conference: only create video mixer if needed

This avoids video mixer/camera access for calls with no video

Refs #45998

Change-Id: I5d1a6776a861bbd883863e02c6a02e682def4b0e

daemon/src/conference.cpp

@@ -51,7 +51,7 @@ Conference::Conference()
     , confState_(ACTIVE_ATTACHED)
     , participants_()
 #ifdef SFL_VIDEO
-    , videoMixer_(new sfl_video::VideoMixer(id_))
+    , videoMixer_(nullptr)
 #endif
 {
     Recordable::initRecFilename(id_);
@@ -184,6 +184,8 @@ std::string Conference::getConfID() const {
 #ifdef SFL_VIDEO
 std::shared_ptr<sfl_video::VideoMixer> Conference::getVideoMixer()
 {
+    if (!videoMixer_)
+        videoMixer_.reset(new sfl_video::VideoMixer(id_));
     return videoMixer_;
 }
 #endif

daemon/src/video/video_rtp_session.cpp

@@ -246,6 +246,7 @@ void VideoRtpSession::setupConferenceVideoPipeline()
 void VideoRtpSession::getMixerFromConference(Conference &conf)
 {
     std::lock_guard<std::mutex> lock(mutex_);
+    if (sending_ or receiving_)
         videoMixerSP_ = std::move(conf.getVideoMixer());
 }