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iTunes does not rip accurate audio data - Page 2

post #16 of 199
1/28/08 at 11:51pm
Thread Starter 
Quote:
Originally Posted by dkjohnso View Post
Aren't you comparing a WAV to an M4A there? Perhaps I am missing something. But of course those files are going to be very different: one is compressed one isn't. Decode that M4A to a WAV and compare the WAV files.
Ok, will do. Sorry about that.
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post #17 of 199
1/28/08 at 11:52pm
Quote:
Originally Posted by dkjohnso View Post
Aren't you comparing a WAV to an M4A there? Perhaps I am missing something. But of course those files are going to be very different: one is compressed one isn't. Decode that M4A to a WAV and compare the WAV files.
That shouldn't be necessary. What he has is ALAC in an M4A container which should be lossless.

iTunes does NOT do secure ripping (at least on a PC), which means it does not know if what the CD drive is reading is bit-accurate. Someone makes a good point here though:
ALAC and iTunes, is it a secure rip? - iPod - iPhone - iTunes Forums at iLounge
On a Mac, iTunes is never faced with an unfamiliar drive, therefore it may be set up on OS X to be bit-accurate with the Mac optical drives
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post #18 of 199
1/28/08 at 11:55pm
IPodPJ, you are obviously doing something wrong when encoding.

EAC does not have a built-in FLAC encoder. It uses the user-defined external encoder for FLAC files. The "bitrate" drop-down on the "Compression options" has no effect when using an external encoder.

I just tested this myself to be sure:

Take It Easy - encoded using EAC/FLAC external encoder with the "bitrate" option set to 32kbps.

Take It Easy 2 - encoded using EAC/FLAC external encoder with the "bitrate" option set to 1024kbps.

Other command line options: -6 -V -T "ARTIST=%a" -T "TITLE=%t" -T "ALBUM=%g" -T "DATE=%y" -T "TRACKNUMBER=%n" -T "GENRE=%m" -T "COMMENT=%e" %s -o %d

Here is the result from Foobar bit-compare:

Quote:
Comparing:
"C:\MED_Docs\Music\01 Take It Easy 2.flac"
"C:\MED_Docs\Music\01 Take It Easy.flac"
No differences in decoded data found.
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post #19 of 199
1/28/08 at 11:59pm
Thread Starter 
Here are the results after converting the M4A (ALAC) file to a WAV:

Comparing:
"C:\Users\Phil\Desktop\Vivaldi_ Four Seasons\01 Vivaldi_ Four Seasons, Op. 8_1, R.wav"
"C:\Users\Phil\Music\EAC extracted music\Antonio Vivaldi\The Four Seasons\Antonio Vivaldi - The Four Seasons Op. 8 - 01 - La Primavera (the Spring), Allegro.wav"
differences found: 16987797 sample(s), starting at 2.1626531 second(s), peak: 0.9897766 at 20.1665760 second(s), 1ch

Identical results. So apparently Foobar uncompresses the ALAC data anyway before it does a bit-compare.
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post #20 of 199
1/29/08 at 12:00am
I was wrong, see below.
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post #21 of 199
1/29/08 at 12:02am
Quote:
Originally Posted by IPodPJ View Post
Here are the results after converting the M4A (ALAC) file to a WAV:

Comparing:
"C:\Users\Phil\Desktop\Vivaldi_ Four Seasons\01 Vivaldi_ Four Seasons, Op. 8_1, R.wav"
"C:\Users\Phil\Music\EAC extracted music\Antonio Vivaldi\The Four Seasons\Antonio Vivaldi - The Four Seasons Op. 8 - 01 - La Primavera (the Spring), Allegro.wav"
differences found: 16987797 sample(s), starting at 2.1626531 second(s), peak: 0.9897766 at 20.1665760 second(s), 1ch

Identical results. So apparently Foobar uncompresses the ALAC data anyway before it does a bit-compare.
Hmmm....well then I must admit I have no idea what is going on. I suspect one of your encoders is not working properly, but it is way past my bedtime....

Edit: My mistake, foobar comparator does indeed compare the decoded data.
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post #22 of 199
1/29/08 at 12:05am
Quote:
Originally Posted by dkjohnso View Post
It will matter. Lossless files are still compressed and thus will look very different from the WAV files they were created from. It is analogous to a document and that same document in a ZIP.
Foobar compares audio data, not the file themselves
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post #23 of 199
1/29/08 at 12:06am
Thread Starter 
Quote:
Originally Posted by Febs View Post
IPodPJ, you are obviously doing something wrong when encoding.

EAC does not have a built-in FLAC encoder. It uses the user-defined external encoder for FLAC files. The "bitrate" drop-down on the "Compression options" has no effect when using an external encoder.

I just tested this myself to be sure:

Take It Easy - encoded using EAC/FLAC external encoder with the "bitrate" option set to 32kbps.

Take It Easy 2 - encoded using EAC/FLAC external encoder with the "bitrate" option set to 1024kbps.

Other command line options: -6 -V -T "ARTIST=%a" -T "TITLE=%t" -T "ALBUM=%g" -T "DATE=%y" -T "TRACKNUMBER=%n" -T "GENRE=%m" -T "COMMENT=%e" %s -o %d

Here is the result from Foobar bit-compare:
Ok, that's good to know. I am not familiar with FLAC as I don't usually use it for anything. But that FLAC decoder came with EAC and doesn't have any level 1 - 8 options. I'd still like to know why there are so many different options if they have no affect of audio playback. No one wants to take up more hard drive space than necessary, so if they all yield the same audio playback result, there is no point in having 8 options.

My main concern was why iTunes is changing the audio data when it rips to either ALAC or WAV. A difference of 16.9 million samplesis not what I would call anywhere near to lossless. I maintain (and have for quite some time) that CD-DA uncompressed sounds better and recommend anyone who cares about audio quality to avoid lossless compression. It is now obvious that different encoders use different algorithms that can drasticaly alter the audio data.
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post #24 of 199
1/29/08 at 12:08am
Quote:
Originally Posted by TMM View Post
Foobar compares audio data, not the file themselves
Indeed, I have edited my posts above to reflect this.

However, I still think the issue here is not whether FLAC and ALAC are lossless codecs: encoding a WAV into lossless then decoding again will yield an identical WAV. What is happening here is that the audio stream is becoming corrupted along the way somehow. I hope that the OP can get to the bottom of it.
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post #25 of 199
1/29/08 at 12:08am

del


Edited by servoled - 4/11/11 at 7:52pm
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post #26 of 199
1/29/08 at 12:17am
Thread Starter 
Quote:
Originally Posted by servoled View Post
I'm fairly sure you are doing something wrong. I just ripped a track in iTunes to ALAC and WAV and compared them in foobar:

Code:
Comparing:
"J:\iTunes\Roky Erickson\Don't Slander Me (Reissue)\01 Don't Slander Me.wav"
"J:\iTunes\Roky Erickson\Don't Slander Me (Reissue)\01 Don't Slander Me.m4a"
No differences in decoded data found.
Please go back and read the posts from the beginning of the thread. I never said that an iTunes' extracted WAV or ALAC will sound different from eachother. What I said (and proved) was that an iTunes' extracted WAV or ALAC are different from WAV files extracted with EAC.
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post #27 of 199
1/29/08 at 12:19am
Quote:
Originally Posted by IPodPJ View Post
I never said that an iTunes WAV or ALAC will sound differently.
Yes, you did. That is exactly what you said. Your thread is titled "ALAC is not lossless," and you said:

Quote:
I put in a classical CD today that my neighbor loaned me, Antonio Vivaldi, Four Seasons. When I played it straight from my computer's CD player it sounded fantastic. Then I encoded it in ALAC through iTunes (as I have done with most albums in the past, even though I play them through Foobar) and it sounded like garbage. All the high end was missing. And it wasn't semi-obvious. It was so obvious a 90% deaf person could tell the difference. Even the little spectrum analyzer in Foobar was not bouncing up and down at more than half of the way from left to right. But when the CD was playing, the spectrum analyzer was bouncing up and down all the way from left to right (20Hz - 20kHz). So obviously iTunes' ALAC encoding rolls off a ton of audio data.
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post #28 of 199
1/29/08 at 12:20am

del


Edited by servoled - 4/11/11 at 7:53pm
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post #29 of 199
1/29/08 at 12:22am
Thread Starter 
Quote:
Originally Posted by Febs View Post
Yes, you did. That is exactly what you said. Your thread is titled "ALAC is not lossless."
ALAC isn't lossless. If it were, the file data (and therefore how it sounds) would be identical to the verified, extracted audio data that EAC grabs from a CD.
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post #30 of 199
1/29/08 at 12:23am
Quote:
Originally Posted by IPodPJ View Post
ALAC isn't lossless. If it were, the file data (and therefore how it sounds) would be identical to the verified, extracted audio data that EAC grabs from a CD.
That assumes the input data was identical, see my post above.

If you really want to test it, start with a WAV file, encode the WAV file using ALAC, and then compare the resulting ALAC file to the original WAV file.
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