From c93ccf5a4cca722b39f05e9f5660b4cb75bc1740 Mon Sep 17 00:00:00 2001
From: Loren Merritt <lorenm@u.washington.edu>
Date: Sun, 16 Jun 2013 00:53:47 +0000
Subject: [PATCH] lpc: use levinson for the first pass of multipass cholesky

Levinson is faster, and cholesky is only needed if we want to apply different
weights to different samples, which doesn't happen on the first pass.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
---
 libavcodec/lpc.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/libavcodec/lpc.c b/libavcodec/lpc.c
index 144bbed..995e4e2 100644
--- a/libavcodec/lpc.c
+++ b/libavcodec/lpc.c
@@ -176,7 +176,7 @@ int ff_lpc_calc_coefs(LPCContext *s,
     double autoc[MAX_LPC_ORDER+1];
     double ref[MAX_LPC_ORDER];
     double lpc[MAX_LPC_ORDER][MAX_LPC_ORDER];
-    int i, j, pass;
+    int i, j, pass = 0;
     int opt_order;
 
     assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
@@ -189,7 +189,7 @@ int ff_lpc_calc_coefs(LPCContext *s,
         ff_lpc_init(s, blocksize, max_order, lpc_type);
     }
 
-    if (lpc_type == FF_LPC_TYPE_LEVINSON) {
+    if (lpc_type == FF_LPC_TYPE_LEVINSON || (lpc_type == FF_LPC_TYPE_CHOLESKY && lpc_passes > 1)) {
         s->lpc_apply_welch_window(samples, blocksize, s->windowed_samples);
 
         s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);
@@ -198,13 +198,20 @@ int ff_lpc_calc_coefs(LPCContext *s,
 
         for(i=0; i<max_order; i++)
             ref[i] = fabs(lpc[i][i]);
-    } else if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
+
+        pass++;
+    }
+
+    if (lpc_type == FF_LPC_TYPE_CHOLESKY) {
         LLSModel m[2];
         LOCAL_ALIGNED(32, double, var, [FFALIGN(MAX_LPC_ORDER+1,4)]);
         double av_uninit(weight);
         memset(var, 0, FFALIGN(MAX_LPC_ORDER+1,4)*sizeof(*var));
 
-        for(pass=0; pass<lpc_passes; pass++){
+        for(j=0; j<max_order; j++)
+            m[0].coeff[max_order-1][j] = -lpc[max_order-1][j];
+
+        for(; pass<lpc_passes; pass++){
             avpriv_init_lls(&m[pass&1], max_order);
 
             weight=0;
@@ -259,15 +266,11 @@ av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
     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->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);
 
     s->lpc_apply_welch_window = lpc_apply_welch_window_c;
     s->lpc_compute_autocorr   = lpc_compute_autocorr_c;
-- 
2.7.4