Learn in the textbookData Compression Methods and Characteristics
DefinitionLossy compression (非可逆圧縮) is a compression method that removes information people barely notice to cut the data size sharply, so decompression cannot fully restore the original.
ExplanationThe removed information never comes back, but that is exactly what allows such large reductions. It suits photos, audio, and video, where a slight loss of quality is hard to spot, and typical formats are JPEG for photos, MP3 for audio, and MPEG for video.
AnalogyIt is like retelling a long story in a few lines. The main points get across, but the listener cannot recover the original wording.
Memory hookSpilled water cannot be gathered back into the bucket, and the details you cut cannot be put back either.