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