Allow NetEQ to use real packet durations.

This is a copy of http://review.webrtc.org/864014/

This adds a FuncDurationEst to each codec instance which estimates
the duration of a packet given the packet contents and the duration
of the previous packet. By default, this simply returns the
duration of the previous packet (which is what is currently assumed
to be the duration of all future packets). This patch also provides
an initial implementation of this function for G.711 which returns
the actual number of samples in the packet.

BUG=issue1015

Review URL: https://webrtc-codereview.appspot.com/935016

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3129 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/codecs/g711/g711_interface.c

@@ -164,6 +164,16 @@ WebRtc_Word16 WebRtcG711_DecodeU(void *state,
     return (len);
 }
 
+int WebRtcG711_DurationEst(void* state,
+                           const uint8_t* payload,
+                           int payload_length_bytes) {
+    (void)state;
+    (void)payload;
+    /* G.711 is one byte per sample, so we can just return the number of
+       bytes. */
+    return payload_length_bytes;
+}
+
 WebRtc_Word16 WebRtcG711_Version(char* version, WebRtc_Word16 lenBytes)
 {
     strncpy(version, "2.0.0", lenBytes);

webrtc/modules/audio_coding/codecs/g711/include/g711_interface.h

@@ -123,6 +123,27 @@ WebRtc_Word16 WebRtcG711_DecodeU(void *state,
                                  WebRtc_Word16 *decoded,
                                  WebRtc_Word16 *speechType);
 
+
+/****************************************************************************
+ * WebRtcG711_DurationEst(...)
+ *
+ * This function estimates the duration of a G711 packet in samples.
+ *
+ * Input:
+ *      - state              : Dummy state to make this codec look more like
+ *                             other codecs
+ *      - payload            : Encoded data
+ *      - payloadLengthBytes : Bytes in encoded vector
+ *
+ * Return value              : The duration of the packet in samples, which is
+ *                             just payload_length_bytes, since G.711 uses one
+ *                             byte per sample.
+ */
+
+int WebRtcG711_DurationEst(void* state,
+                           const uint8_t* payload,
+                           int payload_length_bytes);
+
 /**********************************************************************
 * WebRtcG711_Version(...)
 *