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ReplayGain2, ReplayGain2 proposal
jukkap
post Jul 23 2011, 16:33
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I suggest we discuss about possibility of creating ReplayGain2 specification that would replace the current ReplayGain.

ReplayGain2 would be playback compatible with the current ReplayGain (all current ReplayGain compatible players would work), but it should use ITU-R BS.1770/EBU R128 to calculate gain levels.

Current ReplayGain algorithm is odd and difficult and not properly specified. It also does not work for multichannel audio. ITU-R BS.1770/EBU R128 would overcome these issues.







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2Bdecided
post Aug 5 2013, 11:35
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ReplayGain developer


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Member No.: 409



Writing ReplayGain track and album gain tags with an intentionally different reference loudness is a very bad idea. It breaks existing players.

It is fine to use a new calculation method with a new reference loudness, but the values must be converted to the original reference loudness before being written to ReplayGain tags. That way, loudness matching will work on all ReplayGain compatible players across all ReplayGain tagged files.

An extra tag can be used to tell new players how to convert back to the new calculations' reference level if required, without breaking compatibility with old players. That way, you get the best of all worlds.

Consider an album with a loudness of -17 LUFs containing a track with a loudness of -16 LUFs
Assuming the 5dB conversion is used (i.e. assuming -23LUFs is 5dB quieter than the (83+6)dB SPL reference of ReplayGain), then...

This is good...
REPLAYGAIN_TRACK_GAIN=-2.0 dB
REPLAYGAIN_TRACK_PEAK=1.0000
REPLAYGAIN_ALBUM_GAIN=-1.0 dB
REPLAYGAIN_ALBUM_PEAK=1.0000
REPLAYGAIN_ALGORITHM = EBU R128
REPLAYGAIN_CONVERT_TAG_VALUES_BACK_TO_THAT_ALGORITHM = -5 dB
(might need to think of a better name for that tag wink.gif )

While this is bad...
REPLAYGAIN_TRACK_GAIN=-7.0 dB
REPLAYGAIN_TRACK_PEAK=1.21822226
REPLAYGAIN_ALBUM_GAIN=-6.0 dB
REPLAYGAIN_ALBUM_PEAK=1.21822226
REPLAYGAIN_ALGORITHM = EBU R128
REPLAYGAIN_REFERENCE_LOUDNESS = -23.00 LUFS


The idea is that existing players should work as they always have, while new players have the option of doing something different.

If you write track and album tags to a new reference level, but only mention that new reference level in a new tag which existing players ignore, you prevent all existing players from using those ReplayGain tags to match loudness. This is a bad thing.

Cheers,
David.

P.S.
EBU R128 GAIN = REPLAYGAIN_TRACK_GAIN + REPLAYGAIN_CONVERT_TAG_VALUES_BACK_TO_THAT_ALGORITHM
EBU R128 loudness = -23 -(REPLAYGAIN_TRACK_GAIN + REPLAYGAIN_CONVERT_TAG_VALUES_BACK_TO_THAT_ALGORITHM)
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Posts in this topic
- jukkap   ReplayGain2   Jul 23 2011, 16:33
- - mobyduck   http://www.hydrogenaudio.org/forums/index....showt...   Jul 23 2011, 16:40
- - Notat   This has been discussed. I believe there's act...   Jul 23 2011, 17:36
- - C.R.Helmrich   QUOTE (jukkap @ Jul 23 2011, 17:33) Repla...   Jul 23 2011, 18:10
- - jukkap   So that is the way to go. I suggest someone will c...   Jul 23 2011, 18:40
- - nazgulord   If I may ask, how different are gain values betwee...   Jul 23 2011, 23:16
- - db1989   R128 versus ReplayGain   Jul 23 2011, 23:31
- - Notat   I've been contacted by jaynyy and we've di...   Oct 8 2012, 22:55
- - Pat_   Suggestion for ReplayGain specification 2.0 ... I...   Aug 2 2013, 15:17
- - 2Bdecided   Writing ReplayGain track and album gain tags with ...   Aug 5 2013, 11:35
- - Pat_   QUOTE (2Bdecided @ Aug 5 2013, 11:35) It ...   Aug 6 2013, 11:01
|- - 2Bdecided   QUOTE (Pat_ @ Aug 6 2013, 11:01) I believ...   Aug 6 2013, 15:40
- - Case   Pbelkner's decision to write incompatible data...   Aug 6 2013, 13:42
|- - 2Bdecided   QUOTE (Case @ Aug 6 2013, 13:42) Pbelkner...   Aug 6 2013, 15:52
|- - pbelkner   QUOTE (Case @ Aug 6 2013, 14:42) Pbelkner...   Aug 6 2013, 17:17
- - [JAZ]   @pbelkner: When you designed and implemented your ...   Aug 6 2013, 20:09
- - Pat_   Hi Guys, It was not my intention to stir things u...   Aug 7 2013, 11:13
|- - 2Bdecided   QUOTE (Pat_ @ Aug 7 2013, 11:13) I believ...   Aug 8 2013, 11:31
|- - [JAZ]   QUOTE (2Bdecided @ Aug 8 2013, 12:31) No ...   Aug 8 2013, 15:48
- - Pat_   QUOTE (2Bdecided @ Aug 8 2013, 11:31) If ...   Aug 8 2013, 14:59
- - greynol   The reference level is calibrated to pink noise wi...   Aug 8 2013, 15:23
- - Pat_   QUOTE (greynol @ Aug 8 2013, 15:23) The r...   Aug 8 2013, 15:38
- - Pat_   QUOTE ([JAZ] @ Aug 8 2013, 15:48)...   Aug 9 2013, 14:47
- - 2Bdecided   Just to be 100% clear: you can use ReplayGain tags...   Aug 9 2013, 17:15


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