Hello

I have been taught that you should never use MP3 files in Final Cut, you should always work in Wave or AIFF. Is this true? Is there an audible difference?

MP3 is a compressed lossy format. Wav files are lossless like the raw files of video and contain more details. So better to use the .wav files.

If the file you received is mp3, there is no reason to convert it to WAV or AIFF. If you have a choice of original file format (downloads, recording in an audio recorder, etc.), always go for WAV or AIFF.

I've heard that whatever the file, it should be 48k and not 44k for FCP to be nice.

On a related note, I found out the other day that FCPX does a pretty terrible job of time stretching WAV files. Not talking a lot here, just 1% faster or slower when you just need a tad to make a new edit work late in the game. Had the MP3 preview files from the stock music website in the timeline and they sounded fine at 101%, but when I replaced them with the final WAV files and copied over the retiming properties, I got the "underwater" artifacting sound.

My workaround was to use the free Audacity application to make the tempo change and it worked great. This thread just reminded me of the issue, and how strange that it didn't sound as apparent with the lower-quality MP3 file - just the WAV.

P.S. Doesn't Final Cut automatically transcode MP3 files to WAV on import anyways? There's a folder in the library called "Transcoded Media"