Compressed data have a completely different behaviour concerning defects even if reversible compression procedures will be used. A partly incorrect interpretation of an uncompressed bitmap file will result in artefacts at the corresponding position in the picture. The remaining picture will not be influenced. If the same file will be zipped before, the complete contents is lost at least after the defect's address.

Small defects in video data like MPEG result in visible rectangle patterns ("AC information lost"). If more serious defects arise, the entire frame is concerned. At the worst the decoder has to wait until the next complete frame appears (intra-frame).

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