True Audio VS Lossless Audio Checker

You should focus on the frequencies under your Schroeder frequency. REW doesn't show it to you but you can estimate it with the waterfall or calculate it by dividing your room's reverberation time in seconds by the volume of your room in cubic meters, then multiplying the square root of that sum by 2000. You could measure it with TrueRTA as well. Source: almost 3 years ago

Yeah, sure. I use Lossless Audio Checker, which is single threaded but seems to generate fewer false negatives. That is to say it's slow, but doesn't flag genuine lossless files as probable mpegs as much. My biggest beef with LAC is how annoying it is about its log files. It doesn't save them in the folder with the FLACs so I have to manually copy every log file from my Documents folder to the proper location.... Source: about 1 year ago

You can use this to check for artificially inflated bitrate/bitdepth, its fairly accurate, or fbits which can detect exactly how much of the bitdepth is being used. Source: almost 2 years ago

If you have Windows, the Lossless Audio Checker can tell you in about 2 seconds if a WAV or FLAC file has been upsampled/ upscaled/ transcoded. There is also a CLI version for Mac. Source: over 2 years ago

Losslessaudiochecker.com paired with spek.cc when in doubt gets the job done. Source: over 2 years ago

I read about it about a year ago and recently did some tests using https://losslessaudiochecker.com/ to see for myself. And indeed, some songs 320 or FLAC audio files I sourced from deezer were upscaled. Source: over 2 years ago