On Thu, Aug 14, 2014 at 10:24:48AM -0700, Timothy B. Terriberry wrote: > >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 > > This was causing confusion because it suggested that an encoder should > _always_ prefer to put the track gain into the 'output gain' field. In > reality we used to have text saying that using the album gain for 'output > gain' was preferred, and this was just an alternative (the leading "If" > clause being the the important part of the sentence, not the SHOULD). > However, this sentence is entirely redundant with the text from the > definition of the 'output gain' field: "An encoder SHOULD set this field to > zero, and instead apply any gain prior to encoding, when this is possible > and does not conflict with the user's wishes." Removing the sentence avoids > the confusion. > > I've applied both sets of changes locally (using "An encoder" instead of > "The encoder"), and they'll be included in the next update (after WGLC). > > I also moved the "assume by default" sentence to the end of the paragraph > and removed the preceding paragraph break, as the warning about being > required to update the tags when the header value changes now logically > follows from the declaration that these tags are relative to that field.
So the patch applied for this part is now: > - 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 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 if present. > + An encoder should assume that by default tools will respect the 'output > gain' > + field, and not the comment tag. And I wonder two things about it: Is that intended to be "An encoder SHOULD assume"? And if we do want this to be normative, do we need to expand a little on what 'tools' and 'respect' means there - since that's possibly now less clear as a statement which stands on its own, rather than a(n intended) clarification to the text that is being removed. I agree with the rationale of what's intended by this change, but I'm less sure if it's now clear to a first time reader whether 'tools' includes both players and editors, and under what conditions the assumptions about 'default behaviour' will apply (since if we have the comment tags, obviously *something* might respect them sometimes). If we're going to give (normative) guidance there, it possibly wants to be a little more specific about what exactly it applies to. Ron _______________________________________________ codec mailing list [email protected] https://www.ietf.org/mailman/listinfo/codec
