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Dense newbie question about LossyWAV
Wally Walters
post Dec 6 2010, 20:12
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I read the wiki and several threads here, but I'm still not clear on the following two questions:

1. If LossyWAV is not lossless, what exactly is lost?
2. How does the audio signal produced by LossyWav differ from the original audio signal?

Sorry for my poor English, I'm a product of the U.S. education system.

Thanks!

This post has been edited by Wally Walters: Dec 6 2010, 20:13
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mjb2006
post Dec 7 2010, 03:20
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A slightly less technical explanation, possibly inaccurate (someone correct me if it is): All that's being lost are the bits that provide the lowest-amplitude (quietest) variations in the signal. Strategically zeroing those bits makes the quietest sounds (already probably masked by the loud sounds) be totally silent. Having all n LSBs zeroed in every sample in a block (1 block = 4096 samples by default, in FLAC) results in a huge space savings in that block, because of the way FLAC happens to handle that kind of signal. There's no need for the codec to store data for reconstructing 16-bit samples if the lowest n bits are all zero; it can instead just deal with 16-minus-n-bit samples, and then shift them after decoding. (Well, that's in effect; I don't pretend to know what actually goes on in the encoder). n will vary from block to block depending on how much noise/inaccuracy would be introduced by zeroing more bits. The goal is to zero as many as possible while keeping the imprecision below an audible threshold, the standard target being the signal's noise floor. For most music you're not going to be losing any musical signal. I'm curious to know if anyone has actually found any ABX-able examples yet.

This post has been edited by mjb2006: Dec 7 2010, 03:23
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Wally Walters
post Dec 7 2010, 04:17
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So how different would the reconstructed LossyWAV file look from the original?
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mjb2006
post Dec 7 2010, 05:03
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QUOTE (Wally Walters @ Dec 6 2010, 20:17) *
So how different would the reconstructed LossyWAV file look from the original?

Do you listen with your eyes? smile.gif 0.5% different, 5% different, 50% different...who cares, as long as the difference isn't audible?
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Wally Walters
post Dec 7 2010, 07:58
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Just curious how close the reconstructed signal is to the original.
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Posts in this topic
- Wally Walters   Dense newbie question about LossyWAV   Dec 6 2010, 20:12
- - Nick.C   Hi there, 1) lossyWAV exploits a feature of FLAC,...   Dec 6 2010, 20:21
- - Fandango   It kinda looks like this:   Dec 7 2010, 02:52
- - mjb2006   A slightly less technical explanation, possibly in...   Dec 7 2010, 03:20
|- - Wally Walters   So how different would the reconstructed LossyWAV ...   Dec 7 2010, 04:17
||- - mjb2006   QUOTE (Wally Walters @ Dec 6 2010, 20:17)...   Dec 7 2010, 05:03
||- - Wally Walters   Just curious how close the reconstructed signal is...   Dec 7 2010, 07:58
|- - chrizoo   QUOTE (mjb2006 @ Dec 7 2010, 03:20) A sli...   Sep 13 2011, 08:00
|- - Northpack   QUOTE (chrizoo @ Sep 13 2011, 08:00) QUOT...   Sep 13 2011, 09:26
|- - mjb2006   By quietest sounds, I didn't mean quiet passag...   Sep 13 2011, 10:10
|- - Northpack   QUOTE (mjb2006 @ Sep 13 2011, 10:10) By q...   Sep 13 2011, 10:30
|- - saratoga   QUOTE (mjb2006 @ Sep 13 2011, 05:10) By q...   Sep 13 2011, 18:53
- - Nick.C   Try processing a file and use the --correction par...   Dec 7 2010, 08:41
- - Rotareneg   There isn't a "reconstructed signal,...   Dec 7 2010, 08:45
- - Wally Walters   Toldja I was dense. But I think I understand bett...   Dec 7 2010, 19:25
- - [JAZ]   Let's see if this explanation is easier to und...   Dec 7 2010, 19:48
|- - bandpass   Seems a bit odd to name an algorithm after a conta...   Aug 8 2011, 10:14
- - Nick.C   In retrospect, it may have been better to use a na...   Aug 8 2011, 17:30
- - lvqcl   After all, it's *.lossy.wav   Aug 8 2011, 17:39
- - mjb2006   Thanks for correcting my mistaken simplifications,...   Sep 13 2011, 21:23


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