Expose QCELP's floating-point LSP-to-LPC function

qcelp_lsp exported a single function, ff_acelp_lspd2lpc, which was not
specific to qcelp. It can be kept with its fixed-point version
ff_acelp_lsp2lpc in lpc.c.

Patch by Colin McQuillan ( m.niloc googlemail com )

Originally committed as revision 19571 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/Makefile

@@ -177,7 +177,7 @@ OBJS-$(CONFIG_PNG_ENCODER)             += png.o pngenc.o
 OBJS-$(CONFIG_PPM_DECODER)             += pnmenc.o pnm.o
 OBJS-$(CONFIG_PPM_ENCODER)             += pnmenc.o
 OBJS-$(CONFIG_PTX_DECODER)             += ptx.o
-OBJS-$(CONFIG_QCELP_DECODER)           += qcelpdec.o qcelp_lsp.o celp_math.o celp_filters.o acelp_vectors.o
+OBJS-$(CONFIG_QCELP_DECODER)           += qcelpdec.o lsp.o celp_math.o celp_filters.o acelp_vectors.o
 OBJS-$(CONFIG_QDM2_DECODER)            += qdm2.o mpegaudiodec.o mpegaudiodecheader.o mpegaudio.o mpegaudiodata.o
 OBJS-$(CONFIG_QDRAW_DECODER)           += qdrw.o
 OBJS-$(CONFIG_QPEG_DECODER)            += qpeg.o

libavcodec/lsp.c

@@ -1,6 +1,7 @@
 /*
  * LSP routines for ACELP-based codecs
  *
+ * Copyright (c) 2007 Reynaldo H. Verdejo Pinochet (QCELP decoder)
  * Copyright (c) 2008 Vladimir Voroshilov
  *
  * This file is part of FFmpeg.
@@ -118,3 +119,48 @@ void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd
     /* LSP values for second subframe (3.2.5 of G.729)*/
     ff_acelp_lsp2lpc(lp_2nd, lsp_2nd, lp_order >> 1);
 }
+
+/**
+ * Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients
+ * needed for LSP to LPC conversion.
+ * We only need to calculate the 6 first elements of the polynomial.
+ *
+ * @param lsp line spectral pairs in cosine domain
+ * @param f [out] polynomial input/output as a vector
+ *
+ * TIA/EIA/IS-733 2.4.3.3.5-1/2
+ */
+static void lsp2polyf(const double *lsp, double *f, int lp_half_order)
+{
+    int i, j;
+
+    f[0] = 1.0;
+    f[1] = -2 * lsp[0];
+    lsp -= 2;
+    for(i=2; i<=lp_half_order; i++)
+    {
+        double val = -2 * lsp[2*i];
+        f[i] = val * f[i-1] + 2*f[i-2];
+        for(j=i-1; j>1; j--)
+            f[j] += f[j-1] * val + f[j-2];
+        f[1] += val;
+    }
+}
+
+void ff_acelp_lspd2lpc(const double *lsp, float *lpc)
+{
+    double pa[6], qa[6];
+    int   i;
+
+    lsp2polyf(lsp,     pa, 5);
+    lsp2polyf(lsp + 1, qa, 5);
+
+    for (i=4; i>=0; i--)
+    {
+        double paf = pa[i+1] + pa[i];
+        double qaf = qa[i+1] - qa[i];
+
+        lpc[i  ] = 0.5*(paf+qaf);
+        lpc[9-i] = 0.5*(paf-qaf);
+    }
+}

libavcodec/lsp.h

@@ -67,4 +67,14 @@ void ff_acelp_lsp2lpc(int16_t* lp, const int16_t* lsp, int lp_half_order);
  */
 void ff_acelp_lp_decode(int16_t* lp_1st, int16_t* lp_2nd, const int16_t* lsp_2nd, const int16_t* lsp_prev, int lp_order);
 
+/**
+ * Reconstructs LPC coefficients from the line spectral pair frequencies.
+ *
+ * @param lsp line spectral pairs in cosine domain
+ * @param lpc linear predictive coding coefficients
+ *
+ * TIA/EIA/IS-733 2.4.3.3.5
+ */
+void ff_acelp_lspd2lpc(const double *lsp, float *lpc);
+
 #endif /* AVCODEC_LSP_H */

libavcodec/qcelp_lsp.c

@@ -1,81 +0,0 @@
-/*
- * QCELP decoder
- * Copyright (c) 2007 Reynaldo H. Verdejo Pinochet
- *
- * 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
- */
-
-/**
- * @file libavcodec/qcelp_lsp.c
- * QCELP decoder
- * @author Reynaldo H. Verdejo Pinochet
- * @remark FFmpeg merging spearheaded by Kenan Gillet
- * @remark Development mentored by Benjamin Larson
- */
-
-#include "libavutil/mathematics.h"
-
-/**
- * Computes the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients
- * needed for LSP to LPC conversion.
- * We only need to calculate the 6 first elements of the polynomial.
- *
- * @param lsp line spectral pairs in cosine domain
- * @param f [out] polynomial input/output as a vector
- *
- * TIA/EIA/IS-733 2.4.3.3.5-1/2
- */
-static void lsp2polyf(const double *lsp, double *f, int lp_half_order)
-{
-    int i, j;
-
-    f[0] = 1.0;
-    f[1] = -2 * lsp[0];
-    lsp -= 2;
-    for(i=2; i<=lp_half_order; i++)
-    {
-        double val = -2 * lsp[2*i];
-        f[i] = val * f[i-1] + 2*f[i-2];
-        for(j=i-1; j>1; j--)
-            f[j] += f[j-1] * val + f[j-2];
-        f[1] += val;
-    }
-}
-
-/**
- * Reconstructs LPC coefficients from the line spectral pair frequencies.
- *
- * @param lsp line spectral pairs in cosine domain
- * @param lpc linear predictive coding coefficients
- */
-void ff_acelp_lspd2lpc(const double *lsp, float *lpc)
-{
-    double pa[6], qa[6];
-    int   i;
-
-    lsp2polyf(lsp,     pa, 5);
-    lsp2polyf(lsp + 1, qa, 5);
-
-    for (i=4; i>=0; i--)
-    {
-        double paf = pa[i+1] + pa[i];
-        double qaf = qa[i+1] - qa[i];
-
-        lpc[i  ] = 0.5*(paf+qaf);
-        lpc[9-i] = 0.5*(paf-qaf);
-    }
-}

libavcodec/qcelpdec.c

@@ -38,6 +38,7 @@
 #include "celp_math.h"
 #include "celp_filters.h"
 #include "acelp_vectors.h"
+#include "lsp.h"
 
 #undef NDEBUG
 #include <assert.h>
@@ -75,13 +76,6 @@ typedef struct
     uint8_t  warned_buf_mismatch_bitrate;
 } QCELPContext;
 
-/**
- * Reconstructs LPC coefficients from the line spectral pair frequencies.
- *
- * TIA/EIA/IS-733 2.4.3.3.5
- */
-void ff_acelp_lspd2lpc(const double *lsp, float *lpc);
-
 /**
  * Initialize the speech codec according to the specification.
  *