Why do I export the same project twice but get two different files?

I’m using audacity 2.4.2 and I export the file to FLAC, same settings and no metadata.

I checked its CRC-32 with 7-zip and the two files have different results, which means they are not the same.

Hi qyewhxyn

Have you played the two files side by side to make an A-B comparison. Audacity can run with two instances open.

or you can import both files into Audacity, on separate tracks at T=0, and use the Mute buttons (in the Track Control Panels) to switch quickly between them while playing.


The spectrogram and sound of two files look the same, is it the file fingerprinting?

I can’t find the information right now but I vaguely remember that there is some kind of (random?) unique embedded identifier in each file.

The FLAC file actually has an embedded MD5 checksum for just the audio - [u]Checking Your FLACs[/u]

I think that might have been a different format (OGG?) that adds a unique identifier. It’s probably dither… I just exported to FLAC twice with dither disabled) and the files are identical.

FLAC files are either 16-bit or 24-bit.
Audacity works in 32-bit float format, so when exporting to FLAC, each sample value must be rounded in some way to a 16 or 24 bit value.

For audio, normal rounding (rounding up, or rounding down, or rounding to nearest) can have an unfortunate side effect of creating “periodic quantization noise” (unmusical random tones. See: https://en.wikipedia.org/wiki/Quantization_(signal_processing)#Noise).

Audacity, and most other good audio editors, avoid this problem by introducing a little randomization when converting samples to a lower bit format. This randomization is called “dither” (see: https://manual.audacityteam.org/man/dither.html)

This small amount of randomization is sufficient to cause two exports of the same audio track to have different checksums.

Hi DVDdoug
Have you tried export to FLAC twice with dither shaped?