Converting MP3 to WAV decodes the lossy-compressed MP3 audio to an uncompressed PCM waveform stored in the WAV container, making the audio compatible with professional recording software and hardware devices that require uncompressed input. MP3 uses MPEG-1 Audio Layer III psychoacoustic lossy compression; WAV stores raw PCM samples at full bit depth (typically 16-bit or 24-bit) and the original sample rate. The decoding step reconstructs the audio waveform from the MP3 bitstream, but it cannot recover the detail that was discarded during the original MP3 encoding — the WAV output is an accurate uncompressed copy of the decoded MP3, not a restoration of the original recording. The file size increases significantly: a 4-minute MP3 at 128 kbps (~3.7 MB) becomes approximately 40 MB as a 16-bit 44.1 kHz WAV. 1converter uses FFmpeg for decoding, preserving sample rate and channel count from the source file.