Differential pulse code modulation (DPCM) is described. First, quantized predictive encoding is motivated but then shown to suffer from amplification of quantization error at the decoder. This problem is avoided by DPCM, which places the quantizer in the prediction loop.
Many information signals, including audio, exhibit significant
redundancy between successive samples.In these situations, it is advantageous to transmit only the difference
between predicted and true versions of the signal:with a “good” predictions, the quantizer input will have variance
less than the original signal, allowing a quantizer with smallerdecision regions and hence higher SNR.
(See
[link] for an example of such a structure.)
Linear Prediction: There are various methods of prediction, but we focus on
forward
linear prediction of order
N , illustrated by
[link] and described by the following equation, where
is a
linear estimate of
based on
N previous versions of
:
It will be convenient to collect the
prediction coefficients into the vector
.
Lossless Predictive Encoding: Consider first the system in
[link] .
The system equations are
In the
z -domain (i.e.,
and
),
We call this transmission system lossless because, from above,
Without quantization, however, the prediction error
takes on a
continuous range of values, and so this scheme is not applicable todigital transmission.
Quantized Predictive Encoding: Quantizing the prediction error in
[link] , we get the
system of
[link] .
Here the equations are
In the
z -domain we find that
Thus the reconstructed output is corrupted by a filtered version of
the quantization error where the filter
is expected to amplify the quantization error; recall that
where the goal of prediction
was to make
.
This problem results from the fact that the quantization noise appearsat the decoder's predictor input but not at the encoder's predictor
input.But we can avoid this...
DPCM: Including quantization in the encoder's prediction loop, we obtain the
system in
[link] , known as
differential pulse code modulation .
System equations are
In the
z -domain we find that
so that
Thus, the reconstructed output is corrupted only by the quantization error.
Another significant advantage to placing the quantizer inside theprediction loop is realized if the predictor made self-adaptive
(in the same spirit as the adaptive quantizers we studied).As illustrated in
[link] , adaptation of the prediction
coefficients can take place simulateously at the encoder anddecoder with no transmission of side-information (e.g.
)!
This is a consequence of the fact that both algorithms have accessto identical signals.
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
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Source:
OpenStax, An introduction to source-coding: quantization, dpcm, transform coding, and sub-band coding. OpenStax CNX. Sep 25, 2009 Download for free at http://cnx.org/content/col11121/1.2
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