Allow hardcoding of ulaw and alaw tables.

Originally committed as revision 22762 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 119 insertions, 0 deletions

diff --git a/libavcodec/pcm_tablegen.h b/libavcodec/pcm_tablegen.h
new file mode 100644
index 0000000000..8921baaba2
--- /dev/null
+++ b/libavcodec/pcm_tablegen.h
@@ -0,0 +1,119 @@
+/*
+ * Header file for hardcoded PCM tables
+ *
+ * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
+ *
+ * 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 PCM_TABLEGEN_H
+#define PCM_TABLEGEN_H
+
+#include <stdint.h>
+#include "../libavutil/attributes.h"
+
+/* from g711.c by SUN microsystems (unrestricted use) */
+
+#define         SIGN_BIT        (0x80)      /* Sign bit for a A-law byte. */
+#define         QUANT_MASK      (0xf)       /* Quantization field mask. */
+#define         NSEGS           (8)         /* Number of A-law segments. */
+#define         SEG_SHIFT       (4)         /* Left shift for segment number. */
+#define         SEG_MASK        (0x70)      /* Segment field mask. */
+
+#define         BIAS            (0x84)      /* Bias for linear code. */
+
+/*
+ * alaw2linear() - Convert an A-law value to 16-bit linear PCM
+ *
+ */
+static av_cold int alaw2linear(unsigned char a_val)
+{
+        int t;
+        int seg;
+
+        a_val ^= 0x55;
+
+        t = a_val & QUANT_MASK;
+        seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
+        if(seg) t= (t + t + 1 + 32) << (seg + 2);
+        else    t= (t + t + 1     ) << 3;
+
+        return (a_val & SIGN_BIT) ? t : -t;
+}
+
+static av_cold int ulaw2linear(unsigned char u_val)
+{
+        int t;
+
+        /* Complement to obtain normal u-law value. */
+        u_val = ~u_val;
+
+        /*
+         * Extract and bias the quantization bits. Then
+         * shift up by the segment number and subtract out the bias.
+         */
+        t = ((u_val & QUANT_MASK) << 3) + BIAS;
+        t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
+
+        return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
+}
+
+#if CONFIG_HARDCODED_TABLES
+#define pcm_alaw_tableinit()
+#define pcm_ulaw_tableinit()
+#include "libavcodec/pcm_tables.h"
+#else
+/* 16384 entries per table */
+static uint8_t linear_to_alaw[16384];
+static uint8_t linear_to_ulaw[16384];
+
+static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
+                             int (*xlaw2linear)(unsigned char),
+                             int mask)
+{
+    int i, j, v, v1, v2;
+
+    j = 0;
+    for(i=0;i<128;i++) {
+        if (i != 127) {
+            v1 = xlaw2linear(i ^ mask);
+            v2 = xlaw2linear((i + 1) ^ mask);
+            v = (v1 + v2 + 4) >> 3;
+        } else {
+            v = 8192;
+        }
+        for(;j<v;j++) {
+            linear_to_xlaw[8192 + j] = (i ^ mask);
+            if (j > 0)
+                linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80));
+        }
+    }
+    linear_to_xlaw[0] = linear_to_xlaw[1];
+}
+
+static void pcm_alaw_tableinit(void)
+{
+    build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
+}
+
+static void pcm_ulaw_tableinit(void)
+{
+    build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
+}
+#endif /* CONFIG_HARDCODED_TABLES */
+
+#endif /* PCM_TABLEGEN_H */