Revision 1be0fc29 libavcodec/lpc.h

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libavcodec/lpc.h
45 45
                      int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
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                      int omethod, int max_shift, int zero_shift);
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#ifdef LPC_USE_DOUBLE
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#define LPC_type double
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#else
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#define LPC_type float
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#endif
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/**
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 * Levinson-Durbin recursion.
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 * Produces LPC coefficients from autocorrelation data.
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 */
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static inline int compute_lpc_coefs(const LPC_type *autoc, int max_order,
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                                    LPC_type *lpc, int lpc_stride, int fail,
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                                    int normalize)
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{
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    int i, j;
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    LPC_type err;
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    LPC_type *lpc_last = lpc;
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    if (normalize)
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        err = *autoc++;
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    if (fail && (autoc[max_order - 1] == 0 || err <= 0))
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        return -1;
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    for(i=0; i<max_order; i++) {
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        LPC_type r = -autoc[i];
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        if (normalize) {
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            for(j=0; j<i; j++)
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                r -= lpc_last[j] * autoc[i-j-1];
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            r /= err;
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            err *= 1.0 - (r * r);
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        }
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        lpc[i] = r;
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        for(j=0; j < (i+1)>>1; j++) {
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            LPC_type f = lpc_last[    j];
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            LPC_type b = lpc_last[i-1-j];
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            lpc[    j] = f + r * b;
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            lpc[i-1-j] = b + r * f;
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        }
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        if (fail && err < 0)
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            return -1;
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        lpc_last = lpc;
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        lpc += lpc_stride;
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    }
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    return 0;
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}
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#endif /* AVCODEC_LPC_H */

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