Chapter 1

DVD Technical Details 103
MPEG-1 and MPEG-2 formats are supported. The variable bit rate is 32 to
912 kbps, with 384 being the normal average rate. MPEG-1 is limited to 384
kbps. Channel combinations are (front/surround) 1/0, 2/0, 2/1, 2/2, 3/0, 3/1,
3/2, and 5/2. The LFE channel is optional with all combinations. The 7.1
channel format adds left-center and right-center channels, but it will probably
be rare for home use.
MPEG-2 surround channels are in an extension stream matrixed onto the
MPEG-1 stereo channels, which makes MPEG-2 audio backwards compatible
with MPEG-1 hardware (an MPEG-1 system will only see the two
stereo channels.) MPEG Layer 3 (MP3) and MPEG-2 AAC (also known as
NBC or unmatrix) are not supported by the DVD-Video standard. MPEG
audio is not used much on DVDs, although some inexpensive DVD recording
software uses MPEG audio, even on NTSC discs, which goes against
the DVD standard and is not supported by all NTSC players.
DTS Digital Surround is an optional multichannel digital audio format,
using lossy compression from PCM at 48 kHz at up to 24 bits. The data rate
is from 64 to 1536 kbps, with typical rates of 754.5 and 1509.25 for 5.1 channels
and 377 or 754 for 2 channels. (The DTS Coherent Acoustics format
supports a variable data rate for lossless compression up to 4096 kbps, but
this isn’t supported on DVDs. DVDs also do not allow DTS sampling rates
other than 48 kHz.) Channel combinations are (front/surround) 1/0, 2/0, 3/0,
2/1, 2/2, and 3/2. The LFE channel is optional with all combinations.
DTS ES supports 6.1 channels in two ways: through a Dolby Surround
EX-compatible matrixed rear-center channel, or through a discrete seventh
channel. DTS also has a 7.1-channel mode (8 discrete channels), but no
DVDs have used it yet. The seven-channel and eight-channel modes
require a new decoder.
The DVD standard includes an audio stream format reserved for DTS,
but many older players ignore it. The DTS format used on DVDs is different
from the one used in theaters (Audio Processing Technology’s apt-X, which
is an ADPCM coder, not a psycho-acoustic coder). All DVD players can play
DTS audio CDs, because the standard PCM stream holds the DTS code.
See “What’s the Deal with DTS and DVDs?” in Chapter 1 for general DTS
information. For more info, visit www.dtstech.com and read Adam Barratt’s
article at home.clearnet.nz/pages/adbarr/page1.html.
SDDS is an optional multichannel (5.1 or 7.1) digital audio format, compressed
from PCM at 48 kHz. The data rate can go up to 1280 kbps. SDDS
is a theatrical film soundtrack format based on the Adaptive Transform
Acoustic Coding (ATRAC) compression format also used by Minidisc. Sony
has not announced any plans to support SDDS on DVD.
THX (Tomlinson Holman Experiment) is not an audio format. It’s a certification
and quality control program that applies to sound systems and