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Converting to Apple Lossless causes weird analysis in Audacity #236

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
What steps will reproduce the problem?
1. Convert a 24-bit, 48 kHz+ FLAC file to Apple Lossless (bit depth and sample 
rate set to "Same as Original."
2. Analyze the Apple Lossless file in Audacity by going to the Spectrum log(f) 
view.

How about the reproducibility (always, sometimes, rarely, ...)?
Always

What is the expected output? What do you see instead?
For a 24-bit, 48 kHz music FLAC file, the Apple Lossless converted one is 44.1 
kHz and has an inverted polarity.

For a 24-bit, 88.2 kHz music FLAC file, the Apple Lossless converted one is 
44.1 kHz and has an inverted polarity.

For a 24-bit, 96 kHz music FLAC file, the Apple Lossless converted one is 44.1 
kHz and has an inverted polarity.

For a 24-bit, 192 kHz music FLAC file, the Apple Lossless converted one is 44.1 
kHz and has an inverted polarity.

Generating my own 24-bit, 192 kHz 15 kHz sine wave and converting it with XLD, 
Audacity's spectrum analyzer doesn't even show the 15 kHz signal for some 
reason, and instead shows a peak at 3.5 kHz.

In each case, Audirvana Plus detects that the file is the original sample rate, 
but analyzing the file in Audacity says otherwise. Doing a quick A/B between 
the two files, I can't hear a difference.

What version of the product are you using? On what operating system?
I am using the latest version of XLD (Version 20131102 (145.0)) and OS X 10.8.5.

Please provide any additional information below.
See attached files to see the inverted polarity from the original file and a 
very clear cut-off of frequency response.

Also attached is the .txt file that Audacity exports when analyzing the plot 
spectrum.

I'm not sure why this happens, but this is very critical and I think it needs 
to be addressed as soon as possible.

Original issue reported on code.google.com by miceblue...@gmail.com on 17 Mar 2014 at 4:12

Attachments:

GoogleCodeExporter commented 9 years ago 
[deleted comment]
GoogleCodeExporter commented 9 years ago 
Well, converting >16bit, >44.1kHz ALAC files with non-Apple decoder may cause a 
problem due to its bug.

Original comment by tmkkmac on 17 Mar 2014 at 4:16

GoogleCodeExporter commented 9 years ago 
I should also mention that Audacity reads the file as being much longer in 
length than the original file. Consequently, Audacity takes a long time to read 
the file upon opening it.

Original comment by miceblue...@gmail.com on 17 Mar 2014 at 4:17

GoogleCodeExporter commented 9 years ago 
Wow, that was a really, really fast reply!

Is there more information about this bug? This is the first time I've heard 
about it. I usually don't convert my 24-bit, 44.1+ kHz music files, so I just 
found out about this right now.

Original comment by miceblue...@gmail.com on 17 Mar 2014 at 4:19

GoogleCodeExporter commented 9 years ago 
Which version of Audacity are you using?

As far as I've tested with 2.0.3:
 - generating 15kHz, 5-sec tone with Audacity
 - exporting it to 24b/192kHz wav
 - converting it to 24b/192kHz ALAC with XLD
 - opening ALAC again with Audacity
causes no problem.

Anyway please use software which depends on CoreAudio or QuickTime when reading 
ALAC on OSX. Using a 3rd party decoder for ALAC is dangerous.

Original comment by tmkkmac on 17 Mar 2014 at 4:43

GoogleCodeExporter commented 9 years ago 
Interesting, I'm using Audacity version 2.0.5.

Thank you for the tip about Apple Lossless though, I didn't know that.

Original comment by miceblue...@gmail.com on 17 Mar 2014 at 4:48

GoogleCodeExporter commented 9 years ago 
Can you upload your test tone file (before/after convert) which is problematic 
with Audacity?

If you upload to this tracker, very short one (<1sec), please.

Original comment by tmkkmac on 17 Mar 2014 at 5:10

GoogleCodeExporter commented 9 years ago 
Sure thing.

Interestingly, it looks like this version of Audacity doesn't export 24-bit 
audio even though it's set in the settings. Attached are the 16-bit, 192 kHz 
files (original is .flac, converted is .m4a).

Original comment by miceblue...@gmail.com on 17 Mar 2014 at 5:32

Attachments:

GoogleCodeExporter commented 9 years ago 
No problem here.

Your screenshot says ALAC file is imported with 44.1kHz, 32-bit float format. 
My Audacity says 192kHz, 16-bit when reading your ALAC file. So I strongly 
suppose there is something wrong with your Audacity configuration.

Looking into Preferences -> Libraries may help. Isn't FFmpeg importer used? 
FFmpeg is the most infamous example as evil 3rd party ALAC decoder.

Original comment by tmkkmac on 17 Mar 2014 at 5:43

GoogleCodeExporter commented 9 years ago 
It's probably something wrong with my Audacity settings then if yours reads it 
properly.

I just re-installed the FFmpeg (version 0.62) add-on for Audacity and I get the 
same thing.
http://lame1.buanzo.com.ar/

I then installed Audacity 2.0.3 and opened the ALAC file and the same thing 
happened to me as before.

Strange.

Original comment by miceblue...@gmail.com on 17 Mar 2014 at 6:25

GoogleCodeExporter commented 9 years ago 
I mean, don't use ffmpeg with Audacity. And 0.6.2 is too old.

Original comment by tmkkmac on 17 Mar 2014 at 6:30

GoogleCodeExporter commented 9 years ago 
Oooh, you're right! Removing the FFmpeg add-on fixed the problem I was having.

Thank you so much for helping me solve this!

Original comment by miceblue...@gmail.com on 17 Mar 2014 at 7:05

GoogleCodeExporter commented 9 years ago

Original comment by tmkkmac on 17 Mar 2014 at 7:06