UnpackSFMPEG2()

static void fl::third_party::UnpackSFMPEG2 ( BitStreamInfo * bsi, SideInfoSub * sis, ScaleFactorInfoSub * sfis, int gr, int ch, int modeExt, ScaleFactorJS * sfjs )

static

Definition at line 212 of file scalfact.hpp.

{
    (void)gr;  // Unused parameter - kept for API consistency
 
    int i, sfb, sfcIdx, btIdx, nrIdx;
    int slen[4], nr[4];
    int sfCompress, preFlag, intensityScale;
    
    sfCompress = sis->sfCompress;
    preFlag = 0;
    intensityScale = 0;
 
    /* stereo mode bits (1 = on): bit 1 = mid-side on/off, bit 0 = intensity on/off */
    if (! ((modeExt & 0x01) && (ch == 1)) ) {
        /* in other words: if ((modeExt & 0x01) == 0 || ch == 0) */
        if (sfCompress < 400) {
            /* max slen = floor[(399/16) / 5] = 4 */
            slen[0] = (sfCompress >> 4) / 5;
            slen[1]= (sfCompress >> 4) % 5;
            slen[2]= (sfCompress & 0x0f) >> 2;
            slen[3]= (sfCompress & 0x03);
            sfcIdx = 0;
        } else if (sfCompress < 500) {
            /* max slen = floor[(99/4) / 5] = 4 */
            sfCompress -= 400;
            slen[0] = (sfCompress >> 2) / 5;
            slen[1]= (sfCompress >> 2) % 5;
            slen[2]= (sfCompress & 0x03);
            slen[3]= 0;
            sfcIdx = 1;
        } else {
            /* max slen = floor[11/3] = 3 (sfCompress = 9 bits in MPEG2) */
            sfCompress -= 500;
            slen[0] = sfCompress / 3;
            slen[1] = sfCompress % 3;
            slen[2] = slen[3] = 0;
            if (sis->mixedBlock) {
                /* adjust for long/short mix logic (see comment above in NRTab[] definition) */
                slen[2] = slen[1];  
                slen[1] = slen[0];
            }  
            preFlag = 1;
            sfcIdx = 2;
        }
    } else {    
        /* intensity stereo ch = 1 (right) */
        intensityScale = sfCompress & 0x01;
        sfCompress >>= 1;
        if (sfCompress < 180) {
            /* max slen = floor[35/6] = 5 (from mod 36) */
            slen[0] = (sfCompress / 36);
            slen[1] = (sfCompress % 36) / 6;
            slen[2] = (sfCompress % 36) % 6;
            slen[3] = 0;
            sfcIdx = 3;
        } else if (sfCompress < 244) {
            /* max slen = floor[63/16] = 3 */
            sfCompress -= 180;
            slen[0] = (sfCompress & 0x3f) >> 4;
            slen[1] = (sfCompress & 0x0f) >> 2;
            slen[2] = (sfCompress & 0x03);
            slen[3] = 0;
            sfcIdx = 4;
        } else {
            /* max slen = floor[11/3] = 3 (max sfCompress >> 1 = 511/2 = 255) */
            sfCompress -= 244;
            slen[0] = (sfCompress / 3);
            slen[1] = (sfCompress % 3);
            slen[2] = slen[3] = 0;
            sfcIdx = 5;
        }
    }
    
    /* set index based on block type: (0,1,3) --> 0, (2 non-mixed) --> 1, (2 mixed) ---> 2 */
    btIdx = 0;
    if (sis->blockType == 2) 
        btIdx = (sis->mixedBlock ? 2 : 1);
    for (i = 0; i < 4; i++)
        nr[i] = (int)NRTab[sfcIdx][btIdx][i];
 
    /* save intensity stereo scale factor info */
    if( (modeExt & 0x01) && (ch == 1) ) {
        for (i = 0; i < 4; i++) {
            sfjs->slen[i] = slen[i];
            sfjs->nr[i] = nr[i];
        }
        sfjs->intensityScale = intensityScale;
    }
    sis->preFlag = preFlag;
 
    /* short blocks */
    if(sis->blockType == 2) {
        if(sis->mixedBlock) {
            /* do long block portion */
            for (sfb=0; sfb < 6; sfb++) {
                sfis->l[sfb] = (char)GetBits(bsi, slen[0]);
            }
            sfb = 3;  /* start sfb for short */
            nrIdx = 1;
        } else {      
            /* all short blocks, so start nr, sfb at 0 */
            sfb = 0;
            nrIdx = 0;
        }
 
        /* remaining short blocks, sfb just keeps incrementing */
        for (    ; nrIdx <= 3; nrIdx++) {
            for (i=0; i < nr[nrIdx]; i++, sfb++) {
                sfis->s[sfb][0] = (char)GetBits(bsi, slen[nrIdx]);
                sfis->s[sfb][1] = (char)GetBits(bsi, slen[nrIdx]);
                sfis->s[sfb][2] = (char)GetBits(bsi, slen[nrIdx]);
            }
        }
        /* last sf band not transmitted */
        sfis->s[12][0] = sfis->s[12][1] = sfis->s[12][2] = 0;
    } else {
        /* long blocks */
        sfb = 0;
        for (nrIdx = 0; nrIdx <= 3; nrIdx++) {
            for(i=0; i < nr[nrIdx]; i++, sfb++) {
                sfis->l[sfb] = (char)GetBits(bsi, slen[nrIdx]);
            }
        }
        /* last sf band not transmitted */
        sfis->l[21] = sfis->l[22] = 0;
 
    }
}

References FL_NOEXCEPT, GetBits(), and NRTab.

Referenced by UnpackScaleFactors().

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