Changeset 931 for pjproject/trunk/pjmedia/src/pjmedia/conference.c

Timestamp:

Feb 4, 2007 5:04:33 PM (17 years ago)

Author:

bennylp

Message:

Fixed ticket #78: Noise in conference bridge because of upsampling and changes in audio level

File:

• pjproject/trunk/pjmedia/src/pjmedia/conference.c (modified) (3 diffs)

pjproject/trunk/pjmedia/src/pjmedia/conference.c

@@ -68 +68 @@
 
 
+/* These are settings to control the adaptivity of changes in the
+ * signal level of the ports, so that sudden change in signal level
+ * in the port does not cause misaligned signal (which causes noise).
+ */
+#if 1
+#   define ATTACK_A         3
+#   define ATTACK_B         2
+#   define DECAY_A          3
+#   define DECAY_B          2
+#else
+    /* To simulate old behavior */
+#   define ATTACK_A         0
+#   define ATTACK_B         1
+#   define DECAY_A          0
+#   define DECAY_B          1
+#endif
+
+
+
 /*
  * DON'T GET CONFUSED WITH TX/RX!!
@@ -95 +114 @@
     unsigned             clock_rate;    /**< Port's clock rate.             */
     unsigned             samples_per_frame; /**< Port's samples per frame.  */
+
+    /* Last level calculated from this port */
+    pj_int32_t           last_level;
 
     /* Calculated signal levels: */
@@ -1717 +1739 @@
         }
 
+        /* Apply simple AGC to the level, to avoid dramatic change in the
+         * level thus causing noise because the signal now is not aligned
+         * with the signal from the previous frame.
+         */
+        if (level >= conf_port->last_level) {
+            level = (conf_port->last_level * ATTACK_A + level * ATTACK_B) / 
+                    (ATTACK_A + ATTACK_B);
+        } else {
+            level = (conf_port->last_level * DECAY_A + level * DECAY_B) / 
+                    (DECAY_A + DECAY_B);
+        }
+        conf_port->last_level = level;
+
+
         /* Convert level to 8bit complement ulaw */
         level = pjmedia_linear2ulaw(level) ^ 0xff;