Add H.264 inference session recording and replay

include/camera.hpp

@@ -4,6 +4,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <nlohmann/json.hpp>
 
 namespace cms {
 struct CameraConfig {
@@ -13,6 +14,8 @@ struct CameraConfig {
 struct CapturedFrame {
     CaptureMetadata metadata;
     std::shared_ptr<const BgrImage> image;
+    // Present only for offline replay; keeps original timestamps and context.
+    std::shared_ptr<const nlohmann::json> replay_record;
 };
 // The capture thread exclusively owns read(); requestStop() is thread safe.
 class Camera {

include/camera_pipeline.hpp

@@ -7,8 +7,10 @@
 
 namespace cms {
 struct PipelineConfig {
+    static constexpr char const* session_variant="inference-only";
     CameraConfig camera;
     OutputOptions output;
+    std::filesystem::path record_session,replay_session;
     std::filesystem::path engines,door_mask;
     double detector_confidence{0.30};
     int max_people{3};

include/inference_session.hpp

@@ -0,0 +1,38 @@
+#pragma once
+#include "camera.hpp"
+#include "frame_result.hpp"
+#include <nlohmann/json.hpp>
+#include <filesystem>
+#include <fstream>
+#include <opencv2/videoio.hpp>
+
+namespace cms {
+struct PipelineConfig;
+// H.264/MP4 plus a matching frame index and per-frame inference records.
+// finish() flushes the encoder and marks the session replayable.
+class SessionWriter {
+public:
+    explicit SessionWriter(PipelineConfig const& config);
+    void write(FrameResult const& result, nlohmann::json const& stages,
+               nlohmann::json const* source = nullptr);
+    void finish();
+private:
+    std::filesystem::path directory_;
+    std::ofstream index_;
+    cv::VideoWriter video_;
+    int width_{},height_{};
+    std::uint64_t count_{};
+    bool finished_{};
+};
+class SessionReader {
+public:
+    explicit SessionReader(PipelineConfig& config);
+    std::optional<CapturedFrame> read();
+private:
+    std::filesystem::path directory_;
+    std::ifstream index_;
+    cv::VideoCapture video_;
+    int width_{},height_{};
+    std::uint64_t count_{},lastFrame_{},expectedCount_{};
+};
+}