Use the cleanest available stereo source for a surround upmix. A lossless WAV preserves more detail than an MP3 encoded from the same recording. The AI audio upmixer accepts audio imports and returns separate surround channel stems. Converting an existing MP3 to WAV does not restore information already lost to compression. If your source has obvious noise or compression damage, you can try audio restoration before upmixing, then compare the results before exporting.