[anamexis]

More just having fun now, but I feel lossless compression implies deterministic decompression, i.e. there is one and only one signal which compresses to a given compressed signal.

Even if you had a signal which compressed to itself, it seems to me that there would likely be other possible signals which would compress to an identical compressed signal.

[yorwba]

Good point, even if compressing and then decompressing does not change anything, you need to know that nothing changed, otherwise you lose information about the compression error.