Export to flac bit-perfect?

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rema
Posts: 6
Joined: Fri Jul 29, 2016 5:30 am
Operating System: Linux Debian

Export to flac bit-perfect?

Post by rema » Fri Jul 29, 2016 11:50 am

Hello

I have the following behavior which I don't understand:

Source is the wav file onechan.wav.

1.
I convert this file to flac using sox:
sox onechan.wav onechan_sox.flac

2.
I convert the same file to flac using Audacity Dialog "Export Audio..." to onechan_aud.flac

3.
I use flac to convert back to wav
flac -d onechan_sox.flac (results in onechan_sox.wav)
flac -d onechan_aud.flac (results in onechan_aud.wav)

4.
MD5 sums:
$ md5sum onechan.wav
3cecb261e6e6d5bee7f1e4557e04a1a0 onechan.wav
$ md5sum onechan_sox.wav
3cecb261e6e6d5bee7f1e4557e04a1a0 onechan_sox.wav
$ md5sum onechan_aud.wav
161a4222a42ab302b389dd22d225af4d onechan_aud.wav

I cannot understand why the exported flac cannot be converted back in a bit perfect way...

Any hints are very welcome.
I am using Audacity 2.1.2.

Best, René

Gale Andrews
Quality Assurance
Posts: 41761
Joined: Fri Jul 27, 2007 12:02 am
Operating System: Windows 10

Re: Export to flac bit-perfect?

Post by Gale Andrews » Fri Jul 29, 2016 11:57 am

Did you turn off dithering when you exported from Audacity?


Gale
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rema
Posts: 6
Joined: Fri Jul 29, 2016 5:30 am
Operating System: Linux Debian

Re: Export to flac bit-perfect?

Post by rema » Fri Jul 29, 2016 12:33 pm

Gale Andrews wrote:Did you turn off dithering when you exported from Audacity?


Gale
I have now disabled dithering in Preferences|Quality|High-quality conversion.
In addition I have forced 16 bit in the export dialog.

And it works!

Thank you very much.

René

steve
Site Admin
Posts: 80752
Joined: Sat Dec 01, 2007 11:43 am
Operating System: Linux *buntu

Re: Export to flac bit-perfect?

Post by steve » Fri Jul 29, 2016 12:37 pm

Please be aware that in the case of real-world audio work, in which the audio is not only being transcoded but is also being edited and processed, turning off dither will produce lower sound quality and less dynamic range than leaving dither enabled.

For further information, there is an article about "dither" in the Audacity wiki: http://wiki.audacityteam.org/wiki/Dither
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

rema
Posts: 6
Joined: Fri Jul 29, 2016 5:30 am
Operating System: Linux Debian

Re: Export to flac bit-perfect?

Post by rema » Fri Jul 29, 2016 12:49 pm

steve wrote: For further information, there is an article about "dither" in the Audacity wiki: http://wiki.audacityteam.org/wiki/Dither
Thank you for the link!
R.

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