Answer
Dolby Digital and DTS are similar in that they are both digital lossy audio coding technologies, which means they use “perceptual” data reduction techniques that are based on the characteristics of human hearing to mask the process, thereby preserving high fidelity sound. This is necessary in order to fit the typical 5.1-channel bitstream into a given storage space or transmission bandwidth. Beyond those basic similarities, the two formats are very different.
Venues
Dolby Digital and DTS were both initially designed to improve the sonic performance of commercial theaters, without forcing those houses to uproot all of their existing equipment. Originally, the formats were either printed on the film itself or supplied through a separate disc. Today, most of the audio and video on commercial releases is on a hard drive when film reels are not used. DVD, Blu-ray and digital television broadcasts all utilize one format or both to deliver high-quality audio to digital home-theater environments.
Format Compression
Both Dolby Digital and DTS at their core are "lossy" compressed formats. In order to fit the large amount of data on a r-inch DVD or Blu-ray disc, compression is needed. With DVD and digital television broadcasting, Dolby Digital eliminates a large percentage of the original recording, keeping the essential amount to maintain good fidelity. DTS does the same, but less so and playing back at higher bit rates. This technique often results in a sound with a little more sparkle and rumble than a comparable Dolby Digital recording, but many times the two are virtually indistinguishable. Dolby Digital and DTS on DVD offer an average bit rate of 448 and 1,536 kilobits per second respectively.
Blu-ray Playback
Both Dolby Digital and DTS evolved to offer new lossless formats with Dolby TrueHD and DTS Master Audio. Both are virtually identical to the master recording, and so are practically identical to each other. The difference is the flexibility in playback. DTS utilizes a unique core system, whereby the DTS track is encoded with two streams. The DTS high-resolution stream is added to the core or residual stream to create the full, lossless track. The core stream is sent to the HDMI, optical digital and coaxial outputs when used with legacy systems not supporting lossless codecs. The other portion is sent to the HDMI output as well. Combined, the two streams form the full DTS-MA format. Dolby TrueHD was not common on older Blu-ray players, and unlike with DVD, Dolby's format is the optional one. As with DTS-MA, Dolby TrueHD offers uncompressed 24 bit, 192 kilohertz audio over eight playback channels. Dolby TrueHD offers a standard Dolby Digital track selected at the playback menu to facilitate Blu-ray use with older audio systems.
PCM Alternatives
All digital formats are built upon pulse code modulation. Dolby Digital and DTS are built upon this standard, each applying proprietary compression schemes. Each format may be decoded either in the player or receiver. In the former case, audio is sent over raw PCM via HDMI or a series of six to eight separate RCA cables. The sound is identical in either case. Note that PCM playback is possible on any legacy or modern home-theater receiver featuring a six or eight channel external RCA input cluster, and does not require internal DTS Master Audio or Dolby TrueHD decoding.
References
DTS: Resource Center
HiFi Writer: Dolby Digital vs DTS: Which is Better?
Dolby: Dolby TrueHD
No comments:
Post a Comment