[CJG888]

I have heard a rumour that ALAC, unlike FLAC, is not genuinely lossless, but uses an element of lossy compression. Does anyone know if this is true? I really don't want to have to re-rip all my CDs...

 

[castleofargh]

you're asking us if you should re-rip all your albums based on a rumor? I would be tempted to say no ^_^.

 

[jfaaz]

ALAC is lossless.  You can convert ALAC to FLAC, APE, AIFF, or WAV as much as you want and not lose any quality.  As far as which lossless format sounds better, that is up to your ears.

 

[justaname]

http://www.head-fi.org/t/738552/testing-the-claim-i-can-hear-differences-between-lossless-formats

Some people have super hearing though...

I leave some of the better albums on flac, for peace of mind, even though I probably couldn't tell the difference on foobar.

 

[esldude]

You can take FLAC, ALAC, and WAV send them over an SPDIF connection and capture the resulting digital data stream.  Them compare those three to see if even a single bit has changed value.  I have done this and all three are bit for bit identical.  So no reason to re-rip anything. 

 

[Music Alchemist]

http://www.head-fi.org/t/738552/testing-the-claim-i-can-hear-differences-between-lossless-formats

Some people have super hearing though...

I leave some of the better albums on flac, for peace of mind, even though I probably couldn't tell the difference on foobar.

 
Wow, I randomly go to this thread and a thread I started is mentioned.

 

 

[stv014]

  You can take FLAC, ALAC, and WAV send them over an SPDIF connection and capture the resulting digital data stream.

 
A simpler method is to decode the FLAC or ALAC back to WAV, and compare the files. They should be identical if all have only the basic 44 bytes WAV header.

 

[StudioSound]

I originally ripped my library to FLAC.
Then I converted it to ALAC a number of years ago when I was using a lot of Apple hardware.
I converted it back to FLAC earlier this year.

Everything still verifies against the AccurateRip database. It's totally lossless.

 

[esldude]

   
A simpler method is to decode the FLAC or ALAC back to WAV, and compare the files. They should be identical if all have only the basic 44 bytes WAV header.

Yes, and of course rather than doing it a handful of times that is what I do.  But then some have complained (quite irrationally) that the files might be the same while sending different bits over the connection with some errors due to some imagined problem.  Doing a few over a connection answered any conceivable complaints about how the result might differ. 

 

[stv014]

 
Yes, and of course rather than doing it a handful of times that is what I do.  But then some have complained (quite irrationally) that the files might be the same while sending different bits over the connection with some errors due to some imagined problem.  Doing a few over a connection answered any conceivable complaints about how the result might differ. 

 
That is a different issue, though, the OP was apparently only interested in knowing if lossless compression is really lossless (i.e. bit perfect), which it obviously is, barring software bugs or hardware failures. The encoding/decoding libraries for these formats are also fairly old and well debugged. Player software normally will not implement decoding from scratch, but use the existing and freely available libraries. The FLAC encoder even validates the compressed stream by decoding it in memory and verifying the checksum (computed from the original raw PCM data), which is also stored in the FLAC file.
 
Concerns regarding audible differences between binary identical PCM streams read or decoded from different lossless files are most often based on "software induced jitter". Those who believe in that can often not be convinced by any counter-arguments, and will not accept ABX as evidence either.

 

[esldude]

   
That is a different issue, though, the OP was apparently only interested in knowing if lossless compression is really lossless (i.e. bit perfect), which it obviously is, barring software bugs or hardware failures. The encoding/decoding libraries for these formats are also fairly old and well debugged. Player software normally will not implement decoding from scratch, but use the existing and freely available libraries. The FLAC encoder even validates the compressed stream by decoding it in memory and verifying the checksum (computed from the original raw PCM data), which is also stored in the FLAC file.
 
Concerns regarding audible differences between binary identical PCM streams read or decoded from different lossless files are most often based on "software induced jitter". Those who believe in that can often not be convinced by any counter-arguments, and will not accept ABX as evidence either.

While you are correct about not convincing people who just want to believe otherwise (99% probably), I did convince two people.  They insisted something was different in FLAC and WAV etc. etc.  I just started at the beginning with their imagination backing up one step about what could be going on all the way.  When it got to the very end a couple finally said there must be nothing to it.  So sometimes going the extra step will help although at least 50 other people weren't convinced and won't be.
 
Of course I usually just do a checksum comparison if I am wondering if some process is bit perfect/bit transparent. 

 

[castleofargh]

last time I had someone thinking the same thing about wave vs flac in front of me, instead of trying to explain why it is the same, I asked him to explain to me how he imagined the audio process to work. and surely enough he was thinking that somehow DAC chips were clever multilanguage machines or that even one DAC was used for each codec. after maybe 3 or 4 misconceptions proved to be wrong thank to internap(because obviously he would believe internet more than me), he gave up and admitted his reasons to believe there was a difference were false ones. and surely enough, a few weeks later he had turned his waves into flacs.
I was lucky to have someone able to listen, understand, and accept the possibility of being wrong without ego struggles. if I tried that with my mother, she would listen to the first 2 sentences and then go into homer Simpson's mod

.

 
I love you mum!!!!!

 

[BackToAnalogue]

It's an easy mistake to make. It won't take you long to find a post from someone saying that FLAC has different compression levels and so if you use a higher level it gets more lossy. That is totally incorrect of course as is all the stuff about different players (Foobar, VLC whatever) having different sound characteristics. So all most people are doing is repeating what they have read somewhere or indeed in several places or they have been told by a friend or colleague, and they assumed it was correct. I have made that mistake myself quite a few times and not just on forums talking about audio. I have made that mistake in a very big way indeed on a couple of occasions.