Scalar Quantizer Encoder

Encode each input value by associating it with index value of quantization region

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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 zero-based 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:

• Open Model

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 power-of-two 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(N-1)<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(N-1)]. 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 log₂P, where P is the number of boundary points. In most cases, the Binary option is faster than the Linear option.

Tie-breaking 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(N-1)], where i0=0 and i0<i1<i2<...<i(N-1). 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(N-1), 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 fixed-point 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 fixed-point operation. When you clear this parameter, the block wraps the result of its fixed-point operation. For details on saturate and wrap, see overflow mode for fixed-point operations.

Block Characteristics

Data Types	double | fixed point | integer | single
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

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