From 6662568c1154d1bc2a835255576dd258510ea8fb Mon Sep 17 00:00:00 2001
From: "jinxue.cgh" <jinxue.cgh@alibaba-inc.com>
Date: Sat, 27 Jun 2020 17:06:33 +0800
Subject: [PATCH] RTC: sdp surpport ssrc group encode and decode

---
 trunk/src/app/srs_app_rtc_sdp.cpp | 52 +++++++++++++++++++++++++++++--
 trunk/src/app/srs_app_rtc_sdp.hpp | 11 +++++++
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/trunk/src/app/srs_app_rtc_sdp.cpp b/trunk/src/app/srs_app_rtc_sdp.cpp
index 4c3d9f53c..5e2a584fd 100644
--- a/trunk/src/app/srs_app_rtc_sdp.cpp
+++ b/trunk/src/app/srs_app_rtc_sdp.cpp
@@ -206,6 +206,40 @@ srs_error_t SrsSSRCInfo::encode(std::ostringstream& os)
     return err;
 }
 
+SrsSSRCGroup::SrsSSRCGroup()
+{
+}
+
+SrsSSRCGroup::~SrsSSRCGroup()
+{
+}
+
+SrsSSRCGroup::SrsSSRCGroup(const std::string& semantic, const std::vector<uint32_t>& ssrcs)
+{
+    semantic_ = semantic;
+    ssrcs_ = ssrcs;
+}
+
+srs_error_t SrsSSRCGroup::encode(std::ostringstream& os)
+{
+    srs_error_t err = srs_success;
+
+    if (semantic_.empty()) {
+        return srs_error_new(ERROR_RTC_SDP_DECODE, "invalid semantics");
+    }
+
+    if (ssrcs_.size() == 0) {
+        return srs_error_new(ERROR_RTC_SDP_DECODE, "invalid ssrcs");
+    }
+
+    os << "a=ssrc-group:" << semantic_;
+    for (int i = 0; i < (int)ssrcs_.size(); i++) {
+        os << " " << ssrcs_[i];
+    }
+
+    return err;
+}
+
 SrsMediaPayloadType::SrsMediaPayloadType(int payload_type)
 {
     payload_type_ = payload_type;
@@ -589,6 +623,7 @@ srs_error_t SrsMediaDesc::parse_attr_ssrc(const std::string& value)
         ssrc_info.cname_ = ssrc_value;
         ssrc_info.ssrc_ = ssrc;
     } else if (ssrc_attr == "msid") {
+        // @see: https://tools.ietf.org/html/draft-alvestrand-mmusic-msid-00#section-2
         std::vector<std::string> vec = split_str(ssrc_value, " ");
         if (vec.empty()) {
             return srs_error_new(ERROR_RTC_SDP_DECODE, "invalid ssrc line=%s", value.c_str());
@@ -618,10 +653,23 @@ srs_error_t SrsMediaDesc::parse_attr_ssrc_group(const std::string& value)
     std::string semantics;
     FETCH(is, semantics);
 
-    // TODO: ssrc group process
-    if (semantics == "FID") {
+    std::string ssrc_ids = is.str().substr(is.tellg());
+    skip_first_spaces(ssrc_ids);
+
+    std::vector<std::string> vec = split_str(ssrc_ids, " ");
+    if (vec.size() == 0) {
+        return srs_error_new(ERROR_RTC_SDP_DECODE, "invalid ssrc-group line=%s", value.c_str());
     }
 
+    std::vector<uint32_t> ssrcs;
+    for (size_t i = 0; i < vec.size(); ++i) {
+        std::istringstream in_stream(vec[i]);
+        uint32_t ssrc = 0;
+        in_stream >> ssrc;
+        ssrcs.push_back(ssrc);
+    }
+    ssrc_groups_.push_back(SrsSSRCGroup(semantics, ssrcs));
+
     return err;
 }
 
diff --git a/trunk/src/app/srs_app_rtc_sdp.hpp b/trunk/src/app/srs_app_rtc_sdp.hpp
index b923affc5..c09af3ee0 100644
--- a/trunk/src/app/srs_app_rtc_sdp.hpp
+++ b/trunk/src/app/srs_app_rtc_sdp.hpp
@@ -78,6 +78,17 @@ public:
 
 class SrsSSRCGroup
 {
+public:
+    SrsSSRCGroup();
+    SrsSSRCGroup(const std::string& usage, const std::vector<uint32_t>& ssrcs);
+    virtual ~SrsSSRCGroup();
+public:
+    srs_error_t encode(std::ostringstream& os);
+public:
+    // e.g FIX, FEC, SIM.
+    std::string semantic_;
+    // SSRCs of this type. 
+    std::vector<uint32_t> ssrcs_;
 };
 
 struct H264SpecificParam