Topic: Audacity resamples on save?

[Brian Skalinder]

Thanks to SparkE! for bringing this up in another thread:

Please note that Audacity cannot be used for bit perfect editing since it always dithers on saving the file to disk. You can save the same file many times and never get an exact duplicate, due to the dithering. I have not found a way to turn off dithering when saving a file in Audacity. Sometimes dithering is desireable, but it isn't desireable if you are only trying to trim the start and end of a recording. It's only desireable if you have done other things like equalizing, normalizing or compressing the signal. (If someone knows how to turn the dithering on save off in Audacity, I'd love to hear from you.)

Anyone have direct experience with this?  Researched and confirmed there's no way to get around this?

[Lil Kim Jong-Il]

I'm running audacity on a fedora core 2 system. 

I opened audacity, default project rate 16/48.  Imported a 16/48 wav, exported that track to another file name.  cmp verified that the two files were identical.

It was a quick test and far from exhaustive, but proves that audacity (in my installation) does not massage the file when saving.


Edit:

For grins, I installed audacity on a win XP machine and operated on a 16/44 file running the same test.  The saved files are different from the original and from each other. 

Wow, sucks to run audacity on windows I guess.

Edit 2:

Thought about it for a minute then checked the audacity preferences.  The default setting for quality is 44.1k and 32-bit float.  I set the default bit depth to 16-bit.  This solved the problem.  Saved the track twice, tested both saves and the original against each other and of course they are perfect.


It's not just the save function that is affected, it's import as well.  When you set the project quality to 32-float, audacity converts the 16-bit integer value to a float for it's working project values, then back down to a 16-bit integer on export.

So change that setting and you should not have this problem anymore.

[Brian Skalinder]

Good stuff, MGB - thanks for the info!

[setboy]

this means i should Normalize my last show uncut masters again and trash what i have already Normalize right?

Raphael

[Lil Kim Jong-Il]

this means i should Normalize my last show uncut masters again and trash what i have already Normalize right?

Raphael

If you normalized with the working project settings at 16-bit, then yes it may be better to perform normalization again by importing the original 16-bit source into a working project set to 32-float, normalize and then exporting to 16-bit.


If you do this, I'd be really interested to know if you can hear a difference in the quality of the resulting files.

[setboy]

this means i should Normalize my last show uncut masters again and trash what i have already Normalize right?

Raphael

If you normalized with the working project settings at 16-bit, then yes it may be better to perform normalization again by importing the original 16-bit source into a working project set to 32-float, normalize and then exporting to 16-bit.


If you do this, I'd be really interested to know if you can hear a difference in the quality of the resulting files.

i think i may just use Cool edit to do it over BUT i may test 1 or 2 songs to see if i can  hear a difference in quality (if i have time)

Raphael