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Because the media uses lossy compression, the uncompressed version of the compressed file still contains artifacts of compression. If you the re-compress the fi
by diafygi 12y ago
Because the media uses lossy compression, the uncompressed version of the compressed file still contains artifacts of compression. If you the re-compress the file, so add even more artifacts.
A good example of this is the guy who re-uploaded the same video to YouTube many times.
http://mashable.com/2010/06/03/youtube-i-am-sitting/ http://mashable.com/2010/06/03/youtube-i-am-sitting/
- KMag 12y agoThe GP's question isn't if current re-encoders are capable of recovering the original compressed data, but rather if it's theoretically possible to write a decompressor that given the parameters to the psyco-acoustic model that's introducing most of the artifacts, is able to produce a compressed file that still has artifacts, but no new artifacts. Yes, it sounds theoretically possible, but it may involve searching a huge search space and may be computationally infeasible.
- nikanj 12y agoHow would you tell that a given artifact is an artifact and not part of the original recording
- KMag 12y agoThe distinction doesn't matter one iota.
- AlyssaRowan 12y agoI'm not sure that it is even theoretically possible, unless the encoder is deterministic. At least some encoders (LAME?) break ties arbitrarily.
- KMag 12y agoThe reversibility depends on the decoder being deterministic, not the encoder.