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Topic: Software to compare waveforms - Lossless vs. Compressed (Read 2181 times) previous topic - next topic
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Software to compare waveforms - Lossless vs. Compressed

I know there must be software that lets me subtract compressed from lossless and show me a distribution of what information is left. Can anyone please give me a name and a source? Thank you.

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #1
Although there is probably software that will let you do this, you can't learn anything particularly useful from doing it, so I'd advise you to not spend any time on it. As per TOS8, you hear with your ears, not your eyes.

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #2
Subtracting wave forms shows differences of data, not differences of information.

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #3
'tis as pointless as trying to point out differences between two image file formats of an identical photograph by comparing their respective histograms.
Listen to the music, not the media it's on.
União e reconstrução

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #4
Audacity.
Import lossless and lossy track, invert one track, mix and render.
Audio needs to be aligned.

I will simply quote Aleron.
you can't learn anything particularly useful from doing it
gold plated toslink fan

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #5
Check out DeltaWave.

https://deltaw.org/

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #6
This is redundant but, "The sound OF the difference is not the same as the difference IN the sound."

If you do a simple subtraction and you get silence, yes...  That DOES prove there is no difference but it doesn't work the other way around...

The most obvious example is if you create a slight delay by adding a few milliseconds of silence to the beginning of one copy.   The files sound identical but when you subtract you get a LOUD difference file with "phasing" (comb filtering).    The comb filtering is a "clue" indicating a delay but of course that's meaningless because when played separately there is no comb filtering and no difference, and of course there's a "delay" anyway if you aren't playing both files at the same time,

In fact, MP3 and AAC do add a little delay,  That can be taken-out before subtracting but it's just the most obvious "data difference" that doesn't necessarily affect the sound.    

There's also the fact that you can hear differences alone that you can't hear when those differences are drowned-out by the music.      In concept, it's similar to a slight background noise that you can hear when there is no music but not while the music is playing.



P.S.
It would be possible to make an MP3 or AAC encoder that makes the regular compressed file plus a file of whatever was "thrown away".    This has probably already been done as part of the software development.   But there are other "imperfections" in the process such as FFT and reverse FFT where you can't really save what's been changed or "lost".

P.P.S.
People often compare the spectrum of an MP3 with the lossless original to see the difference.   But with high-quality MP3s, if you hear a compression artifact it's usually not the loss of high frequencies that you hear.

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #7
The most obvious example is if you revert polarity. The difference becomes ... same signal but double.

(That gets you a free music maker! Start with music X, lose not only X but even Y = 2X; what remains is Z = original signal minus loss = X- Y, and Z is still completely transparent to X.  Imagine that, you can give away two X signals to your friends and still be left with something that is just as good - how do I translate that procedure to cake and cash?!  ;D )

P.S.
It would be possible to make an MP3 or AAC encoder that makes the regular compressed file plus a file of whatever was "thrown away".    This has probably already been done as part of the software development.

Lossy + correction file? David Bryant of WavPack coined the phrase hybrid lossless for that ;-)
And yes it has been done with the formats you mention: MP3HD and MPEG4-SLS, respectively. Much to the enthusiasm of ... nobody in particular. But the principle is in use: DTS-HD.

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #8
Honestly, it's an interesting thing to do, if you don't plan on using it as a means to judge the particular format/encoder but purely for curiosity, to perceive what is otherwise (at least in the case of transparency) imperceptible - what is the added noise that is otherwise (hopefully) entirely masked by the original sound? It can be entertaining to learn just how much our ears/brains are capable of not hearing, by isolating the noise that you otherwise don't hear.



Re: Software to compare waveforms - Lossless vs. Compressed

Reply #11
no build for windows?
It says that 0.8.4 will be built for Windows later, that 0.8.3 was OS X specific bugfix, and that 0.8.2 ...  https://github.com/alexkay/spek/releases/download/v0.8.2/spek-0.8.2.msi

 

Re: Software to compare waveforms - Lossless vs. Compressed

Reply #12
You must have the original version to compare.

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