Uniform Encoder
Quantize and encode floatingpoint input into integer output
Library
Quantizers
dspquant2
Description
The Uniform Encoder block performs the following two operations on each floatingpoint sample in the input vector or matrix:
Quantizes the value using the same precision
Encodes the quantized floatingpoint value to an integer value
In the first step, the block quantizes an input value to one of 2^{B} uniformly spaced levels in the range [V, (12^{1B})V], where you specify B in the Bits parameter and you specify V in the Peak parameter. The quantization process rounds both positive and negative inputs downward to the nearest quantization level, with the exception of those that fall exactly on a quantization boundary. The real and imaginary components of complex inputs are quantized independently.
The number of bits, B, can be any integer value between 2 and 32, inclusive. Inputs greater than (12^{1B})V or less than V saturate at those respective values. The real and imaginary components of complex inputs saturate independently.
In the second step, the quantized floatingpoint value is uniquely mapped (encoded) to one
of 2^{B} integer values. When the Output
type is set to Unsigned integer
, the smallest quantized
floatingpoint value, V, is mapped to the integer 0, and the largest
quantized floatingpoint value,
(12^{1B})V, is mapped to the
integer 2^{B}1. Intermediate quantized floatingpoint
values are linearly (uniformly) mapped to the intermediate integers in the range [0,
2^{B}1]. For efficiency, the block automatically
selects an unsigned output data type (uint8
,
uint16
, or uint32
) with the minimum number
of bits equal to or greater than B.
When the Output type is set to Signed
integer
, the smallest quantized floatingpoint value, V, is
mapped to the integer 2^{B1}, and the largest
quantized floatingpoint value,
(12^{1B})V, is mapped to the
integer 2^{B1}1. Intermediate quantized
floatingpoint values are linearly mapped to the intermediate integers in the range
[2^{B1},
2^{B1}1]. The block automatically selects a
signed output data type (int8
,
int16
, or int32
) with the minimum number
of bits equal to or greater than B.
Inputs can be real or complex, double or single precision. The output data types that the block uses are shown in the table below. Note that most of the DSP System Toolbox™ blocks accept only doubleprecision inputs. Use the Simulink^{®} Data Type Conversion block to convert integer data types to double precision. See About Data Types in Simulink (Simulink) for a complete discussion of data types, as well as a list of Simulink blocks capable of reducedprecision operations.
Bits  Unsigned Integer  Signed Integer 










The Uniform Encoder block operations adhere to the definition for uniform encoding specified in ITUT Recommendation G.701.
Examples
See example model ex_uniform_encoder.
In this example, the following parameters are set:
Peak =
2
Bits =
3
Output type =
Unsigned
The following figure illustrates uniform encoding.
The real and complex components of each input (horizontal axis) are independently quantized
to one of 2^{3} distinct levels in the range [2,1.5]
.
These components are then mapped to one of 2^{3} integer values in the
range [0,7]
.
2.0 is mapped to 0 1.5 is mapped to 1 1.0 is mapped to 2 0.5 is mapped to 3 0.0 is mapped to 4 0.5 is mapped to 5 1.0 is mapped to 6 1.5 is mapped to 7
This table shows the results for a few particular inputs.
Input  Quantized Input  Output  Notes 



 


 


 Saturation (real) 


 


 Saturation (imaginary) 


 Saturation (real and imaginary) 
The output data type is automatically set to uint8
, the most
efficient format for this input range.
Parameters
 Peak
The largest input amplitude to be encoded, V. Real or imaginary input values greater than (12^{1B})V or less than V saturate (independently for complex inputs) at those limits.
 Bits
Specify the number of bits, B, needed to represent the integer output. The number of levels at which the block quantizes the floatingpoint input is 2^{B}.
 Output type
The data type of the block's output,
Unsigned integer
orSigned integer
. Unsigned outputs areuint8
,uint16
, oruint32
, while signed outputs areint8
,int16
, orint32
.
References
General Aspects of Digital Transmission Systems: Vocabulary of Digital Transmission and Multiplexing, and Pulse Code Modulation (PCM) Terms, International Telecommunication Union, ITUT Recommendation G.701, March, 1993
Supported Data Types
Port  Supported Data Types 

Input 

Output 

See Also
Data Type Conversion (Simulink)  Simulink 
Quantizer (Simulink)  Simulink 
DSP System Toolbox  
Uniform Decoder  DSP System Toolbox 
udecode  Signal Processing Toolbox 
uencode  Signal Processing Toolbox 