完善ertmp相关代码 (#4505)

增加多种Codec支持，并修复一些bug：
- opus 非标准实现，不输出config frame，与旧的实现保持一致
- 添加RTMP_CODEC_MAP宏，精简代码

src/Rtmp/Rtmp.cpp

@@ -55,6 +55,33 @@ AudioMeta::AudioMeta(const AudioTrack::Ptr &audio) {
     _metadata.set("audiocodecid", Factory::getAmfByCodecId(audio->getCodecId()));
 }
 
+uint8_t getCodecFlags(CodecId cid) {
+    switch(cid) {
+#define XX(a, b, c) case a: return static_cast<uint8_t>(b);
+    RTMP_CODEC_MAP(XX)
+#undef XX
+    }
+    return 0;
+}
+
+uint32_t getCodecFourCC(CodecId cid) {
+    switch(cid) {
+#define XX(a, b, c) case a: return static_cast<uint32_t>(c);
+    RTMP_CODEC_MAP(XX)
+#undef XX
+    }
+    return 0;
+}
+
+CodecId getFourccCodec(uint32_t id) {
+    switch(id) {
+#define XX(a, b, c) case (uint32_t)c: return a;
+    RTMP_CODEC_MAP(XX)
+#undef XX
+    }
+    return CodecInvalid;
+}
+
 uint8_t getAudioRtmpFlags(const Track::Ptr &track) {
     track->update();
     switch (track->getTrackType()) {
@@ -167,7 +194,13 @@ bool RtmpPacket::isVideoKeyFrame() const {
 bool RtmpPacket::isConfigFrame() const {
     switch (type_id) {
         case MSG_AUDIO: {
-            return (RtmpAudioCodec)getRtmpCodecId() == RtmpAudioCodec::aac && (RtmpAACPacketType)buffer[1] == RtmpAACPacketType::aac_config_header;
+            switch ((RtmpAudioCodec)getRtmpCodecId()) {
+            case RtmpAudioCodec::aac:
+                return (RtmpAACPacketType)buffer[1] == RtmpAACPacketType::aac_config_header;
+            case RtmpAudioCodec::ex_header:
+                return (RtmpPacketType)(buffer[0] & 0x0f) == RtmpPacketType::PacketTypeSequenceStart;
+            }
+            return false;
         }
         case MSG_VIDEO: {
             if (!isVideoKeyFrame()) {