How FLAC makes audio more compact
A digital recording is a long sequence of numbers, one for each sample of sound. Nearby samples are often similar, so FLAC can predict a sample from the ones around it instead of storing every value in full. It then records the small difference between the prediction and the actual sample. When the prediction is close, that difference takes fewer bits to represent.
The encoder also arranges those differences in a compact form. Crucially, it does not round them off or throw any away: the prediction and the stored differences are enough to reconstruct every original sample exactly.
Compression without a fixed sound penalty
This makes FLAC different from lossy formats, which shrink files by permanently removing audio information. FLAC’s file size depends on how compressible the audio is. Smooth or repetitive passages may yield small differences between predicted and actual samples; dense, irregular sound may be harder to compress. Either way, decoding restores the same digital samples that went in.
That exactness applies to the digital audio data, not to every stage of recording or playback. A microphone, recording setup, or speaker can affect what is captured or heard, but FLAC itself adds no loss when encoding and decoding. The practical tradeoff is straightforward: a file is smaller than uncompressed audio, though usually larger than a lossy version made from the same source.
