'Apocalypto' is presented in two flavors of audio -- an uncompressed PCM 5.1 surround track (48kHz/24-bit/6.9mbps) and Dolby Digital 5.1 (640kbps), both in the film's native Mayan. The PCM track is the definitely the way to go, as the dynamics are clearly inferior on the Dolby track. (Note that for whatever reason, the Mayan Dolby track is not listed on the disc's back packaging, but is accessible via the disc's "Setup" menu. Oddly, it is listed there as English Dolby Digital 5.1, but is actually Mayan.)
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This is from the review on Hi Def Digest