dsp.ScalarQuantizerEncoder

Associate input value with index value of quantization region

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Description

The dsp.ScalarQuantizerEncoder object encodes each input value by associating that value with the index value of the quantization region. Then, the object outputs the index of the associated region.

To encode an input value by associating it with an index value of the quantization region:

  1. Create the dsp.ScalarQuantizerEncoder object and set its properties.

  2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?.

Creation

Syntax

sqenc = dsp.ScalarQuantizerEncoder
sqenc = dsp.ScalarQuantizerEncoder(Name,Value)

Description

example

sqenc = dsp.ScalarQuantizerEncoder returns a scalar quantizer encoder System object™, sqenc. This object maps each input value to a quantization region by comparing the input value to the user-specified boundary points.

sqenc = dsp.ScalarQuantizerEncoder(Name,Value) returns a scalar quantizer encoder object, sqenc, with each specified property set to the specified value.

Properties

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Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

Specify how to determine the boundary points and codebook values as 'Property' or 'Input port'.

Specify the quantizer as 'Bounded' or 'Unbounded'.

Specify the boundary points of quantizer regions as a vector. The vector values must be in ascending order. Let [p0 p1 p2 p3 ... pN] denote the boundary points property in the quantizer. If the quantizer is bounded, the object uses this property to specify [p0 p1 p2 p3 ... pN]. If the quantizer is unbounded, the object uses this property to specify [p1 p2 p3 ... p(N-1)] and sets p0 = -Inf and pN = +Inf.

Tunable: Yes

Dependencies

This property applies when you set the BoundaryPointsSource property to Property.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Specify whether to find the appropriate quantizer index using a linear search or a binary search as one of 'Linear' or 'Binary'. The computational cost of the linear search method is of the order P and the computational cost of the binary search method is of the order

log2(P)

where P is the number of boundary points.

Specify whether the input value is assigned to the lower indexed region or higher indexed region when the input value equals boundary point by selecting 'Choose the lower index' or 'Choose the higher index'.

Set this property to true to output the codeword values that correspond to each index value.

Set this property to true to output the quantization error for each input value. The quantization error is the difference between the input value and the quantized output value.

Specify the codebook as a vector of quantized output values that correspond to each region. If the Partitioning property is 'Bounded' and the boundary points vector has length N, you must set this property to a vector of length N-1. If the Partitioning property is 'Unbounded' and the boundary points vector has length N, you must set this property to a vector of length N+1.

Tunable: Yes

Dependencies

This property applies when you set the BoundaryPointsSource property to 'Property' and either the CodewordOutputPort property or the QuantizationErrorOutputPort property is true.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Set this property to true to output the clipping status. The output is a 1 when an input value is outside the range defined by the BoundaryPoints property. When the value is inside the range, the exception output is a 0.

Dependencies

This property applies when you set the Partitioning property to 'Bounded'.

Specify the data type of the index output from the object as: int8, uint8, int16, uint16, int32, uint32.

Fixed-Point Properties

Specify the rounding method.

Specify the overflow action.

Usage

Syntax

index = sqenc(input)
[index] = sqenc(input,bpoints)
[index] = sqenc(input,bpoints,cBook)
[index,codeword] = sqenc(___)
[___,qerr] = sqenc(___)
[___,cStatus] = sqenc(___)

Description

example

index = sqenc(input) returns the index of the quantization region to which the input belongs. The input data, boundary points, codebook values, quantized output values, and the quantization error must have the same data type whenever they are present.

[index] = sqenc(input,bpoints) uses input bpoints as the boundary points when the BoundaryPointsSource property is Input port.

[index] = sqenc(input,bpoints,cBook) uses input bpoints as the boundary points and input cBook as the codebook when the BoundaryPointsSource property is 'Input port' and either the CodewordOutputPort property or the QuantizationErrorOutputPort property is true.

[index,codeword] = sqenc(___) outputs the codeword values that corresponds to each index value when the CodewordOutputPort property is true.

[___,qerr] = sqenc(___) outputs the quantization error qerr for each input value when the QuantizationErrorOutputPort property is true.

[___,cStatus] = sqenc(___) also returns output cStatus as the clipping status output port for each input value when the Partitioning property is 'Bounded' and the ClippingStatusOutputPort property is true. If an input value is outside the range defined by the BoundaryPoints property, cStatus is true. If an input value is inside the range, cStatus is false.

Input Arguments

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Input data, specified as a vector or a matrix. If the input is fixed point, it must be signed fixed point with power-of-two slope and zero bias.

Data Types: single | double | int8 | int16 | int32 | int64 | fi

Boundary points of the quantizer regions, specified as a vector. The vector values must be in ascending order. Let [p0 p1 p2 p3 ... pN] denote the boundary points in the quantizer. If the quantizer is bounded, the object uses this input to specify [p0 p1 p2 p3 ... pN]. If the quantizer is unbounded, the object uses this input to specify [p1 p2 p3 ... p(N-1)] and sets p0 = -Inf and pN = +Inf.

Dependencies

This input applies when you set the BoundaryPointsSource property to Input port.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Codebook, specified as a vector of quantized output values that correspond to each region. If the Partitioning property is 'Bounded' and the boundary points vector has length N, this input must be a vector of length N-1. If the Partitioning property is 'Unbounded' and the boundary points vector has length N, this input must be a vector of length N+1.

Dependencies

This input applies when you set the BoundaryPointsSource property is 'Input port' and either the CodewordOutputPort property or the QuantizationErrorOutputPort property is true.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

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Index of the quantization region to which the input belongs, returned as a vector or a matrix of the same size as the input.

Data Types: int32

Codeword values that correspond to each index value, returned as a vector or a matrix of the same size as the input.

Dependencies

This output is available when the CodewordOutputPort property is set to true.

Data Types: single | double | int8 | int16 | int32 | int64 | fi

Quantization error for each input value, returned as a vector or a matrix of the same size as the input.

Dependencies

This output is available when the QuantizationErrorOutputPort property is set to true.

Data Types: single | double | int8 | int16 | int32 | int64 | fi

Clipping status for each input value, returned as a vector or a matrix. If an input value is outside the range defined by the BoundaryPoints property, cStatus is true. If an input value is inside the range, cStatus is false.

Dependencies

This output is available when the Partitioning property is 'Bounded' and the ClippingStatusOutputPort property is set to true.

Data Types: logical

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

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stepRun System object algorithm
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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Open Live Script

Note: If you are using R2016a or an earlier release, replace each call to the object with the equivalent step syntax. For example, obj(x) becomes step(obj,x).

Quantize the varying fractional inputs between zero and five to the closest integers, and then plot the results.

sqenc = dsp.ScalarQuantizerEncoder;
sqenc.BoundaryPoints = [-.001 .499 1.499 ...
    2.499 3.499 4.499 5.001];
sqenc.CodewordOutputPort = true;
sqenc.Codebook = [0 1 2 3 4 5];
input = (0:0.02:5)';
[index, quantizedValue] = sqenc(input);
plot(1:length(input), [input quantizedValue]);

Algorithms

This object implements the algorithm, inputs, and outputs described on the Scalar Quantizer Encoder block reference page. The object properties correspond to the block parameters.

Extended Capabilities

See Also

Objects

Introduced in R2012a

DSP System Toolbox Documentation

Support