diff --git a/pjmedia/include/pjmedia/sdp.h b/pjmedia/include/pjmedia/sdp.h
index e2e325438d..ab25c10123 100644
--- a/pjmedia/include/pjmedia/sdp.h
+++ b/pjmedia/include/pjmedia/sdp.h
@@ -805,7 +805,13 @@ pjmedia_sdp_session_clone( pj_pool_t *pool,
 
 
 /**
- * Compare two SDP session for equality.
+ * Compare two SDP session for equality, by comparing:
+ * - the fields origin, subject, connection, time
+ * - the attributes direction, fmtp, and rtpmap
+ * - the media descriptions (see #pjmedia_sdp_media_cmp())
+ *
+ * The function will also call the callback
+ * \a pjmedia_sdp_session_cmp_cb() if registered.
  *
  * @param sd1       The first SDP session to compare.
  * @param sd2       The second SDP session to compare.
@@ -814,12 +820,46 @@ pjmedia_sdp_session_clone( pj_pool_t *pool,
  * @return          PJ_SUCCESS when both SDPs are equal, or otherwise
  *                  the status code indicates which part of the session
  *                  descriptors are not equal.
+ *                  If \a pjmedia_sdp_session_cmp_cb() is registered,
+ *                  will return the status output parameter of the callback.
  */
 PJ_DECL(pj_status_t) pjmedia_sdp_session_cmp(const pjmedia_sdp_session *sd1,
                                              const pjmedia_sdp_session *sd2,
                                              unsigned option);
 
 
+/**
+ * The declaration of customized SDP session comparison callback. See
+ * #pjmedia_sdp_session_register_cmp_cb() for more info.
+ *
+ * @param sd1       The first SDP session to compare.
+ * @param sd2       The second SDP session to compare.
+ * @param option    Must be zero for now.
+ * @param status    Status code to be returned for the SDP comparison result
+ *                  (PJ_SUCCESS meaning both SDPs are equal).
+ *                  On input, it contains the return status of
+ *                  #pjmedia_sdp_session_cmp().
+ */
+typedef void (*pjmedia_sdp_session_cmp_cb)(const pjmedia_sdp_session *sd1,
+                                           const pjmedia_sdp_session *sd2,
+                                           unsigned option,
+                                           pj_status_t *status);
+
+
+/**
+ * Register customized SDP session comparison callback. The callback will
+ * be called by #pjmedia_sdp_session_cmp().
+ * To unregister, just call this function with parameter cb set to NULL.
+ *
+ * @param cb            The customized SDP session comparison callback or
+ *                      NULL to unregister the callback.
+ *
+ * @return              PJ_SUCCESS on success.
+ */
+PJ_DECL(pj_status_t)
+pjmedia_sdp_session_register_cmp_cb(pjmedia_sdp_session_cmp_cb cb);
+
+
 /**
  * Add new attribute to the session descriptor.
  *
diff --git a/pjmedia/src/pjmedia/sdp_cmp.c b/pjmedia/src/pjmedia/sdp_cmp.c
index dfa3f33970..1d2151e4d2 100644
--- a/pjmedia/src/pjmedia/sdp_cmp.c
+++ b/pjmedia/src/pjmedia/sdp_cmp.c
@@ -22,6 +22,9 @@
 #include <pj/string.h>
 
 
+/* The registered customized SDP session comparison callback */
+static pjmedia_sdp_session_cmp_cb sdp_cmp_cb;
+
 /* Compare connection line. */
 static pj_status_t compare_conn(const pjmedia_sdp_conn *c1,
                                 const pjmedia_sdp_conn *c2)
@@ -218,12 +221,9 @@ PJ_DEF(pj_status_t) pjmedia_sdp_media_cmp( const pjmedia_sdp_media *sd1,
     return PJ_SUCCESS;
 }
 
-/*
- * Compare two SDP session for equality.
- */
-PJ_DEF(pj_status_t) pjmedia_sdp_session_cmp( const pjmedia_sdp_session *sd1,
-                                             const pjmedia_sdp_session *sd2,
-                                             unsigned option)
+static pj_status_t sdp_session_cmp(const pjmedia_sdp_session *sd1,
+                                   const pjmedia_sdp_session *sd2,
+                                   unsigned option)
 {
     unsigned i;
     pj_status_t status;
@@ -295,6 +295,30 @@ PJ_DEF(pj_status_t) pjmedia_sdp_session_cmp( const pjmedia_sdp_session *sd1,
     return PJ_SUCCESS;
 }
 
+/*
+ * Compare two SDP session for equality.
+ */
+PJ_DEF(pj_status_t) pjmedia_sdp_session_cmp( const pjmedia_sdp_session *sd1,
+                                             const pjmedia_sdp_session *sd2,
+                                             unsigned option)
+{
+    pj_status_t status;
+
+    status = sdp_session_cmp(sd1, sd2, option);
+    if (sdp_cmp_cb) {
+        (*sdp_cmp_cb)(sd1, sd2, option, &status);
+    }
+
+    return status;
+}
+
+/* Register customized SDP session comparison callback function. */
+PJ_DEF(pj_status_t)
+pjmedia_sdp_session_register_cmp_cb(pjmedia_sdp_session_cmp_cb cb)
+{
+    sdp_cmp_cb = cb;
+    return PJ_SUCCESS;
+}
 
 PJ_DEF(pj_status_t) pjmedia_sdp_conn_cmp(const pjmedia_sdp_conn *conn1, 
                                          const pjmedia_sdp_conn *conn2,