for a
post-processing application to performing track normalization to update
the 'output gain' field and write a comment 'R128_TRACK_GAIN=0' than to
put the normalization value directly in the comment."

 -r