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Why can mp3 go above 1.0 peak when other formats cant?
CoyoteSmith
post Aug 5 2010, 13:05
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i have noticed many of the mp3s i download from archive.org (Creative Commons) go above the 1.0 Track Peak according Replay Gain, however i have not been able to notice this in other formats. when rendering audio losslessly it clips, why/is mp3 an exception?
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lvqcl
post Aug 5 2010, 13:16
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AAC, Vorbis, Musepack, AC3 can also have replaygain_track_peak > 1.0
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saratoga
post Aug 5 2010, 16:36
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QUOTE (CoyoteSmith @ Aug 5 2010, 08:05) *
i have noticed many of the mp3s i download from archive.org (Creative Commons) go above the 1.0 Track Peak according Replay Gain, however i have not been able to notice this in other formats. when rendering audio losslessly it clips, why/is mp3 an exception?


All lossy formats do this if they're peak normalized.
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2Bdecided
post Aug 5 2010, 17:37
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QUOTE (saratoga @ Aug 5 2010, 16:36) *
All lossy formats do this if they're peak normalized.
i.e. if the original was peak normalised, then when you encode it lossy-ly, some of the peaks get pushed higher.

Most lossy formats are floating point internally, so they can cause values to be reconstructed that are far higher than the defined 0dB FS.

Cheers,
David.

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AndyH-ha
post Aug 6 2010, 00:36
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Uncompressed wav can do the same thing -- much higher peak that 0dB coming out the DAC if the DAC has adequate headroom.
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