In the 2.0.4 and 2.0.5 versions, if I import a flac file and immediately export to .wav or .flac again, foobar bit-to-bit comparison plugin detects differences in almost all samples. If I just convert using foobar, no differences in samples.
This never happened in earlier versions. I am on Win7.
What changed? Can anyone reproduce this behavior? or suggest what to do?
It should have done.
Audacity is designed for high quality audio production. If you are doing scientific experiments rather than audio production then you will need to make some tweaks to the preference settings.
For best quality audio production, Audacity works internally in 32 bit float format. If you import a 32 bit float format file into Audacity and then export it again then you should find that it is bit perfect. However, what is the point of importing a file and then exporting it again without editing or processing it in some way?
Processing audio in 32 bit float format is massively more accurate (hence better quality) than 16 bit, but converting from 32 bit float to 16 bit (during export) is not totally lossless. The default settings assume that users will doing something to the audio between importing and exporting, and when doing so there is an overall net benefit in working in 32 bit float format, even though there is a slight (minute) loss when converting back to 16 bit.