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Old 6th August 2011, 19:11   #20  |  Link
CarlEdman
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Join Date: Jan 2008
Posts: 185
@IanB

Agreed with everything, except for referring to the master as "lossless." The original audio and video signals are in the analogue domain with near-infinite band-width. Any recording, even a digital "master" which doesn't do anything but separately record every pixel for every frame and every audio amplitude for every channel at a high sample rate, is lossy. Both the digital audio and video stream will have both sample rate losses (i.e., sample rate for audio, pixel resolution and frame rate for video) and quantization losses (i.e., the bit-depth of the recorded audio and video).

Now these sampling losses and quantization losses will hopefully have been chosen so that they are outside of the limits of human perception. But in principle, that is all that "lossy" compression does too--throwing away material that is below the level of human perception. All that so-called "lossy" compression does is try to be cleverer about human perception than "lossless" recording which only does simple sampling and quantization.

But there is no principled distinction between the process by which a master is recorded and the later compression stages.

Sorry for the rant. I expect you were aware of that and the distinction between naive so-called "lossless" recording and clever lossy compression is, while only of degree and cleverness of algorithm, is nevertheless useful for some practical purposes. I just get annoyed at people who fetishes losslessness--everything is lossy and we just have to learn to make the best (i.e., least perceptible) of it.
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