Lossykompressio

Lossykompressio is a data compression method that reduces the size of a file by removing information considered less important for the intended use. The resulting representation is not reversible, meaning some detail is permanently lost. Lossy compression is common for multimedia, including images, audio, and video, where smaller file sizes enable faster transmission and lower storage demands.

Most lossy systems use perceptual coding to decide what data can be discarded without producing noticeable quality loss. A typical encoding pipeline includes a transform stage (for example, a discrete cosine transform in image codecs or a transform such as MDCT in audio codecs), followed by quantization, which reduces precision and discards small coefficients. The final step often uses entropy coding to compress the remaining data efficiently. Because quantization is lossy, the original signal cannot be perfectly reconstructed from the compressed data.

Common examples include JPEG for images, MP3 and AAC for audio, and MPEG-4 or H.264/HEVC for video. Lossy compression can introduce artifacts such as blocky regions, blurring, ringing, or color shifts. The level of distortion depends on the bitrate and the complexity of the content, as well as the codec’s perceptual models.

Evaluation of lossy compression balances bitrate against perceived quality. Objective metrics like PSNR and SSIM are used for images, while perceptual metrics and listening tests assess audio quality. In practice, the choice of codec and bitrate reflects an acceptable trade-off between file size and fidelity within the intended application.