1 files changed, 118 insertions, 0 deletions
diff --git a/gst/law/mulaw-conversion.c b/gst/law/mulaw-conversion.c
new file mode 100644
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+++ b/gst/law/mulaw-conversion.c
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+/*
+ * This routine converts from linear to ulaw
+ * 29 September 1989
+ *
+ * Craig Reese: IDA/Supercomputing Research Center
+ * Joe Campbell: Department of Defense
+ *
+ * References:
+ * 1) CCITT Recommendation G.711  (very difficult to follow)
+ * 2) "A New Digital Technique for Implementation of Any 
+ *     Continuous PCM Companding Law," Villeret, Michel,
+ *     et al. 1973 IEEE Int. Conf. on Communications, Vol 1,
+ *     1973, pg. 11.12-11.17
+ * 3) MIL-STD-188-113,"Interoperability and Performance Standards
+ *     for Analog-to_Digital Conversion Techniques,"
+ *     17 February 1987
+ *
+ * Input: Signed 16 bit linear sample
+ * Output: 8 bit ulaw sample
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <glib.h>
+
+#include "mulaw-conversion.h"
+
+#undef ZEROTRAP                 /* turn on the trap as per the MIL-STD */
+#define BIAS 0x84               /* define the add-in bias for 16 bit samples */
+#define CLIP 32635
+
+void
+mulaw_encode (gint16 * in, guint8 * out, gint numsamples)
+{
+  static gint16 exp_lut[256] = { 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
+    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
+    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
+    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
+    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+    6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
+    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
+  };
+  gint16 sign, exponent, mantissa, i;
+  gint16 sample;
+  guint8 ulawbyte;
+
+  for (i = 0; i < numsamples; i++) {
+    sample = in[i];
+      /** get the sample into sign-magnitude **/
+    sign = (sample >> 8) & 0x80;        /* set aside the sign */
+    if (sign != 0) {
+      sample = -sample;         /* get magnitude */
+    }
+    /* sample can be zero because we can overflow in the inversion,
+     * checking against the unsigned version solves this */
+    if (((guint16) sample) > CLIP)
+      sample = CLIP;            /* clip the magnitude */
+
+      /** convert from 16 bit linear to ulaw **/
+    sample = sample + BIAS;
+    exponent = exp_lut[(sample >> 7) & 0xFF];
+    mantissa = (sample >> (exponent + 3)) & 0x0F;
+    ulawbyte = ~(sign | (exponent << 4) | mantissa);
+#ifdef ZEROTRAP
+    if (ulawbyte == 0)
+      ulawbyte = 0x02;          /* optional CCITT trap */
+#endif
+    out[i] = ulawbyte;
+  }
+}
+
+/*
+ * This routine converts from ulaw to 16 bit linear
+ * 29 September 1989
+ *
+ * Craig Reese: IDA/Supercomputing Research Center
+ *
+ * References:
+ * 1) CCITT Recommendation G.711  (very difficult to follow)
+ * 2) MIL-STD-188-113,"Interoperability and Performance Standards
+ *     for Analog-to_Digital Conversion Techniques,"
+ *     17 February 1987
+ *
+ * Input: 8 bit ulaw sample
+ * Output: signed 16 bit linear sample
+ */
+
+void
+mulaw_decode (guint8 * in, gint16 * out, gint numsamples)
+{
+  static gint16 exp_lut[8] = { 0, 132, 396, 924, 1980, 4092, 8316, 16764 };
+  gint16 sign, exponent, mantissa;
+  guint8 ulawbyte;
+  gint16 linear, i;
+
+  for (i = 0; i < numsamples; i++) {
+    ulawbyte = in[i];
+    ulawbyte = ~ulawbyte;
+    sign = (ulawbyte & 0x80);
+    exponent = (ulawbyte >> 4) & 0x07;
+    mantissa = ulawbyte & 0x0F;
+    linear = exp_lut[exponent] + (mantissa << (exponent + 3));
+    if (sign != 0)
+      linear = -linear;
+    out[i] = linear;
+  }
+}