From 8d454dade2d60dbaefa809eb8190e32d38497af6 Mon Sep 17 00:00:00 2001
From: Martin Pulec <martin.pulec@cesnet.cz>
Date: Wed, 11 Nov 2020 13:29:51 +0100
Subject: [PATCH] SDP: Set correct IP version

+ some documentation
---
 src/main.cpp                | 2 +-
 src/utils/sdp.c             | 6 +++---
 src/video_rxtx/h264_sdp.cpp | 8 +++++++-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 01414b2e4..4d5f9a59a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1114,7 +1114,7 @@ int main(int argc, char *argv[])
                         audio_codec = "OPUS:sample_rate=48000";
                 }
                 if (requested_compression == nullptr) {
-                        requested_compression = "none"; // will be set later
+                        requested_compression = "none"; // will be set later by h264_sdp_video_rxtx::send_frame()
                 }
                 if (force_ip_version == 0 && strcasecmp(video_protocol, "rtsp") == 0) {
                         force_ip_version = 4;
diff --git a/src/utils/sdp.c b/src/utils/sdp.c
index 7416f1841..6e95e2d8b 100644
--- a/src/utils/sdp.c
+++ b/src/utils/sdp.c
@@ -106,7 +106,7 @@ struct sdp {
 };
 
 struct sdp *new_sdp(int ip_version, const char *receiver) {
-    assert(ip_version == 0 || ip_version == 4 || ip_version == 6);
+    assert(ip_version == 4 || ip_version == 6);
     struct sdp *sdp;
     sdp = calloc(1, sizeof(struct sdp));
     assert(sdp != NULL);
@@ -137,9 +137,9 @@ struct sdp *new_sdp(int ip_version, const char *receiver) {
         connection_address = receiver;
     }
     strncpy(sdp->version, "v=0\n", STR_LENGTH - 1);
-    snprintf(sdp->origin, STR_LENGTH, "o=- 0 0 IN IP%d %s\n", ip_version == 0 ? 4 : 6, origin_address);
+    snprintf(sdp->origin, STR_LENGTH, "o=- 0 0 IN IP%d %s\n", ip_version, origin_address);
     strncpy(sdp->session_name, "s=Ultragrid streams\n", STR_LENGTH - 1);
-    snprintf(sdp->connection, STR_LENGTH, "c=IN IP%d %s\n", ip_version == 0 ? 4 : 6, connection_address);
+    snprintf(sdp->connection, STR_LENGTH, "c=IN IP%d %s\n", ip_version, connection_address);
     strncpy(sdp->times, "t=0 0\n", STR_LENGTH - 1);
 
     return sdp;
diff --git a/src/video_rxtx/h264_sdp.cpp b/src/video_rxtx/h264_sdp.cpp
index 4714d64c6..c0c93a58b 100644
--- a/src/video_rxtx/h264_sdp.cpp
+++ b/src/video_rxtx/h264_sdp.cpp
@@ -82,7 +82,7 @@ h264_sdp_video_rxtx::h264_sdp_video_rxtx(std::map<std::string, param_u> const &p
         }
 
         LOG(LOG_LEVEL_WARNING) << "Warning: SDP support is experimental only. Things may be broken - feel free to report them but the support may be limited.\n";
-        m_sdp = new_sdp(params.at("force_ip_version").i, m_requested_receiver.c_str());
+        m_sdp = new_sdp(rtp_is_ipv6(m_network_devices[0]) ? 6 : 4 , m_requested_receiver.c_str());
         m_saved_addr = m_requested_receiver;
         if (m_sdp == nullptr) {
                 throw string("[SDP] SDP creation failed\n");
@@ -162,6 +162,12 @@ void h264_sdp_video_rxtx::sdp_add_video(codec_t codec)
 #endif
 }
 
+/**
+ * @note
+ * This function sets compression just after first frame is received. The delayed initialization is to allow devices
+ * producing H.264/JPEG natively (eg. v4l2) to be passed untouched to transport. Fallback H.264 is applied when uncompressed
+ * stream is detected.
+ */
 void h264_sdp_video_rxtx::send_frame(shared_ptr<video_frame> tx_frame)
 {
         if (!is_codec_opaque(tx_frame->color_spec)) {