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How/why does lossy encoding alter peak amplitude/increase it beyond 1?, [was “cdparanoia Peak Limiting?” in CD Hardware/Software]
etrask
post Jul 14 2013, 02:47
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Hello all, first post, sorry if this isn't the right sub-forum. I couldn't find this addressed anywhere.

I noticed something odd recently. I ripped a track using cdparanoia, and when I have foobar2000 do a ReplayGain scan on the output WAV file, it prints the info as:
Track gain: -9.68 dB
Track peak: 1.000000

Encoding the output WAV with oggenc2 and having foobar2000 do a RG scan I get:
Track gain: -9.62 dB
Track peak: 1.253938


This seemed odd to me so I looked at other CDs I'd ripped with cdparanoia and FLAC-encoded, and noticed the Track/Album peaks never went over 1.000000, but that lossy-encoded files of those same songs frequently did. I admit I'm an amateur when it comes to audio but this doesn't make sense to me. How can the peak be so different from the lossless file to the lossy file? I guess I just don't understand exactly how RG (or WAV files) works...



Software I'm using:
cdparanoia III release 10.2 (September 11, 2008) from the Debian 7 repository
flac/metaflac 1.2.1 from the Debian 7 repository
OggEnc v2.87 (LancerMod(SSE3) based on aoTuV b6.03 [20110424]) from rarewares.org
foobar2000 v1.2.8 on Windows 7
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gib
post Jul 14 2013, 03:44
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This recent thread is essentially about the same thing. Post #3 by carpman pretty much covers what you're wondering.
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db1989
post Jul 14 2013, 10:53
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Why does your title implicate cdparanoia in this? You seem to conclude in the body of your post that the lossy encoder is responsible, and yet your title suggests otherwise.

Anyway, as linked, this is totally normal during lossy encoding. And with reference to cdparanoia, one would assume it avoids limiting and all other audio-altering processes by default due to its stated aim of completely accurate extraction, Therefore, I guess your CD was simply limited in the mastering stage.
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etrask
post Jul 14 2013, 18:22
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Thanks guys! The linked thread is informative


QUOTE (db1989 @ Jul 14 2013, 02:53) *
Why does your title implicate cdparanoia in this? You seem to conclude in the body of your post that the lossy encoder is responsible, and yet your title suggests otherwise.

Anyway, as linked, this is totally normal during lossy encoding. And with reference to cdparanoia, one would assume it avoids limiting and all other audio-altering processes by default due to its stated aim of completely accurate extraction, Therefore, I guess your CD was simply limited in the mastering stage.


I at first assumed cdparanoia was limiting the peak since I was certain the CD peaked above that (it's loud and compressed)... but of course that doesn't make sense since that peak is a comparison to "digital full scale", so it can't possibly go over 1.0. Didn't mean to imply anything negative about cdparanoia
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