Scalar Quantizer Encoder
Encode each input value by associating it with index value of quantization region
Libraries:
DSP System Toolbox /
Quantizers
Description
The Scalar Quantizer Encoder block maps each input value to a quantization region by comparing the input value to the quantizer boundary points defined in the Boundary points parameter. The block outputs the zerobased index of the associated region.
Examples
Add a Scalar Quantizer
In this topic, you add scalar quantizer encoders and decoders to quantize the residual signal E and the reflection coefficients K:
Ports
Input
U — Input data values
vector  matrix
Specify the input data values as a vector or a matrix.
The input data, boundary points, codebook values, quantized output values, and the quantization error must have the same data type whenever they are present.
If the input is fixed point, it must be a signed integer or a signed fixed point value with a poweroftwo slope and zero bias.
Data Types: single
 double
 int8
 int16
 int32
 fixed point
B — Boundary points
vector
Specify the boundary points as a vector of length N. You must enter the boundary points in ascending order.
The input data, boundary points, codebook values, quantized output values, and the quantization error must have the same data type whenever they are present.
Dependencies
To enable this port, select Input port
from the Source of quantizer parameters
list.
Data Types: single
 double
 int8
 int16
 int32
 fixed point
C — Codebook values
vector
Enter a vector of quantized output values that correspond to each index value. The length of the codebook vector must be N−1, where N is the length of the boundary points vector.
The input data, boundary points, codebook values, quantized output values, and the quantization error must have the same data type whenever they are present.
Dependencies
To enable this port, select Input port
from the Source of quantizer parameters list
and you select either the Output codeword or
Output quantization error check box.
Data Types: single
 double
 int8
 int16
 int32
 fixed point
Output
I — Index values
vector  matrix
Index values, returned as a vector or a matrix of the same size as the input data.
The data type of this port depends on the setting of the Index output data type parameter.
Data Types: int8
 int16
 int32
 uint8
 uint16
 uint32
Q(U) — Quantized output values
vector  matrix
Quantized output values, returned as a vector or a matrix of the same size as the input data. These are the codeword values that correspond to each index value.
The input data, boundary points, codebook values, quantized output values, and the quantization error must have the same data type whenever they are present.
Dependencies
To enable this port, select the Output codeword parameter.
Data Types: single
 double
 int8
 int16
 int32
 fixed point
Err — Quantization error
vector  matrix
Quantization error, returned as a vector or a matrix of the same size as the input data. The quantization error is the difference between the input value and the quantized output value.
The input data, boundary points, codebook values, quantized output values, and the quantization error must have the same data type whenever they are present.
Dependencies
To enable this port, select the Output quantization error parameter.
Data Types: single
 double
 int8
 int16
 int32
 fixed point
S — Clipping status
vector  matrix
Clipping status values, returned as a vector or a matrix of boolean values of the same size as the input data. Any time an input value is outside the range defined by the Boundary points parameter, the block outputs a 1 at the S port. When the value is inside the range, the blocks outputs a 0.
Dependencies
To enable this port, select the Output clipping status check box.
Data Types: Boolean
Parameters
Main Tab
Source of quantizer parameters — Source of quantizer parameters
Specify via dialog
(default)  Input port
Specify the source of quantizer parameters as one of these:
Specify via dialog
–– Enter the boundary points and the codebook values using the parameters in the dialog box.Input port
–– Specify the parameters using the block input ports. Input the boundary points and the codebook values using ports B and C, respectively.
Partitioning — Partitioning method
Bounded
(default)  Unbounded
Specify one of these partitioning methods to interpret the boundary points you enter:
Bounded
–– Select this option to create a bounded quantizer.For example, when you enter these boundary points:
[0 0.5 3.7 5.8 6.0 11]
The block assigns any input values between 0 and 0.5 to index 0, input values between 0.5 and 3.7 to index 1, and so on. The block assigns any values that are less than 0 to index 0, the lowest index value. The block assigns any values that are greater than 11 to index 4, the highest index value.
Unbounded
–– Select this option to create an unbounded quantizer.For example, when you enter these boundary points:
[0 0.5 3.7 5.8 6.0 11]
The block assigns any input values between 0 and 0.5 to index 1, input values between 0.5 and 3.7 to index 2, and so on. The block assigns any input values less than 0 to index 0 and any values greater than 11 to index 6.
Boundary points — Boundary points
[1:10]
(default)  vector
Enter a vector of values in ascending order that represent the boundary points of the quantizer regions. These values are used to break up the set of input numbers into regions. Each region is specified by an index number.
Let N be the number of quantization regions. When
the codebook is defined as [c1 c2 c3 ... cN]
, and the
Boundary points parameter is defined as
[p0 p1 p2 p3 ... pN]
, then
p0<c1<p1<c2 ... p(N1)<cN<pN
for a
regular quantizer. When your quantizer is bounded, from the
Partitioning list, select
Bounded
. You need to specify
N+1 boundary points, or [p0 p1 p2 p3 ...
pN]
. When your quantizer is unbounded, from the
Partitioning list, select
Unbounded
. You need to specify
N−1 boundary points, or[p1 p2 p3 ...
p(N1)]
. The block sets p0
equal to
−inf
and pN
equal to
inf
.
Tunable: Yes
Dependencies
To enable this parameter, select Specify via
dialog
from the Source of quantizer
parameters list.
Searching method — Searching method
Linear
(default)  Binary
Specify the searching method the block uses to determine the region in which the input value is located (quantizer index):
Linear
–– The block compares the input value to the first region defined by the first two boundary points. When the input value does not fall within this region, the block then compares the input value to the next region. This process continues until the input value is determined to be within a region and is associated with the appropriate index value. The computational cost of this process is of the order P, where P is the number of boundary points.Binary
–– The block compares the input value to the middle value of the boundary points vector. When the input value is larger than this boundary point, the block discards the boundary points that are lower than this middle value. The block then compares the input value to the middle boundary point of the new range, defined by the remaining boundary points. This process continues until the input value is associated with the appropriate index value. The computational cost of this process is of the order log_{2}P, where P is the number of boundary points. In most cases, theBinary
option is faster than theLinear
option.
Tiebreaking rule — Action when input value is same as boundary point
Choose the lower
index
(default)  Choose the higher index
Specify one of these actions to take when the input value is the same as the boundary point. This parameter determines the region to which the value is assigned.
Choose the lower index
–– The block assigns the input value to the lower indexed region.Choose the higher index
–– The block assigns the input value to the higher indexed region.
Output codeword — Output codeword
off
(default)  on
Select this check box to output the codeword values that correspond to each index value at port Q(U).
Output quantization error — Output quantization error
off
(default)  on
Select this check box to output the quantization error for each input value at port Err. The quantization error is the difference between the input value and the quantized output value.
Codebook — Quantized output values
[1.5:9.5]
(default)  vector
Enter a vector of quantized output values that correspond to each index value.
If you set the Partitioning parameter to
Bounded
and your boundary points vector
has a length of N, then you must specify a codebook
of length N−1. If you set the
Partitioning parameter to
Unbounded
and your boundary points vector
has a length of N, then you must specify a codebook
of length N+1.
Tunable: Yes
Dependencies
To enable this parameter, select Specify via dialog
from the
Source of quantizer parameters list and
select either the Output codeword or
Output quantization error check box.
Output clipping status — Output clipping status
off
(default)  on
Specify the output clipping status on the port S. Any time an input value is outside the range defined by the Boundary points parameter, the block outputs a 1 at this port. When the value is inside the range, the block outputs a 0.
Dependencies
To enable this parameter, set the
Partitioning parameter to
Bounded
.
Action for out of range input — Action for out of range input
Clip
 Clip and warn
 Error
Specify one of these actions the block must take when an input value is outside the range defined by the Boundary points parameter:
Clip
Clip and warn
Error
Suppose the boundary points for a bounded quantizer are defined as
[p0 p1 p2 p3 ... pN]
and the possible index
values are defined as [i0 i1 i2 ... i(N1)]
, where
i0=0
and
i0<i1<i2<...<i(N1)
. When you want
any input value less than p0
to be assigned to index
value i0
and any input values greater than
pN
to be assigned to index value
i(N1)
, select Clip
. When you
want to be warned when clipping occurs, select Clip and
warn
. When you want the simulation to stop and the
block to display an error when the index values are out of range, select
Error
.
Dependencies
To enable this parameter, set the
Partitioning parameter to
Bounded
.
Index output data type — Index output data type
int32
(default)  int8
 uint8
 int16
 uint16
 int32
 uint32
 Inherit via back propagation
Specify the data type of the index output from the block at port I as one of these:
int8
uint8
int16
uint16
int32
uint32
Inherit via back propagation
Data Types Tab
Rounding mode — Rounding mode
Floor
(default)  Ceiling
 Convergent
 Nearest
 Round
 Simplest
 Zero
Specify the rounding mode for fixedpoint operations as one of the following:
Floor
Ceiling
Convergent
Nearest
Round
Simplest
Zero
For more details, see rounding mode.
Saturate on integer overflow — Saturate on integer overflow
off
(default)  on
When you select this parameter, the block saturates the result of its
fixedpoint operation. When you clear this parameter, the block wraps
the result of its fixedpoint operation. For details on
saturate
and wrap
, see overflow
mode for fixedpoint operations.
Block Characteristics
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 

References
[1] Gersho, A. and R. Gray. Vector Quantization and Signal Compression. Boston: Kluwer Academic Publishers, 1992.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
Version History
Introduced before R2006a
See Also
Quantizer (Simulink)  Scalar Quantizer Decoder  Uniform Encoder  Uniform Decoder
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