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Original Message
RE: No easy answer
Posted by Tony Lauck on July 8, 2012 at 06:55:10:
Lossy CODECs are not transparent. Neither are the higher rate PCM signals compared with the original analog feed, at least not anywhere near bit rates of 1.5 Mbps. However, if one defines "transparency" in terms of reproducing an already degraded signal, then the correct figure should be based on lossless compression, which compresses almost all audio streams by at least 40%. One can listen to Czech Radio in two channel 16 bit audio at 48 kHz and the data rate of the VBR FLAC encoded stream seldom goes above 900 kbps, even momentarily.
Thus the information loss for AC-3 is really only about 50%, not the 67% you suggest. I view this as an argument against using this compression, since this means there is really no big gain to be had by degrading the quality of audio. It is interesting to know that one of the inventors of peceptual coding does not use it personally.
Lossy compression may make sense for voice and background music. For an audiophile it is death.