Don't use std::optional and disable c++17

Author: bjsowa

CMakeLists.txt

@@ -14,10 +14,6 @@ pkg_check_modules(avformat libavformat REQUIRED)
 pkg_check_modules(avutil libavutil REQUIRED)
 pkg_check_modules(swscale libswscale REQUIRED)
 
-if(NOT CMAKE_CXX_STANDARD)
-  set(CMAKE_CXX_STANDARD 17)
-endif()
-
 ###################################################
 ## Declare things to be passed to other projects ##
 ###################################################

include/web_video_server/libav_streamer.h

@@ -1,7 +1,7 @@
 #ifndef LIBAV_STREAMERS_H_
 #define LIBAV_STREAMERS_H_
 
-#include <optional>
+#include <chrono>
 
 #include <image_transport/image_transport.h>
 #include "web_video_server/image_streamer.h"
@@ -47,8 +47,9 @@ class LibavStreamer : public ImageTransportImageStreamer
 private:
   AVFrame* frame_;
   struct SwsContext* sws_context_;
-  std::optional<std::chrono::steady_clock::time_point> first_image_timestamp_;
   boost::mutex encode_mutex_;
+  bool first_image_received_;
+  std::chrono::steady_clock::time_point first_image_time_;
 
   std::string format_name_;
   std::string codec_name_;

src/libav_streamer.cpp

@@ -53,7 +53,7 @@ LibavStreamer::LibavStreamer(const async_web_server_cpp::HttpRequest &request,
                              const std::string &format_name, const std::string &codec_name,
                              const std::string &content_type) :
     ImageTransportImageStreamer(request, connection, nh), output_format_(0), format_context_(0), codec_(0), codec_context_(0), video_stream_(
-        0), frame_(0), sws_context_(0), first_image_timestamp_(std::nullopt), format_name_(
+        0), frame_(0), sws_context_(0), first_image_received_(false), first_image_time_(), format_name_(
         format_name), codec_name_(codec_name), content_type_(content_type), opt_(0), io_buffer_(0)
 {
 
@@ -261,8 +261,9 @@ void LibavStreamer::sendImage(
   const std::chrono::steady_clock::time_point & time)
 {
   boost::mutex::scoped_lock lock(encode_mutex_);
-  if (!first_image_timestamp_.has_value()) {
-    first_image_timestamp_ = time;
+  if (!first_image_received_) {
+    first_image_received_ = true;
+    first_image_time_ = time;
   }
   std::vector<uint8_t> encoded_frame;
 #if (LIBAVUTIL_VERSION_MAJOR < 53)
@@ -355,7 +356,7 @@ void LibavStreamer::sendImage(
     uint8_t *output_buf;
 
     double seconds = std::chrono::duration_cast<std::chrono::duration<double>>(time -
-        first_image_timestamp_.value()).count();
+        first_image_time_).count();
     // Encode video at 1/0.95 to minimize delay
     pkt.pts = (int64_t)(seconds / av_q2d(video_stream_->time_base) * 0.95);
     if (pkt.pts <= 0)