avcodec/lpc: Split inline functions into a header of their own

And move compute_ref_coefs() to its only user: lpc.c
There is no overlap between the users of compute_lpc_coefs()
and lpc proper.

Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

1 files changed, 100 insertions, 0 deletions

diff --git a/libavcodec/lpc_functions.h b/libavcodec/lpc_functions.h
new file mode 100644
index 0000000000..57bcfab900
--- /dev/null
+++ b/libavcodec/lpc_functions.h
@@ -0,0 +1,100 @@
+/*
+ * LPC utility functions
+ * 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
+ */
+
+#ifndef AVCODEC_LPC_FUNCTIONS_H
+#define AVCODEC_LPC_FUNCTIONS_H
+
+#include "libavutil/avassert.h"
+
+#ifndef LPC_USE_FIXED
+#define LPC_USE_FIXED 0
+#endif
+
+#if LPC_USE_FIXED
+typedef int LPC_TYPE;
+typedef unsigned LPC_TYPE_U;
+#else
+#ifndef LPC_SRA_R
+#define LPC_SRA_R(x, y) (x)
+#define LPC_MUL26(x, y) ((x) * (y))
+#define LPC_FIXR(x)     ((float)(x))
+#endif
+
+#ifdef LPC_USE_DOUBLE
+typedef double LPC_TYPE;
+typedef double LPC_TYPE_U;
+#else
+typedef float LPC_TYPE;
+typedef float LPC_TYPE_U;
+#endif
+#endif // USE_FIXED
+
+/**
+ * Levinson-Durbin recursion.
+ * Produce 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)
+{
+    LPC_TYPE err = 0;
+    LPC_TYPE *lpc_last = lpc;
+
+    av_assert2(normalize || !fail);
+
+    if (normalize)
+        err = *autoc++;
+
+    if (fail && (autoc[max_order - 1] == 0 || err <= 0))
+        return -1;
+
+    for(int i = 0; i < max_order; i++) {
+        LPC_TYPE r = LPC_SRA_R(-autoc[i], 5);
+
+        if (normalize) {
+            for(int j = 0; j < i; j++)
+                r -= lpc_last[j] * autoc[i-j-1];
+
+            if (err)
+                r /= err;
+            err *= LPC_FIXR(1.0) - (r * r);
+        }
+
+        lpc[i] = r;
+
+        for(int j = 0; j < (i + 1) >> 1; j++) {
+            LPC_TYPE f = lpc_last[    j];
+            LPC_TYPE b = lpc_last[i-1-j];
+            lpc[    j] = f + (LPC_TYPE_U)LPC_MUL26(r, b);
+            lpc[i-1-j] = b + (LPC_TYPE_U)LPC_MUL26(r, f);
+        }
+
+        if (fail && err < 0)
+            return -1;
+
+        lpc_last = lpc;
+        lpc += lpc_stride;
+    }
+
+    return 0;
+}
+
+#endif /* AVCODEC_LPC_FUNCTIONS_H */