Operator PARALLELdn

Operator Library: Base

Library: Base

The operator PARALLELdn decreases the parallelism between the input link and the output link.

Following figure shows a parallel down conversion from parallelism 6 at the input down to parallelism 3 at the output.

In VisualApplets, the width of an image line has to be a multiple of the parallelism. As the PARALLELdn operator allows any parallelism at its output it is possible that the width of a image line at the output is not a multiple of the output parallelism. In this case the operator will add dummy pixels to fill up the image line. The value of this dummy pixel is undefined. In VA simulation dummy pixels will be set to zero for better visibility.

The following figure shows in illustration of this dummy pixel insertion. As can be seen, the output parallelism of three cannot map the input line width of eight. Here, one extra dummy pixel is added so that the line width becomes nine.

Note that a parallelism decrease will result in a lower bandwidth of the output link compared to the input link. As the operator cannot buffer data, the reduced output bandwidth is also present at the input and might influence the precedent operators in the image pipeline. Technically, the input of the operator is closed/blocked for some clock cycles at a parallel down conversion. The following figure illustrates the timing of the operator.

The operator requires fewest resources if the input parallelism is an integer multiple of the output parallelism.

I/O Properties

Property Value
Operator Type M
Input Link I, data input
Output Link O, data output

Supported Link Format

Link Parameter Input Link I Output Link O
Bit Width [1, 64]1 as I
Arithmetic {unsigned, signed} as I
Parallelism any <= input parallelism
Kernel Columns any as I
Kernel Rows any as I
Color Format any as I
Color Flavor any as I
Max. Img Width any auto2
Max. Img Height any as I


The range of the input bit width is [1, 64] for unsigned values. For signed inputs, the range is [2, 64]. For unsigned color inputs [3, 63] and for signed color inputs [6, 63].


The output image width must not exceed 2^31 - 1.



Examples of Use

The use of operator PARALLELdn is shown in the following examples: