SOUND FLIPPER GUIDES
Lossless versus lossy audio: what survives?
Understand sample preservation, repeated encoding and why a lossless file made from an MP3 cannot restore discarded detail.
By Singularity Shift Ltd · Updated · Preview guide
Lossless describes a reversible audio encoding
A lossless conversion preserves the supported decoded samples: their values, count, rate and order. It does not necessarily preserve every byte of the original file. Headers, compression choices, timestamps and metadata can change while the audio remains identical.
This distinction matters when checking an archive. Comparing two whole-file checksums is useful for byte-for-byte copies, but two correctly encoded FLAC files can differ as files and still decode to the same PCM. Audio verification needs to compare the samples at their real precision.
Lossy formats make a different tradeoff
MP3, AAC, Opus and Vorbis remove information during encoding. That can make a delivery file much smaller. Whether the difference is audible depends on the recording, encoder settings, listening conditions and listener. A high bitrate is a deliberate quality choice, not a guarantee that every passage is indistinguishable.
Converting an MP3 to AAC is another encoding generation. It cannot recover the discarded information and may introduce further changes. If you have the original WAV or FLAC, make each delivery version from that original.
A measured example, with its limits
Our retained desktop test uses a CC0 speech recording by J and M: 2.5 seconds, 16 kHz, stereo, 16-bit PCM. Its WAV is 160,044 bytes. The verified FLAC output is 89,251 bytes and recovers the same integer samples. The MP3 output is 52,580 bytes, using the high-quality setting allowed at that source rate. Those are actual test files, not estimates or universal compression ratios.
The source is Example of Uptalk Used for Grounding, released under CC0. One short speech clip says little about the size of a drum recording, applause or a full album. It also does not establish perceptual transparency.
Choose a master and a delivery copy
Keep an original recording or a verified lossless master for editing and future exports. Give delivery copies clear names so you do not accidentally use an MP3 as next month's master. After conversion, check duration, the opening and ending, and any quiet or sharp passages important to the recording.
Sound Flipper preserves qualified integer audio through lossless paths. Lossy input is decoded to float WAV before another output is encoded, without a forced reduction to 16-bit. This preserves the decoder's output; it does not undo the original lossy encoding. See WAV to FLAC and how we test.