What Is Audio Transcoding?

Step one: decode the source file back to raw PCM audio. Step two: encode the PCM into the target format. The decode step reconstructs the audio from the compressed format. If the source was lossy, some data is already gone and cannot be recovered. The encode step compresses the PCM into the new format. If the target is lossy, more data is discarded. This is why lossy-to-lossy transcoding degrades quality — each step removes information.

Converting MP3 to AAC, or OGG to MP3, re-encodes lossy audio. Each lossy encoding removes more data. The result sounds worse than either format alone from a lossless source. This is called generation loss. Minimize lossy-to-lossy transcoding. When you must do it, use a higher bitrate for the target to compensate. Accept that some quality loss is unavoidable in lossy-to-lossy conversions.

Converting FLAC or WAV to MP3 is the ideal path. The lossy encoder gets perfect input and produces the best possible output for its format. Only one round of lossy compression occurs. This is why you should keep lossless masters: you can always create high-quality lossy versions later. Converting FLAC to MP3 at 320 kbps produces a better result than converting a 128 kbps MP3 to 320 kbps MP3.

Converting WAV to FLAC or ALAC to FLAC is perfectly safe. Both formats are lossless. The decoded audio is identical to the original. No quality loss of any kind. The file size may change depending on the compression efficiency of each format. This type of transcoding is purely a container and compression change — the audio data is preserved perfectly.

Always keep your original files. Convert from the highest quality source available. Avoid chaining lossy conversions — do not convert MP3 to AAC to OGG. If you need multiple lossy formats, create each one from the lossless source. When lossy-to-lossy is unavoidable, use a higher bitrate for the output. Test the result — listen critically to make sure quality is acceptable for your use case.