From 8992cb1d0d07edc33d274f6d7924ecdf6f83d994 Mon Sep 17 00:00:00 2001
From: Tim Redfern <tim@eclectronics.org>
Date: Thu, 5 Sep 2013 17:57:22 +0100
Subject: making act segmenter

---
 ffmpeg/libavcodec/lpc.c | 287 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 287 insertions(+)
 create mode 100644 ffmpeg/libavcodec/lpc.c

(limited to 'ffmpeg/libavcodec/lpc.c')

diff --git a/ffmpeg/libavcodec/lpc.c b/ffmpeg/libavcodec/lpc.c
new file mode 100644
index 0000000..4149135
--- /dev/null
+++ b/ffmpeg/libavcodec/lpc.c
@@ -0,0 +1,287 @@
+/*
+ * LPC utility code
+ * Copyright (c) 2006  Justin Ruggles <justin.ruggles@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/common.h"
+#include "libavutil/lls.h"
+
+#define LPC_USE_DOUBLE
+#include "lpc.h"
+#include "libavutil/avassert.h"
+
+
+/**
+ * Apply Welch window function to audio block
+ */
+static void lpc_apply_welch_window_c(const int32_t *data, int len,
+                                     double *w_data)
+{
+    int i, n2;
+    double w;
+    double c;
+
+    /* The optimization in commit fa4ed8c does not support odd len.
+     * If someone wants odd len extend that change. */
+    av_assert2(!(len & 1));
+
+    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;
+    }
+}
+
+/**
+ * Calculate autocorrelation data from audio samples
+ * A Welch window function is applied before calculation.
+ */
+static void lpc_compute_autocorr_c(const double *data, int len, int lag,
+                                   double *autoc)
+{
+    int i, j;
+
+    for(j=0; j<lag; j+=2){
+        double sum0 = 1.0, sum1 = 1.0;
+        for(i=j; i<len; i++){
+            sum0 += data[i] * data[i-j];
+            sum1 += data[i] * data[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 += data[i  ] * data[i-j  ]
+                 + data[i+1] * data[i-j+1];
+        }
+        autoc[j] = sum;
+    }
+}
+
+/**
+ * Quantize LPC coefficients
+ */
+static void quantize_lpc_coefs(double *lpc_in, int order, int precision,
+                               int32_t *lpc_out, int *shift, int max_shift, int zero_shift)
+{
+    int i;
+    double cmax, error;
+    int32_t qmax;
+    int sh;
+
+    /* define maximum levels */
+    qmax = (1 << (precision - 1)) - 1;
+
+    /* find maximum coefficient value */
+    cmax = 0.0;
+    for(i=0; i<order; i++) {
+        cmax= FFMAX(cmax, fabs(lpc_in[i]));
+    }
+
+    /* if maximum value quantizes to zero, return all zeros */
+    if(cmax * (1 << max_shift) < 1.0) {
+        *shift = zero_shift;
+        memset(lpc_out, 0, sizeof(int32_t) * order);
+        return;
+    }
+
+    /* calculate level shift which scales max coeff to available bits */
+    sh = max_shift;
+    while((cmax * (1 << sh) > qmax) && (sh > 0)) {
+        sh--;
+    }
+
+    /* since negative shift values are unsupported in decoder, scale down
+       coefficients instead */
+    if(sh == 0 && cmax > qmax) {
+        double scale = ((double)qmax) / cmax;
+        for(i=0; i<order; i++) {
+            lpc_in[i] *= scale;
+        }
+    }
+
+    /* output quantized coefficients and level shift */
+    error=0;
+    for(i=0; i<order; i++) {
+        error -= lpc_in[i] * (1 << sh);
+        lpc_out[i] = av_clip(lrintf(error), -qmax, qmax);
+        error -= lpc_out[i];
+    }
+    *shift = sh;
+}
+
+static int estimate_best_order(double *ref, int min_order, int max_order)
+{
+    int i, est;
+
+    est = min_order;
+    for(i=max_order-1; i>=min_order-1; i--) {
+        if(ref[i] > 0.10) {
+            est = i+1;
+            break;
+        }
+    }
+    return est;
+}
+
+int ff_lpc_calc_ref_coefs(LPCContext *s,
+                          const int32_t *samples, int order, double *ref)
+{
+    double autoc[MAX_LPC_ORDER + 1];
+
+    s->lpc_apply_welch_window(samples, s->blocksize, s->windowed_samples);
+    s->lpc_compute_autocorr(s->windowed_samples, s->blocksize, order, autoc);
+    compute_ref_coefs(autoc, order, ref, NULL);
+
+    return order;
+}
+
+/**
+ * Calculate LPC coefficients for multiple orders
+ *
+ * @param lpc_type LPC method for determining coefficients,
+ *                 see #FFLPCType for details
+ */
+int ff_lpc_calc_coefs(LPCContext *s,
+                      const int32_t *samples, int blocksize, int min_order,
+                      int max_order, int precision,
+                      int32_t coefs[][MAX_LPC_ORDER], int *shift,
+                      enum FFLPCType lpc_type, int lpc_passes,
+                      int omethod, int max_shift, int zero_shift)
+{
+    double autoc[MAX_LPC_ORDER+1];
+    double ref[MAX_LPC_ORDER];
+    double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
+    int i, j, pass;
+    int opt_order;
+
+    av_assert2(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
+           lpc_type > FF_LPC_TYPE_FIXED);
+
+    /* reinit LPC context if parameters have changed */
+    if (blocksize != s->blocksize || max_order != s->max_order ||
+        lpc_type  != s->lpc_type) {
+        ff_lpc_end(s);
+        ff_lpc_init(s, blocksize, max_order, lpc_type);
+    }
+
+    if (lpc_type == FF_LPC_TYPE_LEVINSON) {
+        s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);
+
+        s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);
+
+        compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
+
+        for(i=0; i<max_order; i++)
+            ref[i] = fabs(lpc[i][i]);
+    } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
+        LLSModel m[2];
+        double var[MAX_LPC_ORDER+1], av_uninit(weight);
+
+        if(lpc_passes <= 0)
+            lpc_passes = 2;
+
+        for(pass=0; pass<lpc_passes; pass++){
+            avpriv_init_lls(&m[pass&1], max_order);
+
+            weight=0;
+            for(i=max_order; i<blocksize; i++){
+                for(j=0; j<=max_order; j++)
+                    var[j]= samples[i-j];
+
+                if(pass){
+                    double eval, inv, rinv;
+                    eval= avpriv_evaluate_lls(&m[(pass-1)&1], var+1, max_order-1);
+                    eval= (512>>pass) + fabs(eval - var[0]);
+                    inv = 1/eval;
+                    rinv = sqrt(inv);
+                    for(j=0; j<=max_order; j++)
+                        var[j] *= rinv;
+                    weight += inv;
+                }else
+                    weight++;
+
+                avpriv_update_lls(&m[pass&1], var, 1.0);
+            }
+            avpriv_solve_lls(&m[pass&1], 0.001, 0);
+        }
+
+        for(i=0; i<max_order; i++){
+            for(j=0; j<max_order; 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--)
+            ref[i] = ref[i-1] - ref[i];
+    } else
+        av_assert0(0);
+    opt_order = max_order;
+
+    if(omethod == ORDER_METHOD_EST) {
+        opt_order = estimate_best_order(ref, min_order, max_order);
+        i = opt_order-1;
+        quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
+    } else {
+        for(i=min_order-1; i<max_order; i++) {
+            quantize_lpc_coefs(lpc[i], i+1, precision, coefs[i], &shift[i], max_shift, zero_shift);
+        }
+    }
+
+    return opt_order;
+}
+
+av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
+                        enum FFLPCType lpc_type)
+{
+    s->blocksize = blocksize;
+    s->max_order = max_order;
+    s->lpc_type  = lpc_type;
+
+    if (lpc_type == FF_LPC_TYPE_LEVINSON) {
+        s->windowed_buffer = av_mallocz((blocksize + 2 + FFALIGN(max_order, 4)) *
+                                        sizeof(*s->windowed_samples));
+        if (!s->windowed_buffer)
+            return AVERROR(ENOMEM);
+        s->windowed_samples = s->windowed_buffer + FFALIGN(max_order, 4);
+    } else {
+        s->windowed_samples = NULL;
+    }
+
+    s->lpc_apply_welch_window = lpc_apply_welch_window_c;
+    s->lpc_compute_autocorr   = lpc_compute_autocorr_c;
+
+    if (ARCH_X86)
+        ff_lpc_init_x86(s);
+
+    return 0;
+}
+
+av_cold void ff_lpc_end(LPCContext *s)
+{
+    av_freep(&s->windowed_buffer);
+}
-- 
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