[Matroska-users] Question on ReplayGain tags

Johannes Weißl jargon at molb.org
Sat Feb 12 18:47:54 CET 2011


Hello Steve,

thanks for the clarification! I still think a text value would be so
much better, not just for supporting a single proprietary player:

* Tag can be displayed / edited, even if only simple tags are supported
  (which is so convenient with vorbistags as compared to e.g. id3, where
  many fields can only displayed/edited if they are supported).
  Right now it is only a hex64-blob in the tags xml file.
* I think the compact binary-style spec at replaygain.org was meant for
  much more inflexible formats than matroska, where we can easily add
  variable-length data because of the xml-like structure.
* Numeric values can be stored in arbitrary precision.
* Matroska doesn't need the first three bits (name code) at all, it
  would be confusing if the name code and the TargetType differ.
* The originator code isn't very important, nobody uses it. If we don't
  want to loose this information, a new text tag (REPLAYGAIN_ORIGINATOR)
  would be much more flexible.

The binary format has no advantages I can think of.

I think it is not too late to change the spec, especially because there
are almost none (if any?) implementations...
At least it is very easy to differentiate between binary/text because
the tags are typed.

Johannes


On Sat, Feb 12, 2011 at 10:00:12AM +0100, Steve Lhomme wrote:
> Yes the values are according to [2] as implied in the specs by the
> link to http://www.replaygain.org/
> 
> I'm not too thrilled to change the meaning in the specs just because
> one player decided to go its way without looking at the specs. At the
> very least foobar2000 should store the value in another tag than the
> ones that are clearly specified as binary. Also it seems the binary
> format offers many more information than just "+9.65 dB" for example
> if the gain was specified in the studio, by a user, etc.
> 
> We are going to introduce a new Matroska v3 (ie put 3 in the header)
> to get rid of legacies like that (and add new things). I suggest the
> foobar2k dev check this value and store it in binary from now on in v3
> files. So they can tell between current and future files the meaning
> of the REPLAYGAIN_GAIN and REPLAYGAIN_PEAK tag values.
> 
> Steve
> 
> On Thu, Feb 10, 2011 at 5:31 AM, Johannes Weißl <jargon at molb.org> wrote:
> > Hello list,
> >
> > I have a question on the replaygain tags in Matroska. The documentation [1]
> > states that the type of REPLAYGAIN_GAIN and REPLAYGAIN_PEAK is "binary".
> > Does this mean that the value should be stored according to the Replay
> > Gain Data Format [2]? I don't know if that makes much sense, since this
> > format encodes a "name", which is redundant since Matroska has something
> > similar using TargetType. The only existing program I could find which
> > writes those tags is foobar2000, and it stores the values as UTF-8 text
> > (e.g. "+9.65 dB").
> >
> > [1] http://www.matroska.org/technical/specs/tagging/index.html
> > [2] http://replaygain.hydrogenaudio.org/rg_data_format.html
> >
> >
> > Greetings,
> > Johannes
> >
> > _______________________________________________
> > Matroska-users mailing list
> > Matroska-users at lists.matroska.org
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> >
> >
> 
> 
> 
> -- 
> Steve Lhomme
> Matroska association Chairman
> _______________________________________________
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> Matroska-users at lists.matroska.org
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