6 min read
Does converting audio lose quality? A straight answer for each conversion
Some conversions are mathematically lossless. Some throw data away permanently. Knowing which is which saves your masters.
Conversion anxiety is reasonable, because some operations are perfectly reversible and others quietly destroy information you cannot get back. Here is each common case in production terms.
Lossless conversions
- WAV to AIFF and back: same PCM data, different container. Nothing is lost.
- Splitting a poly WAV into mono files: each channel is copied sample for sample.
- Merging mono files into a poly WAV: interleaving, no processing.
- Renaming, remapping or reordering channels: the samples are untouched.
Lossy conversions
- WAV to MP3 or AAC: a codec discards data it judges inaudible. Irreversible.
- 24 bit to 16 bit: the noise floor rises by roughly 48 dB. Use dither.
- 48 kHz to 44.1 kHz: content above 22 kHz disappears and every sample is recalculated.
- Normalising or applying gain in fixed point: rounding at every sample.
Extracting audio from video
This one surprises people. If the video carries AAC audio, extracting to WAV does not restore what AAC removed. The WAV is a faithful copy of the compressed audio, not an improvement. It is still the right move, because further editing then happens without additional generation loss.
Rules that keep masters intact
- Convert once, from the highest quality source, never from a previous conversion.
- Keep originals archived, work on copies.
- Do lossy encoding last, as a deliverable, never as an intermediate.
- Check sample rate and bit depth before conversion rather than after.
Everything on this site runs in your browser, so conversions happen on your machine and the originals stay where they are.