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A PCM track is an uncompressed digital format that is 100% bit-for-bit identical to the source fed into it. However, this should hopefully serve to illustrate the basic concept of how a digital file can be compressed without losing important data.) (Note: Please keep in mind that the following examples have been simplified for conceptual purposes, and are not intended to represent the actual mathematical workings of either digital audio encoding or lossless compression, both of which are more complicated than I can explain here. So what would cause a lossless track to not be identical to an uncompressed track? To get to the bottom of this, let's first take a look at the ways in which each audio format is encoded. Theoretically speaking, playing the same movie's soundtrack in both lossless and uncompressed encodings should sound absolutely identical, shouldn't it? Well, yes, except that sometimes there are extenuating circumstances that come into play, and indeed some listeners have tried comparing the soundtracks and claim to hear a difference between them. Examples include Warner's dual-format releases of ' The Departed' and ' Troy: Director's Cut', which feature lossless TrueHD on HD DVD and uncompressed PCM on Blu-ray, or Sony's Blu-ray release of ' Ghost Rider' with both PCM and TrueHD on the same disc. Now that both High-Def formats have been available for over a year, and each has built up a catalog of hundreds of titles, we have several cases where two high-resolution audio tracks (one lossless and one uncompressed) can be directly compared for the same movie. However, some confusion remains as to whether an uncompressed track is actually better than a lossless one. Doing the math, that should mean that a lossless track is also identical to an uncompressed track. In it, I explained that uncompressed PCM audio (as found on many Blu-rays) is an exact replication of the studio master, encoded on disc without compression, and that the lossless audio formats Dolby TrueHD and DTS-HD Master Audio are also bit-for-bit identical to the studio master once decoded. This week: Josh tackles the subjects of whether Uncompressed audio is better than Lossless, and what Dialogue Normalization really does to an audio signal.Ī couple of months ago, I wrote a column called Blu-ray and HD DVD Audio Explained that spelled out the basic functions, features, and differences among the various audio formats available on both High-Def disc types. Editor's Note: As part of his twice-monthly column here at High-Def Digest, from time to time Josh Zyber answers frequently asked questions related to High-Definition and both Blu-ray on HD DVD.