Application Notes

These functions set and read delay lines of inverse multiscale transformation. The functions receive or return filter low and high frequency component delay line vectors. The functions may be used to shape previous history of each of the components. Installation functions and read functions together ensure that delay lines from each filter are saved and reconstructed.

Delay line data format.

Despite that any delay line formats could be used inside transformations, the functions provide the simplest format of received and returned vectors. Data either transferred to or returned from the delay lines have the same format as the low and high frequency components at the input of the inverse transform functions. Thus, delay line vectors must be made up of a succession of signal prehistory counts in the same time frame as the input components.

Delay line lengths.

The length of the vectors that are transferred to or received by the delay line installation or reading functions is uniquely defined by the filter length and the value of additional filter delay.

The following expression defines the length of the delay line vector of the “low frequency” component filter in terms of the C language (integer division by two is used here for simplicity):

dlyLowLen

= (

lenLow

+

offsLow

- 1) / 2

,

where

lenLow

and

offsLow

are respectively the length and additional delay of the “low frequency” component filter.

The following expression defines the length of the delay line vector of the “high frequency” component filter in terms of the C language:

dlyHighLen

= (

lenHigh

+

offsHigh

- 1) / 2

,

where

lenHigh

and

offsHigh

are respectively the length and additional delay of the “high frequency” component filter.

The

lenLow

,

offsLow

,

lenHigh

, and

offsHigh

parameters are specified by the function

ippsWTInvInit

.