Originally Posted by MauneyM
No. You are confusing the term compression with data loss - they are not the same thing.
All codecs use a 'compressed' datastream. However, there is no 'compression' of the audio. The use of the term 'compression' in referring to the audio output from a digital system is incorrect and can cause lots of confusion. It is much more clear to use the descriptive terms 'lossy' and 'lossless'.PCM
(as used on HD media for audio encoding) is not a codec, per se - it represents the pure data stream. This sometimes referred to as 'LPCM' which is redundant, but descriptive.
codec is one where the output signal is not exactly the same as the input signal, i.e., some data was 'lost'. Most lossy codecs currently in use work with 'perceptual encoding'. This means that they attempt to make the output audio as close to the input as possible, but in terms of what the human ear can perceive (not just what the math says). With a lossy codec, increasing the available digital bandwidth will generally reduce the amount of loss, and get you closer to the original signal. The resulting change/loss is NOT compression, as there will not necessarily be any change in the ultimate dynamic range. DD is a lossy codec; DD+ is also lossy, but it uses a higher bandwidth so that it's performance is far better than 640k DD. Thus, DD will not sound as good as (L)PCM, but not because of compression - it's because it's lossy.
codec is one where the output signal will be mathematically identical to the input signal. Think of this as the equivalent to a .ZIP file on your computer; whatever you put in comes out exactly the same - it just takes up less space. Thus, the output of a mathematically lossless codec is indistinguishable from the original source (assuming equal rate and bit depth) and/or (L)PCM. TrueHD and dts-MA are lossless codecs, but the datastream is still compressed.
Just noticed that a few more posts appeared on this thread -- thanks so much for the input, that makes a lot more sense now and I see the potential for confusion between "lossless/lossy" and "compression" in the sense that I used it.
So, if you don't mind humoring me and answering a couple of quick yes/no questions as I try to make sure I really understand the situation:
(Yes/No) 1. A 2.0 PCM signal over toslink is identical in sound quality to running two L/R analog RCA cables (because both are identical lossless streams) and the only difference would be whether I want to use the player's DAC's or the receiver's DAC's
(Yes/No) 2. Assuming I am correct that the answer to Q1 is "yes", this 2-channel PCM signal should theoretically be of higher quality than sending 5.1 DD to my receiver and having it downmix to 2.1 (because DD is a lossy format and the PCM isn't)
(Yes/No) 3. Because I am running a 2.1 set-up, the 2.0 PCM signal (whether via optical or L/R RCA from the analog stereo outs) will theoretically sound JUST AS GOOD as Dolby TrueHD via analog outs (3 cables, one each for L/R and 0.1 channel)? (because the 2.0 PCM signal is lossless, just like the Dolby TrueHD)
(Yes/No) 4. The only difference I would get from running the analog outs would be the separation of an LFE channel, and that my receiver wouldn't be able to do any processing on the audio.
(Yes/No) 5. Considering all this, with my 2.1 setup, there isn't much reason to get an A1 over an A2 because I wouldn't see the benefit of the analog outs. I would get equivalent sound quality sending 2.0 PCM over optical or RCA L/R and letting my Sony ES receiver take case of bass management.
Thanks so much for the feedback!!!