3Why won’t my older DVD player play DTS DVDs?
The DVD DTS flag was not established until Nov 1998. This flag must be
inserted into the DVD’s digital coax or optical output for the receiver to
recognize and decode DTS. Therefore DVD units that are not marked
“DTS ready” will not play DTS even though they have digital outputs.
Can DVD movies contain both DTS and AC-3 audio tracks?
Yes they can. Currently the DVD audio choices are:
·PCM – Producing the conventional analog L/R sound
·Dolby Digital or AC-3 – Compressed 5.1 channel surround sound
·DTS – Compressed 5.1 channel surround sound
How does DTS work?
The DTS and AC-3 encoding formats are generally similar. DTS and AC-
3 can accept digital (PCM) audio with word lengths from 16 to 24 bits.
Both encoders can accept the common 32, 44.1 and 48kHz PCM sam-
pling frequencies, but DTS has 12 more optional frequencies.
The general encoding of the DTS compression system will be explained.
DTS has four blocks used to compress the PCM input audio into a single
bit stream:
PCM audio Time to
6 Channels Frequency Compression
Conversion
6 lines
DTS
Multiplexer Packer Compressed
Bit Stream
Sync
MDCT Time to Frequency Conversion
Each single channel PCM source signal is grouped and allocated to one
of 32 frequency bands for analysis. The process is commonly known as
Modified Discrete Cosine Transformation (MDTC). This frequency band
allocation allows for identification and removal of redundancy among the
channels in the next compression stage.
6
CHANNELS
Coefficients
Coefficients Frequency
Frequency
Compression
Adaptive Predictive Coding (ADPCM)
ADPCM involves smaller support stages to:
·Combine the same sounds found in other channels,
·Remove undetectable audio levels (below human hearing thresholds),
·Remove short interval noises that are swamped by louder sounds
(psycho acoustic masking); and
·Remove transient noises that do not repeat on the same or other
channels.
The support stages include transient, vector and prediction analysis stages
to determine if the sound is short term, increasing or decreasing, and if
the sound will repeat. Removal or the combination of sounds (compres-
sion) is determined by the analysis.