test). Dolby claims its competing AC-3 codec achieves similar transparency at its highest coded bitrate (640 kbit/s). However, in program material available to home consumers (DVD, broadcast, and subscription digital TV), neither AC-3 nor DTS typically run at their highest allowed bitrate. DVD and broadcast (ATSC) HDTV cap AC-3 bitrate at 448 kbit/s. But even at that rate, consumer audio gear already enjoys better audio performance than theatrical (35 mm movie) installations, in which AC-3 is limited to 320kbps. When DTS audio was introduced to the DVD specification, a few studios authored DTS tracks on some DVDs at the full bitrate (1509.75 kbit/s). Most later DVD titles that offered DTS tracks were encoded at 754.5 kbit/s (about half the rate of 1536kbit/s). At this reduced rate, DTS no longer retains audio transparency. This was done to make room for more audio tracks and content to reduce costs of spreading extra material on multiple discs. AC-3 and DTS are sometimes judged by their encoded bitrates. Dolby Digital 5.1 can compress the same data to less, taking up minimal space. Conversely, DTS proponents claim that the extra bits give higher fidelity and more dynamic range, providing a richer and more lifelike sound. But no conclusion can be drawn from their respective bitrates, as each codec relies on different coding tools and syntax to compress audio. In addition to the standard 5.1-channel DTS Surround codec, the company has several other technologies in its product range designed to compete with similar systems from Dolby Labs. Those which conceptually extend DTS (to add more channels and/or more accurate sound reproduction) are implemented as extensions to a core DTS Coherent Acoustics data stream. The core stream is compatible with DTS decoders which do not support the extension(s); the extension(s) provide the additional data required to implement the additional functionality. DTS 70 mm This is a process designed specifically for playback in motion picture theaters equipped with 70mm projection and 6-track surround sound. The 70 mm DTS prints do not have 6-track magnetic striping, so there is no analog backup should the digital sound fail. The time code track on the film is many times wider than the 35mm version, since it can occupy the area formerly taken up by a magnetic track. Theaters with 70 mm DTS frequently install two time code readers for greater reliability. The gradual disappearance of 70 mm as a common exhibition