Originally Posted by William
Then what is your definition of lossy? You can't just base it on what you can/can't hear or if the audio has been altered. If the term is open to interpretation then someone could argue that taking 24bit master and converting to 16bit TrueHD (or LPCM) track would also qualify as lossy since you are taking away from the original. I know you have argued against this.
The term "lossless" should only be properly applied to compression codecs, but it has been hijacked to also describe uncompressed LPCM soundtracks. In truth, you apply the term "lossless" to a compression scheme that gives a byte for byte copy of the encoded source vis. the decoded output. This is opposed to a "lossy" compression scheme which yeilds output that is not a byte for byte copy of the source - i.e. DD+ and DD.
Now, if you like, you can bastardize this definition to say LPCM (as it is on the disk) is "lossless" in that the output when "decoded" is the same as the original LPCM source. The fact that no encoding/decoding takes place makes the term "lossless" silly in this case, but hey, go with what has become standard.
Now whether the source on the disk is an exact copy of the analog sound as it was on the soundstage or not is moot, we are only speaking of a byte for byte copy of the source that was encoded (or not encoded in the case of LPCM) onto the disk.
Notice, none of this applies to the 5.1 Downmixed to 2.0 PCM->PLIIx scenario, because the output from the downmix is most certainly not a byte for byte copy of the 5.1 source. Therefore it fails the definition of "lossless" on the very first step. Besides, as I said - Comparing Pro-Logic from 2.0 to an actuial HD 5.1 audio soundtrack is silly.