Changeset 3837 for pjproject/trunk/pjmedia/src/pjmedia/sdp_neg.c

Timestamp:

Oct 23, 2011 6:59:48 AM (12 years ago)

Author:

nanang

Message:

Re #1300: Implemented symmetric payload type in generating SDP answer in SDP negotiator.
This should work for all codecs, audio & video. Can be disabled at compile-time
using PJMEDIA_SDP_NEG_REWRITE_ANSWER_PT macro setting.

File:

• pjproject/trunk/pjmedia/src/pjmedia/sdp_neg.c (modified) (6 diffs)

pjproject/trunk/pjmedia/src/pjmedia/sdp_neg.c

@@ -1121 +1121 @@
 }
 
+
+/* Internal function to rewrite the format string in SDP attribute rtpmap
+ * and fmtp.
+ */
+PJ_INLINE(void) rewrite_pt(pj_pool_t *pool, pj_str_t *attr_val,
+                           const pj_str_t *old_pt, const pj_str_t *new_pt)
+{
+    int len_diff = new_pt->slen - old_pt->slen;
+
+    /* Note that attribute value should be null-terminated. */
+    if (len_diff > 0) {
+        pj_str_t new_val;
+        new_val.ptr = (char*)pj_pool_alloc(pool, attr_val->slen+len_diff+1);
+        new_val.slen = attr_val->slen + len_diff;
+        pj_memcpy(new_val.ptr + len_diff, attr_val->ptr, attr_val->slen + 1);
+        *attr_val = new_val;
+    } else if (len_diff < 0) {
+        pj_memmove(attr_val->ptr, attr_val->ptr - len_diff,
+                   attr_val->slen + len_diff + 1);
+    }
+    pj_memcpy(attr_val->ptr, new_pt->ptr, new_pt->slen);
+}
+
+
+/* Internal function to apply symmetric PT for the local answer. */
+static void apply_answer_symmetric_pt(pj_pool_t *pool,
+                                      pjmedia_sdp_media *answer,
+                                      unsigned pt_cnt,
+                                      const pj_str_t pt_offer[],
+                                      const pj_str_t pt_answer[])
+{
+    pjmedia_sdp_attr *a_tmp[PJMEDIA_MAX_SDP_ATTR];
+    unsigned i, a_tmp_cnt = 0;
+
+    /* Rewrite the payload types in the answer if different to
+     * the ones in the offer.
+     */
+    for (i = 0; i < pt_cnt; ++i) {
+        pjmedia_sdp_attr *a;
+
+        /* Skip if the PTs are the same already, e.g: static PT. */
+        if (pj_strcmp(&pt_answer[i], &pt_offer[i]) == 0)
+            continue;
+
+        /* Rewrite payload type in the answer to match to the offer */
+        pj_strdup(pool, &answer->desc.fmt[i], &pt_offer[i]);
+
+        /* Also update payload type in rtpmap */
+        a = pjmedia_sdp_media_find_attr2(answer, "rtpmap", &pt_answer[i]);
+        if (a) {
+            rewrite_pt(pool, &a->value, &pt_answer[i], &pt_offer[i]);
+            /* Temporarily remove the attribute in case the new payload
+             * type is being used by another format in the media.
+             */
+            pjmedia_sdp_media_remove_attr(answer, a);
+            a_tmp[a_tmp_cnt++] = a;
+        }
+
+        /* Also update payload type in fmtp */
+        a = pjmedia_sdp_media_find_attr2(answer, "fmtp", &pt_answer[i]);
+        if (a) {
+            rewrite_pt(pool, &a->value, &pt_answer[i], &pt_offer[i]);
+            /* Temporarily remove the attribute in case the new payload
+             * type is being used by another format in the media.
+             */
+            pjmedia_sdp_media_remove_attr(answer, a);
+            a_tmp[a_tmp_cnt++] = a;
+        }
+    }
+
+    /* Return back 'rtpmap' and 'fmtp' attributes */
+    for (i = 0; i < a_tmp_cnt; ++i)
+        pjmedia_sdp_media_add_attr(answer, a_tmp[i]);
+}
+
+
 /* Try to match offer with answer. */
 static pj_status_t match_offer(pj_pool_t *pool,
@@ -1138 +1214 @@
     unsigned pt_answer_count = 0;
     pj_str_t pt_answer[PJMEDIA_MAX_SDP_FMT];
+    pj_str_t pt_offer[PJMEDIA_MAX_SDP_FMT];
     pjmedia_sdp_media *answer;
     const pjmedia_sdp_media *master, *slave;
@@ -1202 +1279 @@
                     if (p == pt && pj_isdigit(*slave->desc.fmt[j].ptr)) {
                         found_matching_codec = 1;
+                        pt_offer[pt_answer_count] = slave->desc.fmt[j];
                         pt_answer[pt_answer_count++] = slave->desc.fmt[j];
                         break;
@@ -1301 +1379 @@
                             }
 
+                            pt_offer[pt_answer_count] = 
+                                                prefer_remote_codec_order?
+                                                offer->desc.fmt[i]:
+                                                offer->desc.fmt[j];
                             pt_answer[pt_answer_count++] = 
                                                 prefer_remote_codec_order? 
@@ -1326 +1408 @@
                     /* Match */
                     found_matching_other = 1;
+                    pt_offer[pt_answer_count] = prefer_remote_codec_order?
+                                                offer->desc.fmt[i]:
+                                                offer->desc.fmt[j];
                     pt_answer[pt_answer_count++] = prefer_remote_codec_order? 
                                                    preanswer->desc.fmt[j]:
@@ -1390 +1475 @@
     }
     answer->desc.fmt_count = pt_answer_count;
+
+#if PJMEDIA_SDP_NEG_ANSWER_SYMMETRIC_PT
+    apply_answer_symmetric_pt(pool, answer, pt_answer_count,
+                              pt_offer, pt_answer);
+#endif
 
     /* Update media direction. */