Uniform Decoder

Decode integer input into floating-point output

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Libraries:
DSP System Toolbox / Quantizers

Description

The Uniform Decoder block performs the inverse operation of the Uniform Encoder block, and reconstructs quantized floating-point values from encoded integer input. The block adheres to the definition for uniform decoding specified in ITU-T Recommendation G.701.

For more information on how the block computes the decoded floating-point output, see Algorithms.

Examples

Decode Integer Data Using Uniform Decoder Block

Decode integer input into floating-point output using the Uniform Decoder block.

Open the ex_uniform_decoder model.

In this example, the input to the block is the uint8 output of a Uniform Encoder block. This block has comparable settings: Peak = 2, Bits = 3, and Output type = Unsigned. These settings ensure that inputs to the Uniform Decoder block do not saturate or wrap. See the example on the Uniform Encoder block reference page for more about these settings.

The block maps the real and complex components of each input independently to one of distinct levels in the range [-2.0,1.5]. The block maps:

• 0 to -2.0

• 1 to -1.5

• 2 to -1.0

• 3 to -0.5

• 4 to 0.0

• 5 to 0.5

• 6 to 1.0

• 7 to 1.5

Ports

Input

Input — Input

vector | matrix

Specify the integer input to be decoded as a vector or a matrix.

The real and imaginary components of complex inputs wrap independently.

Data Types: int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64
Complex Number Support: Yes

Output

Output — Decoded output

vector | matrix

Decoded floating-point output, returned as a vector or a matrix.

For more information on how the block computes the output, see Algorithms.

Data Types: single | double
Complex Number Support: Yes

Parameters

Peak — Largest amplitude in encoded input

1 (default) | nonnegative scalar

Specify the largest amplitude represented in the encoded input as a nonnegative scalar. To correctly decode values encoded with the Uniform Encoder block, set the Peak parameter in both blocks to the same value.

Bits — Number of bits

3 (default) | integer in the range [2, 32]

Specify the number of input bits B used to encode the data. The number of bits B can be any integer value between 2 and 32, inclusive. This value can be less than the total number of bits supplied by the input data type. To correctly decode values encoded with the Uniform Encoder block, set the Bits parameters in both blocks to the same value.

Overflow mode — Overflow mode

Saturate (default) | Wrap

Specify the block behavior when the integer input is outside the range representable by B bits. Out-of-range inputs can either saturate at the extreme value, or wrap back into range.

When you select Saturate, unsigned input values greater than 2^B−1 saturate at 2^B−1 and signed input values greater than 2^B−1−1 or less than −2^B−1 saturate at those limits. The real and imaginary components of complex inputs saturate independently.

When you select Wrap, unsigned input values, u, greater than 2^B−1 wrap back into the range [0, 2^B−1] using mod-2^B arithmetic.

u = mod(u,2^B)

Signed input values, u, greater than 2^B−1−1 or less than −2^B−1 wrap back into that range using mod-2^B arithmetic.

u = (mod(u+2^B/2,2^B)-(2^B/2))	

The real and imaginary components of complex inputs wrap independently.

Output type — Output data type

Double (default) | Single

Specify the precision of the decoded floating-point output as single or double. You can use either level of output precision with any of the six integer input data types.

Block Characteristics

Data Types	integer
Direct Feedthrough	no
Multidimensional Signals	no
Variable-Size Signals	no
Zero-Crossing Detection	no

Algorithms

The Uniform Decoder block first casts the integer input values to floating-point values, and then uniquely maps (decodes) them to one of 2^B uniformly spaced floating-point values in the range [−V, (1−2^1−B)V], where you specify B in the Bits parameter (as an integer between 2 and 32) and V is a floating-point value specified by the Peak parameter. The block maps the smallest input value representable by B bits (0 for an unsigned input data type and −2^B−1 for a signed input data type) to the value −V. It maps the largest input value representable by B bits (2^B−1 for an unsigned input data type and 2^B−1−1 for a signed input data type) to the value (1−2^1−B)V. It linearly maps the intermediate input values to the intermediate values in the range [−V, (1−2^1−B)V].

To correctly decode values encoded by the Uniform Encoder block, the Bits and Peak parameters of the Uniform Decoder block should be set to the same values as the Bits and Peak parameters of the Uniform Encoder block.

References

[1] General Aspects of Digital Transmission Systems: Vocabulary of Digital Transmission and Multiplexing, and Pulse Code Modulation (PCM) Terms, International Telecommunication Union, ITU-T Recommendation G.701, March, 1993

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a