PCM - A PCM track is an exact replication of the studio master, encoded on disc without compression. The benefit to this is that it maintains the purity of the source without any loss of fidelity that may come from compression. The downside is that an uncompressed audio track takes up a tremendous amount of disc space, which may (especially on single-layer BD25 discs) negatively affect the video quality of the movie. While the Blu-ray format is capable of utilizing PCM audio up to 24-bit resolution, studios may choose to encode at 16-bit resolution instead, depending on the bit depth of the original source or concerns about conserving bandwidth (downsampling a 24-bit master to 16 bits is technically not the same thing as compression). All Blu-ray disc players are required to support PCM audio.