leansdr::s2_scrambling Struct Reference

#include <dvbs2.h>

Public Member Functions
	s2_scrambling (int codenum=0)
uint32_t	lfsr_x (uint32_t X)
uint32_t	lfsr_y (uint32_t Y)

Public Attributes
uint8_t	Rn [131072]

Detailed Description

Definition at line 127 of file dvbs2.h.

Constructor & Destructor Documentation

s2_scrambling()

leansdr::s2_scrambling::s2_scrambling ( int  codenum = 0 )

inline

Definition at line 130 of file dvbs2.h.

References i.

    {
        uint32_t stx = 0x00001, sty = 0x3ffff;
        // x starts at codenum, wraps at index 2^18-1 by design
        for (int i = 0; i < codenum; ++i)
            stx = lfsr_x(stx);
        // First half of sequence is LSB of scrambling angle
        for (int i = 0; i < 131072; ++i)
        {
            int zn = (stx ^ sty) & 1;
            Rn[i] = zn;
            stx = lfsr_x(stx);
            sty = lfsr_y(sty);
        }
        // Second half is MSB
        for (int i = 0; i < 131072; ++i)
        {
            int zn = (stx ^ sty) & 1;
            Rn[i] |= zn << 1;
            stx = lfsr_x(stx);
            sty = lfsr_y(sty);
        }
    }

Member Function Documentation

lfsr_x()

uint32_t leansdr::s2_scrambling::lfsr_x ( uint32_t  X )

inline

Definition at line 153 of file dvbs2.h.

    {
        int bit = ((X >> 7) ^ X) & 1;
        return ((bit << 18) | X) >> 1;
    }

lfsr_y()

uint32_t leansdr::s2_scrambling::lfsr_y ( uint32_t  Y )

inline

Definition at line 158 of file dvbs2.h.

    {
        int bit = ((Y >> 10) ^ (Y >> 7) ^ (Y >> 5) ^ Y) & 1;
        return ((bit << 18) | Y) >> 1;
    }

Member Data Documentation

Rn

uint8_t leansdr::s2_scrambling::Rn[131072]

Definition at line 129 of file dvbs2.h.

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The documentation for this struct was generated from the following file:

• plugins/channelrx/demoddatv/leansdr/dvbs2.h