X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libavcodec%2Flpc.c;h=49e41d8c3447e11f3df320dc24a87e2d5c8f93ec;hb=4fab6627697100ccc3135a13f4d0eb483cbe3227;hp=a8971d3c84726ff0886acd51f9395433eae60658;hpb=81fc8a63c5eed8b151d3035ef6422663ca4cfce4;p=ffmpeg

diff --git a/libavcodec/lpc.c b/libavcodec/lpc.c
index a8971d3c847..49e41d8c344 100644
--- a/libavcodec/lpc.c
+++ b/libavcodec/lpc.c
@@ -1,6 +1,6 @@
 /**
  * LPC utility code
- * Copyright (c) 2006  Justin Ruggles <jruggle@earthlink.net>
+ * Copyright (c) 2006  Justin Ruggles <justin.ruggles@gmail.com>
  *
  * This file is part of FFmpeg.
  *
@@ -21,48 +21,71 @@
 
 #include "libavutil/lls.h"
 #include "dsputil.h"
+
+#define LPC_USE_DOUBLE
 #include "lpc.h"
 
 
 /**
- * Levinson-Durbin recursion.
- * Produces LPC coefficients from autocorrelation data.
+ * Apply Welch window function to audio block
  */
-static void compute_lpc_coefs(const double *autoc, int max_order,
-                              double lpc[][MAX_LPC_ORDER], double *ref)
+static void apply_welch_window(const int32_t *data, int len, double *w_data)
 {
-   int i, j, i2;
-   double r, err, tmp;
-   double lpc_tmp[MAX_LPC_ORDER];
-
-   for(i=0; i<max_order; i++) lpc_tmp[i] = 0;
-   err = autoc[0];
-
-   for(i=0; i<max_order; i++) {
-      r = -autoc[i+1];
-      for(j=0; j<i; j++) {
-          r -= lpc_tmp[j] * autoc[i-j];
-      }
-      r /= err;
-      ref[i] = fabs(r);
-
-      err *= 1.0 - (r * r);
-
-      i2 = (i >> 1);
-      lpc_tmp[i] = r;
-      for(j=0; j<i2; j++) {
-         tmp = lpc_tmp[j];
-         lpc_tmp[j] += r * lpc_tmp[i-1-j];
-         lpc_tmp[i-1-j] += r * tmp;
-      }
-      if(i & 1) {
-          lpc_tmp[j] += lpc_tmp[j] * r;
-      }
-
-      for(j=0; j<=i; j++) {
-          lpc[i][j] = -lpc_tmp[j];
-      }
-   }
+    int i, n2;
+    double w;
+    double c;
+
+    assert(!(len&1)); //the optimization in r11881 does not support odd len
+                      //if someone wants odd len extend the change in r11881
+
+    n2 = (len >> 1);
+    c = 2.0 / (len - 1.0);
+
+    w_data+=n2;
+      data+=n2;
+    for(i=0; i<n2; i++) {
+        w = c - n2 + i;
+        w = 1.0 - (w * w);
+        w_data[-i-1] = data[-i-1] * w;
+        w_data[+i  ] = data[+i  ] * w;
+    }
+}
+
+/**
+ * Calculates autocorrelation data from audio samples
+ * A Welch window function is applied before calculation.
+ */
+void ff_lpc_compute_autocorr(const int32_t *data, int len, int lag,
+                             double *autoc)
+{
+    int i, j;
+    double tmp[len + lag + 1];
+    double *data1= tmp + lag;
+
+    apply_welch_window(data, len, data1);
+
+    for(j=0; j<lag; j++)
+        data1[j-lag]= 0.0;
+    data1[len] = 0.0;
+
+    for(j=0; j<lag; j+=2){
+        double sum0 = 1.0, sum1 = 1.0;
+        for(i=j; i<len; i++){
+            sum0 += data1[i] * data1[i-j];
+            sum1 += data1[i] * data1[i-j-1];
+        }
+        autoc[j  ] = sum0;
+        autoc[j+1] = sum1;
+    }
+
+    if(j==lag){
+        double sum = 1.0;
+        for(i=j-1; i<len; i+=2){
+            sum += data1[i  ] * data1[i-j  ]
+                 + data1[i+1] * data1[i-j+1];
+        }
+        autoc[j] = sum;
+    }
 }
 
 /**
@@ -110,7 +133,7 @@ static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
     /* output quantized coefficients and level shift */
     error=0;
     for(i=0; i<order; i++) {
-        error += lpc_in[i] * (1 << sh);
+        error -= lpc_in[i] * (1 << sh);
         lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
         error -= lpc_out[i];
     }
@@ -133,6 +156,11 @@ static int estimate_best_order(double *ref, int min_order, int max_order)
 
 /**
  * Calculate LPC coefficients for multiple orders
+ *
+ * @param use_lpc LPC method for determining coefficients
+ * 0  = LPC with fixed pre-defined coeffs
+ * 1  = LPC with coeffs determined by Levinson-Durbin recursion
+ * 2+ = LPC with coeffs determined by Cholesky factorization using (use_lpc-1) passes.
  */
 int ff_lpc_calc_coefs(DSPContext *s,
                       const int32_t *samples, int blocksize, int min_order,
@@ -146,15 +174,18 @@ int ff_lpc_calc_coefs(DSPContext *s,
     int i, j, pass;
     int opt_order;
 
-    assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER);
+    assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER && use_lpc > 0);
 
     if(use_lpc == 1){
-        s->flac_compute_autocorr(samples, blocksize, max_order, autoc);
+        s->lpc_compute_autocorr(samples, blocksize, max_order, autoc);
+
+        compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
 
-        compute_lpc_coefs(autoc, max_order, lpc, ref);
+        for(i=0; i<max_order; i++)
+            ref[i] = fabs(lpc[i][i]);
     }else{
         LLSModel m[2];
-        double var[MAX_LPC_ORDER+1], weight;
+        double var[MAX_LPC_ORDER+1], av_uninit(weight);
 
         for(pass=0; pass<use_lpc-1; pass++){
             av_init_lls(&m[pass&1], max_order);
@@ -183,7 +214,7 @@ int ff_lpc_calc_coefs(DSPContext *s,
 
         for(i=0; i<max_order; i++){
             for(j=0; j<max_order; j++)
-                lpc[i][j]= m[(pass-1)&1].coeff[i][j];
+                lpc[i][j]=-m[(pass-1)&1].coeff[i][j];
             ref[i]= sqrt(m[(pass-1)&1].variance[i] / weight) * (blocksize - max_order) / 4000;
         }
         for(i=max_order-1; i>0; i--)