一个DVB-C自动搜台的疑问

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DVBC搜台过程中，频点乱序。

背景

Mantis提交了一条问题：DVBC搜台过程中，进度条在前进，频点也在跳动，但是乱序，并非从低到高。
实际情况是：码流机播放《610.750 Network ID 1536.ts》码流，频点设定到482MHz，DVBC搜台过程中，频率从低到高搜，但是搜到482MHz的时候，频率就乱了。

材料

截取部分log信息：

[virtual void CTableScanner::xWorkerThread() 139] CH_SCAN_STATE_BEGIN_FREQ start
[virtual void CTableScanner::xWorkerThread() 145] CH_SCAN_STATE_SCANNING start
xStageBeginFreq:161:: m_isDeleteAll = 1, m_curFreq = 474000000
[virtual void CDtvFreqDetector::xStageBeginFreq() 296] isScanMode = 1, m_curFreq = 474000000, m_curBandwidth = 8000000, tunerId = 0, m_feType = 2, m_modulation = 11, m_symbolrate = 6900000
[bool FrontendLib_SetTuner(UINT32, UINT32, UINT8, RT_FRONTEND_TYPE, RT_MODULATION, RT_SPECTRAL_INVERSION, bool, UINT32, SatelliteInfo *) 156] isScanMode = 1, frequency = 474000000, bandwidth = 8000000, tunerId = 0, feType = 2, modulation = 11, symbolRate = 6900000
[FrontendLib_SetTuner 174] frequency=474000000 bandwidth=8000000 tvSystem=19
[virtual void CDtvFreqDetector::xStageBeginFreq() 298] ret = 0
[virtual void CTableScanner::xWorkerThread() 166] CH_SCAN_STATE_SCANNING end
[virtual void CTableScanner::xWorkerThread() 171] CH_SCAN_STATE_END_FREQ begin
[xUpdateChannelMgr:197] freq=474000000, bSave=1, bUpdateCurChIndex=0, bKeepChannel=0, curFrequency=0, modulation=11
xUpdateChannelMgr 211 RemoveChannel 474000000
[xRemoveChannel:2220]
[bool CDvbTableScanner::xGetNitFreqList(bool) 139] errCode = 1900551, freqCount = 0
[virtual void CTableScanner::xWorkerThread() 139] CH_SCAN_STATE_BEGIN_FREQ start
[virtual void CTableScanner::xWorkerThread() 145] CH_SCAN_STATE_SCANNING start
xStageBeginFreq:161:: m_isDeleteAll = 1, m_curFreq = 482000000
[virtual void CDtvFreqDetector::xStageBeginFreq() 296] isScanMode = 1, m_curFreq = 482000000, m_curBandwidth = 8000000, tunerId = 0, m_feType = 2, m_modulation = 11, m_symbolrate = 6900000
[bool FrontendLib_SetTuner(UINT32, UINT32, UINT8, RT_FRONTEND_TYPE, RT_MODULATION, RT_SPECTRAL_INVERSION, bool, UINT32, SatelliteInfo *) 156] isScanMode = 1, frequency = 482000000, bandwidth = 8000000, tunerId = 0, feType = 2, modulation = 11, symbolRate = 6900000
[FrontendLib_SetTuner 174] frequency=482000000 bandwidth=8000000 tvSystem=19
[virtual void CDtvFreqDetector::xStageBeginFreq() 298] ret = 1
virtual void CDtvFreqDetector::xStageBeginFreq()_304 signal LOCKED !!!!!!!!
[virtual void CDtvFreqDetector::xStageCheckFrontend() 771] m_curFreq = 482000000, m_curBandwidth = 8000000 m_modulation = 11
[virtual void CTableScanner::xWorkerThread() 166] CH_SCAN_STATE_SCANNING end
[virtual void CTableScanner::xWorkerThread() 171] CH_SCAN_STATE_END_FREQ begin
[xUpdateChannelMgr:197] freq=482000000, bSave=1, bUpdateCurChIndex=0, bKeepChannel=0, curFrequency=0, modulation=11
xUpdateChannelMgr 211 RemoveChannel 482000000
[xRemoveChannel:2220]
[bool CDvbTableScanner::xGetNitFreqList(bool) 139] errCode = 0, freqCount = 39
xGetNitFreqList..freq:482750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:458750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:124000000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:466750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:506750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:578750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:386750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:498750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:626750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:650750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:148000000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:714750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:698750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:706750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:762750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:826750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:858750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:642750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:778750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:810750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:834750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:746750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:298750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:602750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:610750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:850750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:140000000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:738750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:530750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:818750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:690750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:164000000, symbolRate:6900000, modulation:9, polarization:0
xGetNitFreqList..freq:842750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:666750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:682750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:156000000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:554750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:490750000, symbolRate:6900000, modulation:11, polarization:0
xGetNitFreqList..freq:132000000, symbolRate:6900000, modulation:11, polarization:0
[Mf_ScanInit 1000] modeEx=0, param=-1, scanMode=7 m_deleteAll=1
[xRemoveChannel:2288] m_chVector.m_size=39
ScanInit….type 2 antennaIndex 0xffffffff typeEx 0 time 304186343
[virtual void CTableScanner::xWorkerThread() 139] CH_SCAN_STATE_BEGIN_FREQ start
[virtual void CTableScanner::xWorkerThread() 145] CH_SCAN_STATE_SCANNING start
xStageBeginFreq:161:: m_isDeleteAll = 1, m_curFreq = 482750000
[virtual void CDtvFreqDetector::xStageBeginFreq() 296] isScanMode = 1, m_curFreq = 482750000, m_curBandwidth = 8000000, tunerId = 0, m_feType = 2, m_modulation = 11, m_symbolrate = 6900000
[bool FrontendLib_SetTuner(UINT32, UINT32, UINT8, RT_FRONTEND_TYPE, RT_MODULATION, RT_SPECTRAL_INVERSION, bool, UINT32, SatelliteInfo *) 156] isScanMode = 1, frequency = 482750000, bandwidth = 8000000, tunerId = 0, feType = 2, modulation = 11, symbolRate = 6900000
[FrontendLib_SetTuner 174] frequency=482750000 bandwidth=8000000 tvSystem=19
[virtual void CDtvFreqDetector::xStageBeginFreq() 298] ret = 1
virtual void CDtvFreqDetector::xStageBeginFreq()_304 signal LOCKED !!!!!!!!
[virtual void CDtvFreqDetector::xStageCheckFrontend() 771] m_curFreq = 482750000, m_curBandwidth = 8000000 m_modulation = 11
[virtual void CTableScanner::xWorkerThread() 166] CH_SCAN_STATE_SCANNING end
[virtual void CTableScanner::xWorkerThread() 171] CH_SCAN_STATE_END_FREQ begin
[xUpdateChannelMgr:197] freq=482750000, bSave=1, bUpdateCurChIndex=0, bKeepChannel=0, curFrequency=0, modulation=11
bool CDvbSiMgr::xUpdateChannelMgr(__UINT32, INT16, bool, bool, bool, __UINT32, RT_MODULATION) 218 count 6
AddChannel:LCN=1,chName=Nederland 1 HD,frequency=482750000
AddChannel:LCN=2,chName=Nederland 2 HD,frequency=482750000
AddChannel:LCN=3,chName=RTL Lounge,frequency=482750000
AddChannel:LCN=4,chName=TVE,frequency=482750000
AddChannel:LCN=5,chName=HZN Barker 1,frequency=482750000
AddChannel:LCN=6,chName=HZN Barker 2,frequency=482750000
bool CDvbSiMgr::xUpdateChannelMgr(__UINT32, INT16, bool, bool, bool, __UINT32, RT_MODULATION) use time 0

使用码流分析工具查看码流：
NIT

代码片段[RTD2831]： 

bool CDvbTableScanner::xGetNitFreqList(bool bDelete)
{
    int freqCount=0;
    SI_DELIVERY_PARAM *pFreqList = NULL;
    ErrCode errCode;
    int startindex=0;
    bool bDelFollow=false;
    bool bAddCurrent=false;
    bool bIncludeExistTP=false;
    RT_FRONTEND_TYPE feType = m_pFreqScanDetector->Mf_GetFrontendType();
    SI *siHandle = (SI*)((IDtvMedia*)m_pTvMedia)->GetDtvFlow()->GetSiHandle();
    if(feType == RT_FRONTEND_DVB_CABLE && !m_bRemoveAll)
    {
        bIncludeExistTP=true;
    }

    errCode = SI_GetFreqList(siHandle, &freqCount, &pFreqList, bIncludeExistTP);
    ALOGD("[%s %d] errCode = %lu, freqCount = %d\n", __func__, __LINE__, errCode, freqCount);

    if (errCode != SI_ERR_OK || freqCount==0 || pFreqList == NULL)
    {
        return FALSE; //如果freqCount为零，就返回了。
    }

    if(feType == RT_FRONTEND_DVB_SATELLITE && m_HomeTp.count!=0)
    {
        bDelete=true;
        if(m_HomeTp.onid!=0)
        {
            bDelete=false;
            for(int i=0;i<freqCount;i++)
            {
                if(pFreqList[i].onid==m_HomeTp.onid)
                {
                    bDelete=true;
                    break;
                }
            }
        }
    }

    if(feType == RT_FRONTEND_DVB_SATELLITE && bDelete && m_pFreqList!=NULL)
    {
        bDelFollow=true;
        bDelete=false;
    }

    if(bDelete || m_pFreqList==NULL)
    {
        xFreeTable();
        
        m_pFreqList = (RT_PHY_CHANNEL *)malloc(sizeof(RT_PHY_CHANNEL) * (freqCount+1));
        if(m_pFreqList == 0)
            return false;
        m_freqListSize = freqCount+1;
        memset(m_pFreqList, 0, sizeof(RT_PHY_CHANNEL)* (m_freqListSize));
        m_isMallocedList=true;
        
        if(feType == RT_FRONTEND_DVB_CABLE)
        {
            bAddCurrent=true;
        }
    }
    else
    {
        RT_PHY_CHANNEL *pFreqList;
        int sizeTmp=m_freqListSize;
        pFreqList = (RT_PHY_CHANNEL *)malloc(sizeof(RT_PHY_CHANNEL)* (sizeTmp+freqCount));
        if(pFreqList==NULL)
        {
            return false;
        }
        memcpy(pFreqList, m_pFreqList, sizeof(RT_PHY_CHANNEL)* (sizeTmp));
        xFreeTable();
        m_pFreqList=pFreqList;
        if(bDelFollow)
            startindex=m_curFreqIndex;
        else
            startindex=sizeTmp;
        m_freqListSize=sizeTmp+freqCount;
        m_isMallocedList=true;
    }

    for (int i = 0; i < freqCount && startindex<m_freqListSize; i++)
    {
        m_pFreqList[startindex].channelNum = startindex;

        m_pFreqList[startindex].frequency = pFreqList[i].frequency;

        switch (pFreqList[startindex].modulation)    // Cable delivery system descriptor, defined in en300468 DVB-SI spec
        {
            case SI_DVB_16_QAM:      // 16QAM,
                m_pFreqList[startindex].modulation = RT_MOD_QAM16;
                break;
            case SI_DVB_32_QAM:      // 32QAM,
                m_pFreqList[startindex].modulation = RT_MOD_QAM32;
                break;
            case SI_DVB_64_QAM:      // 64QAM,
                m_pFreqList[startindex].modulation = RT_MOD_QAM64;
                break;
            case SI_DVB_128_QAM:      // 128QAM,
                m_pFreqList[startindex].modulation = RT_MOD_QAM128;
                break;
                        default:
            case SI_DVB_256_QAM:      // 256QAM,
                m_pFreqList[startindex].modulation = RT_MOD_QAM256;
                break;
        }
        m_pFreqList[startindex].symbolRate = pFreqList[i].symbol_rate;


        if(feType == RT_FRONTEND_DVB_SATELLITE)
        {
            m_pFreqList[startindex].modulation = pFreqList[i].modulation_system == 0 ? RT_MOD_DVB_S : RT_MOD_DVB_S2;
            m_pFreqList[startindex].symbolRate = pFreqList[i].symbol_rate;
        }


        m_pFreqList[startindex].bandwidth = 8000000;
        m_pFreqList[startindex].polarization= pFreqList[i].polarization%2;
        if(bDelete || iSNewTP(m_pFreqList,startindex,&m_pFreqList[startindex]))
        {
            ALOGD("%s..freq:%d, symbolRate:%d, modulation:%d, polarization:%d\n",__FUNCTION__,m_pFreqList[startindex].frequency,m_pFreqList[startindex].symbolRate,
            m_pFreqList[startindex].modulation,m_pFreqList[startindex].polarization);
                startindex++;
        }

        if(bAddCurrent && startindex<m_freqListSize)
        {
            if(m_curFreq/1000000 == m_pFreqList[startindex].frequency/1000000)
            {
                bAddCurrent=false;
            }
        }
    }

    if(bAddCurrent)
    {
        m_pFreqList[startindex].frequency = m_curFreq;
        m_pFreqList[startindex].bandwidth = m_curBandwidth;
        m_pFreqList[startindex].channelNum = m_curChNum;
        m_pFreqList[startindex].modulation = m_curModulation;
        m_pFreqList[startindex].symbolRate = m_curSymbolRate;
        m_pFreqList[startindex].polarization = m_curPolarization;
        startindex++;
    }

    m_freqListSize=startindex;
    return true;
}

bool CDvbTableScanner::iSNewTP(RT_PHY_CHANNEL *src, int size, RT_PHY_CHANNEL *pTp)
{
    if(pTp->frequency == 0)
        return FALSE;
    for(int i=0;i<size;i++)
    {
        if(abs((int)src[i].frequency/100000 - (int)pTp->frequency/100000) < 3)
        {
            if(src[i].symbolRate != pTp->symbolRate)
                continue;

            if(src[i].polarization != pTp->polarization)
                continue;

            if(src[i].modulation != pTp->modulation)
                continue;

            return false;
        }
    }
    return true;
}

结论

可知是NIT的原因，自动搜台的时候（如果没有指定频点）会从频点由低往高搜台，搜到台后，解析NIT时发现有FreqList，就去FreqList里面的频点搜。

参考