config.c

MPEG-4编解码的实现(包括MPEG4视音频编解码)

 */
static int enter_chn(int cpe, int tag, char position, int common_window, MC_Info *mip)
{
    int nch, cidx=0;
    Ch_Info *cip;

    nch = (cpe == 1) ? 2 : 1;

    switch (position) {
    /* use configuration already in MC_Info, but now common_window is valid */
    case 0:
    cidx = ch_index(mip, cpe, tag);
    if (common_window) {
        mip->ch_info[cidx].widx = cidx; /* window info is left */
        mip->ch_info[cidx+1].widx = cidx;
    } else {
        mip->ch_info[cidx].widx = cidx; /* each has window info */
        mip->ch_info[cidx+1].widx = cidx+1;
    }
    return cidx;

    /* build configuration */
    case 'f':
    if (mip->nfch + nch > FChans) {
/*      CommonWarning("Unanticipated front channel"); */
        return -1;
    }
    if (mip->nfch == 0) {
        /* consider case of center channel */
        if (FCenter) {
        if (cpe) {
            /* has center speaker but center channel missing */
            cidx = 0 + 1;
            mip->nfch = 1 + nch;
        }
        else {
            if (mip->nfsce & 1) {
            /* has center speaker and this is center channel */
            /* odd number of leading SCE's */
            cidx = 0;
            mip->nfch = nch;
            }
            else {
            /* has center speaker but center channel missing */
            /* even number of leading SCE's */
            /* (Note that in implicit congiguration
             * channel to speaker mapping may be wrong
             * for first block while count of SCE's prior
             * to first CPE is being make. However first block
             * is not written so it doesn't matter.
             * Second block will be correct.
             */
            cidx = 0 + 1;
            mip->nfch = 1 + nch;
            }
        }
        }
        else {
        if (cpe) {
            /* no center speaker and center channel missing */
            cidx = 0;
            mip->nfch = nch;
        }
        else {
            /* no center speaker so this is left channel */
            cidx = 0;
            mip->nfch = nch;
        }
        }
    }
    else {
        cidx = mip->nfch;
        mip->nfch += nch;
    }
    break;
    case 's':
    if (mip->nsch + nch > SChans)  {
/*      CommonWarning("Unanticipated side channel"); */
        return -1;
    }
    cidx = FChans + mip->nsch;
    mip->nsch += nch;
    break;
    case 'b':
    if (mip->nbch + nch > BChans) {
/*      CommonWarning("Unanticipated back channel"); */
        return -1;
    }
    cidx = FChans + SChans + mip->nbch;
    mip->nbch += nch;
    break;
    case 'l':
    if (mip->nlch + nch > LChans) {
/*      CommonWarning("Unanticipated LFE channel"); */
        return -1;
    }
    cidx = FChans + SChans + BChans + mip->nlch; /* sdb */
    mip->nlch += nch;
    break;
    default:
/*      CommonExit(1,"2020: Error in channel configuration"); */
        return -1;
    }
    mip->nch += nch;

    if (cpe == 0) {
    /* SCE */
    cip = &mip->ch_info[cidx];
    cip->present = 1;
    cip->tag = tag;
    cip->cpe = 0;
    cip->common_window = common_window;
    cip->widx = cidx;
    mip->nch = cidx + 1;
    }
    else {
        /* CPE */
    /* left */
    cip = &mip->ch_info[cidx];
    cip->present = 1;
    cip->tag = tag;
    cip->cpe = 1;
    cip->common_window = common_window;
    cip->ch_is_left = 1;
    cip->paired_ch = cidx+1;
    /* right */
    cip = &mip->ch_info[cidx+1];
    cip->present = 1;
    cip->tag = tag;
    cip->cpe = 1;
    cip->common_window = common_window;
    cip->ch_is_left = 0;
    cip->paired_ch = cidx;
    if (common_window) {
        mip->ch_info[cidx].widx = cidx; /* window info is left */
        mip->ch_info[cidx+1].widx = cidx;
    }
    else {
        mip->ch_info[cidx].widx = cidx; /* each has window info */
        mip->ch_info[cidx+1].widx = cidx+1;
    }
    mip->nch = cidx + 2;
    }

    return cidx;
}

static char default_position(faacDecHandle hDecoder, MC_Info *mip, int id)
{
    if (mip->nch < FChans)
    {
        if (id == ID_CPE)   /* first CPE */
            hDecoder->first_cpe = 1;
        else if ((hDecoder->frameNum==0) && !hDecoder->first_cpe)
            /* count number of SCE prior to first CPE in first block */
            mip->nfsce++;

        return('f'); /* front */
    }
    else if  (mip->nch < FChans+SChans)
        return('s'); /* side */
    else if  (mip->nch < FChans+SChans+BChans)
        return('b'); /* back */

    return 0;
}

/* retrieve appropriate channel index for the program
 * and decoder configuration
 */
int chn_config(faacDecHandle hDecoder, int id, int tag, int common_window, MC_Info *mip)
{
    int cpe, cidx=0;
    char position;

    /* channel index to position mapping for 5.1 configuration is
     *  0   center
     *  1   left  front
     *  2   right front
     *  3   left surround
     *  4   right surround
     *  5   lfe
     */

    cpe = (id == ID_CPE) ? 1 : 0;

    if (hDecoder->default_config)
    {
        switch (id)
        {
            case ID_SCE:
            case ID_CPE:
                if ((position = default_position(hDecoder, mip, id)) == 0)
                {
/*                  CommonExit(1,"2021: Unanticipated channel"); */
                    return (-1);
                }
                cidx = enter_chn(cpe, tag, position, common_window, mip);
            break;
        }
    }
    else
        cidx = enter_chn(cpe, tag, 0, common_window, mip);


    return cidx;        /* index of chn in mc_info */
}

/*
 * check continuity of configuration from one
 * block to next
 */
void reset_mc_info(faacDecHandle hDecoder, MC_Info *mip)
{
    int i;
    Ch_Info *p;

    /* only reset for implicit configuration */
    if (hDecoder->default_config)
    {
        /* reset channel counts */
        mip->nch = 0;
        mip->nfch = 0;
        mip->nsch = 0;
        mip->nbch = 0;
        mip->nlch = 0;
        mip->ncch = 0;

        if (hDecoder->frameNum == 0)
            /* reset prior to first block scan only! */
            mip->nfsce = 0;

        for (i=0; i<Chans; i++)
        {
            p = &mip->ch_info[i];
            p->present = 0;
            p->cpe = 0;
            p->ch_is_left = 0;
            p->paired_ch = 0;
            p->is_present = 0;
            p->widx = 0;
            p->ncch = 0;
        }
    }
}


int check_mc_info(faacDecHandle hDecoder, MC_Info *mip, int new_config)
{
    int i, nch, err;
    Ch_Info *s, *p;

    nch = mip->nch;
    if (new_config) {
        /* enter valid configuration */
        for (i=0; i<nch; i++) {
            s = &hDecoder->save_mc_info.ch_info[i];
            p = &mip->ch_info[i];
            s->present = p->present;
            s->cpe = p->cpe;
            s->ch_is_left = p->ch_is_left;
            s->paired_ch = p->paired_ch;
        }
    } else {
        /* check this block's configuration */
        err = 0;
        for (i=0; i<nch; i++) {
            s = &hDecoder->save_mc_info.ch_info[i];
            p = &mip->ch_info[i];
            if (s->present != p->present) err=1;
            if (!s->present) continue; /* sdb */
            if (s->cpe != p->cpe) err=1;
            if (s->ch_is_left != p->ch_is_left) err=1;
            if (s->paired_ch != p->paired_ch) err=1;
        }
        if (err) {
            /* CommonExit(1,"Channel configuration inconsistency"); */
            return 0;
        }
    }

    return 1;
}


/* given cpe and tag,
 *  returns channel index of SCE or left chn in CPE
 */
static int ch_index(MC_Info *mip, int cpe, int tag)
{
    int ch;

    for (ch=0; ch<mip->nch; ch++) {

    if (!(mip->ch_info[ch].present))
        continue;

    if ( (mip->ch_info[ch].cpe == cpe) &&
        (mip->ch_info[ch].tag == tag) )
        return ch;
    }

    /* no match, so channel is not in this program
     *  dummy up the ch_info structure so rest of chn will parse
     */
    if (XChans > 0) {
    ch = Chans - XChans;    /* left scratch channel */
    mip->ch_info[ch].cpe = cpe;
    mip->ch_info[ch].ch_is_left = 1;
    mip->ch_info[ch].widx = ch;
    if (cpe) {
        mip->ch_info[ch].paired_ch = ch+1;
        mip->ch_info[ch+1].ch_is_left = 0;
        mip->ch_info[ch+1].paired_ch = ch;
    }
    }
    else {
    ch = -1;        /* error, no scratch space */
    }

    return ch;
}