DDS pipeline streams from sensor before opening another

src/pipeline/pipeline.cpp

@@ -9,6 +9,9 @@
 #include "media/ros/ros_writer.h"
 #include <src/proc/syncer-processing-block.h>
 #include <src/core/frame-callback.h>
+#ifdef BUILD_WITH_DDS
+#include <src/dds/rs-dds-device-proxy.h>
+#endif
 
 #include <rsutils/string/from.h>
 
@@ -127,8 +130,21 @@ namespace librealsense
             }
 
             _dispatcher.start();
-            profile->_multistream.open();
-            profile->_multistream.start(callbacks);
+#ifdef BUILD_WITH_DDS
+            if( Is< librealsense::dds_device_proxy >( dev ) )
+            {
+                // For DDS devices open() only sets requested profiles, start() actually starts streaming.
+                // Calling open() then start() sends open-streams control for all sensors before starting to stream,
+                // second open-streams control will resets the first (reverting first requested streams to defaults).
+                // open_and_start() starts streaming from the first sensor before the second open so it does not reset.
+                profile->_multistream.open_and_start( callbacks );
+            }
+            else
+#endif
+            {
+                profile->_multistream.open();
+                profile->_multistream.start( callbacks );
+            }
             _active_profile = profile;
             _prev_conf = std::make_shared<config>(*conf);
         }

src/pipeline/resolver.h

@@ -157,6 +157,19 @@ namespace librealsense
                         sensor.second->start(callback);
                 }
 
+                template< class T >
+                void open_and_start( T callback )
+                {
+                    // Calling open() than start() opens all relevant sensors before starting any of them.
+                    // For some device backends we want to open and start each sensor before opening the next sensor.
+                    for( auto it = _dev_to_profiles.rbegin(); it != _dev_to_profiles.rend(); it++ )
+                    {
+                        auto && sub = _results.at( it->first );
+                        sub->open( it->second );
+                        sub->start( callback );
+                    }
+                }
+
                 void stop()
                 {
                     for (auto&& sensor : _results)