RDSDecoder Class Reference

#include <rdsdecoder.h>

Public Member Functions
	RDSDecoder ()
	~RDSDecoder ()
bool	frameSync (bool bit)
unsigned int *	getGroup ()
bool	synced () const

Public Attributes
float	m_qua

Protected Member Functions
unsigned int	calc_syndrome (unsigned long message, unsigned char mlen)
void	enter_sync (unsigned int sync_block_number)
void	enter_no_sync ()

Private Types
enum	{ NO_SYNC, SYNC }

Private Attributes
unsigned long	m_reg
enum RDSDecoder:: { ... }	m_sync
bool	m_presync
unsigned long	m_lastseenOffsetCounter
unsigned long	m_bitCounter
unsigned char	m_lastseenOffset
unsigned int	m_blockBitCounter
unsigned int	m_wrongBlocksCounter
unsigned int	m_blocksCounter
unsigned int	m_groupGoodBlocksCounter
unsigned char	m_blockNumber
bool	m_groupAssemblyStarted
bool	m_goodBlock
unsigned int	m_group [4]

Static Private Attributes
static const unsigned int	offset_pos [5] = {0,1,2,3,2}
static const unsigned int	offset_word [5] = {252,408,360,436,848}
static const unsigned int	syndrome [5] = {383,14,303,663,748}

Detailed Description

Definition at line 22 of file rdsdecoder.h.

Member Enumeration Documentation

anonymous enum

anonymous enum

private

Enumerator
NO_SYNC
SYNC

Definition at line 41 of file rdsdecoder.h.

{ NO_SYNC, SYNC } m_sync;

Constructor & Destructor Documentation

RDSDecoder()

RDSDecoder::RDSDecoder

(

)

Definition at line 28 of file rdsdecoder.cpp.

References m_bitCounter, m_blockBitCounter, m_blockNumber, m_blocksCounter, m_goodBlock, m_group, m_groupAssemblyStarted, m_groupGoodBlocksCounter, m_lastseenOffset, m_lastseenOffsetCounter, m_presync, m_qua, m_reg, m_sync, m_wrongBlocksCounter, and SYNC.

{
    m_reg = 0;
    m_presync = false;
    m_lastseenOffsetCounter = 0;
    m_bitCounter = 0;
    m_lastseenOffset = 0;
    m_blocksCounter        = 0;
    m_blockBitCounter      = 0;
    m_blockNumber          = 0;
    m_groupAssemblyStarted = false;
    m_sync                 = SYNC;
    m_groupGoodBlocksCounter = 0;
    m_wrongBlocksCounter   = 0;
    m_goodBlock            = false;
    m_qua                  = 0.0f;
    memset(m_group, 0, 4*sizeof(int));
}

~RDSDecoder()

RDSDecoder::~RDSDecoder

(

)

Definition at line 47 of file rdsdecoder.cpp.

{
}

Member Function Documentation

calc_syndrome()

unsigned int RDSDecoder::calc_syndrome ( unsigned long  message, unsigned char  mlen  )

protected

see Annex B, page 64 of the standard

Definition at line 240 of file rdsdecoder.cpp.

References i.

Referenced by frameSync().

{
    unsigned long reg = 0;
    unsigned int i;
    const unsigned long poly = 0x5B9;
    const unsigned char plen = 10;

    for (i = mlen; i > 0; i--)
    {
        reg = (reg << 1) | ((message >> (i-1)) & 0x01);
        if (reg & (1 << plen)) reg = reg ^ poly;
    }

    for (i = plen; i > 0; i--)
    {
        reg = reg << 1;
        if (reg & (1<<plen)) {
            reg = reg ^ poly;
        }
    }

    return (reg & ((1<<plen)-1));   // select the bottom plen bits of reg
}

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enter_no_sync()

void RDSDecoder::enter_no_sync ( )

protected

Definition at line 231 of file rdsdecoder.cpp.

References m_presync, m_sync, and NO_SYNC.

Referenced by frameSync().

{
    m_presync = false;
    m_sync = NO_SYNC;
}

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enter_sync()

void RDSDecoder::enter_sync ( unsigned int  sync_block_number )

protected

Definition at line 221 of file rdsdecoder.cpp.

References m_blockBitCounter, m_blockNumber, m_blocksCounter, m_groupAssemblyStarted, m_sync, m_wrongBlocksCounter, and SYNC.

Referenced by frameSync().

{
    m_wrongBlocksCounter   = 0;
    m_blocksCounter        = 0;
    m_blockBitCounter      = 0;
    m_blockNumber          = (sync_block_number + 1) % 4;
    m_groupAssemblyStarted = false;
    m_sync                 = SYNC;
}

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frameSync()

bool RDSDecoder::frameSync

(

bool

bit

)

Definition at line 51 of file rdsdecoder.cpp.

References calc_syndrome(), enter_no_sync(), enter_sync(), m_bitCounter, m_blockBitCounter, m_blockNumber, m_blocksCounter, m_goodBlock, m_group, m_groupAssemblyStarted, m_groupGoodBlocksCounter, m_lastseenOffset, m_lastseenOffsetCounter, m_presync, m_qua, m_reg, m_sync, m_wrongBlocksCounter, NO_SYNC, offset_pos, offset_word, SYNC, and syndrome.

Referenced by BFMDemod::feed().

{
    bool group_ready = false;
    unsigned int reg_syndrome;
    unsigned long bit_distance, block_distance;
    unsigned int block_calculated_crc, block_received_crc, checkword, dataword;

    m_reg = (m_reg<<1) | bit;

    switch (m_sync)
    {
    case NO_SYNC:
        reg_syndrome = calc_syndrome(m_reg,26);

        for (int j = 0; j < 5; j++)
        {
            if (reg_syndrome == syndrome[j])
            {
                if (!m_presync)
                {
                    m_lastseenOffset = j;
                    m_lastseenOffsetCounter = m_bitCounter;
                    m_presync=true;
                }
                else
                {
                    bit_distance = m_bitCounter - m_lastseenOffsetCounter;

                    if (offset_pos[m_lastseenOffset] >= offset_pos[j])
                    {
                        block_distance = offset_pos[j] + 4 - offset_pos[m_lastseenOffset];
                    }
                    else
                    {
                        block_distance = offset_pos[j] - offset_pos[m_lastseenOffset];
                    }

                    if ((block_distance*26)!=bit_distance)
                    {
                        m_presync = false;
                    }
                    else
                    {
                        //qDebug("RDSDecoder::frameSync: Sync State Detected");
                        enter_sync(j);
                    }
                }

                break; //syndrome found, no more cycles
            }
        }
        break;

    case SYNC:
        // wait until 26 bits enter the buffer
        if (m_blockBitCounter < 25)
        {
            m_blockBitCounter++;
        }
        else
        {
            m_goodBlock = false;
            dataword = (m_reg>>10) & 0xffff;
            block_calculated_crc = calc_syndrome(dataword, 16);
            checkword = m_reg & 0x3ff;

            // manage special case of C or C' offset word
            if (m_blockNumber == 2)
            {
                block_received_crc = checkword ^ offset_word[m_blockNumber];

                if (block_received_crc==block_calculated_crc)
                {
                    m_goodBlock = true;
                }
                else
                {
                    block_received_crc=checkword^offset_word[4];

                    if (block_received_crc==block_calculated_crc)
                    {
                        m_goodBlock = true;
                    }
                    else
                    {
                        m_wrongBlocksCounter++;
                        m_goodBlock = false;
                    }
                }
            }
            else
            {
                block_received_crc = checkword ^ offset_word[m_blockNumber];

                if (block_received_crc==block_calculated_crc)
                {
                    m_goodBlock = true;
                }
                else
                {
                    m_wrongBlocksCounter++;
                    m_goodBlock = false;
                }
            }

            //done checking CRC
            if (m_blockNumber == 0 && m_goodBlock)
            {
                m_groupAssemblyStarted = true;
                m_groupGoodBlocksCounter = 1;
            }

            if (m_groupAssemblyStarted)
            {
                if (!m_goodBlock)
                {
                    m_groupAssemblyStarted = false;
                }
                else
                {
                    m_group[m_blockNumber] = dataword;
                    m_groupGoodBlocksCounter++;
                }

                if (m_groupGoodBlocksCounter == 5)
                {
                    group_ready = true; //decode_group(group); pass on to the group parser
                }
            }

            m_blockBitCounter = 0;
            m_blockNumber = (m_blockNumber + 1) % 4;
            m_blocksCounter++;

            // 1187.5 bps / 104 bits = 11.4 groups/sec, or 45.7 blocks/sec
            if (m_blocksCounter == 50)
            {
                if (m_wrongBlocksCounter > 35)
                {
                    /*
                    qDebug() << "RDSDecoder::frameSync: Lost Sync (Got " << m_wrongBlocksCounter
                        << " bad blocks on " << m_blocksCounter
                        << " total)";*/
                    enter_no_sync();
                }
                else
                {
                    /*
                    qDebug() << "RDSDecoder::frameSync: Still Sync-ed (Got " << m_wrongBlocksCounter
                        << " bad blocks on " << m_blocksCounter
                        << " total)";*/
                }

                m_qua = 2.0 * (50 - m_wrongBlocksCounter);
                m_blocksCounter = 0;
                m_wrongBlocksCounter = 0;
            }
        }
        break;
    default:
        break;
    }

    m_bitCounter++;

    return group_ready;
}

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getGroup()

unsigned int* RDSDecoder::getGroup ( )

inline

Definition at line 29 of file rdsdecoder.h.

References m_group.

Referenced by BFMDemod::feed().

{ return m_group; }

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synced()

bool RDSDecoder::synced ( ) const

inline

Definition at line 30 of file rdsdecoder.h.

References m_sync, and SYNC.

{ return m_sync == SYNC; }

Member Data Documentation

m_bitCounter

unsigned long RDSDecoder::m_bitCounter

private

Definition at line 44 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_blockBitCounter

unsigned int RDSDecoder::m_blockBitCounter

private

Definition at line 46 of file rdsdecoder.h.

Referenced by enter_sync(), frameSync(), and RDSDecoder().

m_blockNumber

unsigned char RDSDecoder::m_blockNumber

private

Definition at line 50 of file rdsdecoder.h.

Referenced by enter_sync(), frameSync(), and RDSDecoder().

m_blocksCounter

unsigned int RDSDecoder::m_blocksCounter

private

Definition at line 48 of file rdsdecoder.h.

Referenced by enter_sync(), frameSync(), and RDSDecoder().

m_goodBlock

bool RDSDecoder::m_goodBlock

private

Definition at line 52 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_group

unsigned int RDSDecoder::m_group[4]

private

Definition at line 53 of file rdsdecoder.h.

Referenced by frameSync(), getGroup(), and RDSDecoder().

m_groupAssemblyStarted

bool RDSDecoder::m_groupAssemblyStarted

private

Definition at line 51 of file rdsdecoder.h.

Referenced by enter_sync(), frameSync(), and RDSDecoder().

m_groupGoodBlocksCounter

unsigned int RDSDecoder::m_groupGoodBlocksCounter

private

Definition at line 49 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_lastseenOffset

unsigned char RDSDecoder::m_lastseenOffset

private

Definition at line 45 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_lastseenOffsetCounter

unsigned long RDSDecoder::m_lastseenOffsetCounter

private

Definition at line 43 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_presync

bool RDSDecoder::m_presync

private

Definition at line 42 of file rdsdecoder.h.

Referenced by enter_no_sync(), frameSync(), and RDSDecoder().

m_qua

float RDSDecoder::m_qua

Definition at line 32 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_reg

unsigned long RDSDecoder::m_reg

private

Definition at line 40 of file rdsdecoder.h.

Referenced by frameSync(), and RDSDecoder().

m_sync

enum { ... } RDSDecoder::m_sync

Referenced by enter_no_sync(), enter_sync(), frameSync(), RDSDecoder(), and synced().

m_wrongBlocksCounter

unsigned int RDSDecoder::m_wrongBlocksCounter

private

Definition at line 47 of file rdsdecoder.h.

Referenced by enter_sync(), frameSync(), and RDSDecoder().

offset_pos

const unsigned int RDSDecoder::offset_pos = {0,1,2,3,2}

staticprivate

Definition at line 57 of file rdsdecoder.h.

Referenced by frameSync().

offset_word

const unsigned int RDSDecoder::offset_word = {252,408,360,436,848}

staticprivate

Definition at line 58 of file rdsdecoder.h.

Referenced by frameSync().

syndrome

const unsigned int RDSDecoder::syndrome = {383,14,303,663,748}

staticprivate

Definition at line 59 of file rdsdecoder.h.

Referenced by frameSync().

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The documentation for this class was generated from the following files:

• plugins/channelrx/demodbfm/rdsdecoder.h
• plugins/channelrx/demodbfm/rdsdecoder.cpp