From 321995944e46e187ee515d358f137d94c30f090e Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Fri, 14 Apr 2017 01:04:32 +0200
Subject: [PATCH] Add a Lua function to rewind the video.

---
 ffmpeg_capture.cpp | 16 ++++++++++++++++
 ffmpeg_capture.h   | 13 +++++++++++++
 theme.cpp          |  9 +++++++++
 3 files changed, 38 insertions(+)

diff --git a/ffmpeg_capture.cpp b/ffmpeg_capture.cpp
index 647b7cb..bb41a35 100644
--- a/ffmpeg_capture.cpp
+++ b/ffmpeg_capture.cpp
@@ -186,6 +186,22 @@ bool FFmpegCapture::play_video(const string &pathname)
 
 	// Main loop.
 	while (!producer_thread_should_quit) {
+		// Process any queued commands from other threads.
+		vector<QueuedCommand> commands;
+		{
+			lock_guard<mutex> lock(queue_mu);
+			swap(commands, command_queue);
+		}
+		for (const QueuedCommand &cmd : commands) {
+			if (cmd.command == QueuedCommand::REWIND) {
+				if (av_seek_frame(format_ctx.get(), /*stream_index=*/-1, /*timestamp=*/0, /*flags=*/0) < 0) {
+					fprintf(stderr, "%s: Rewind failed, stopping play.\n", pathname.c_str());
+				}
+				start = steady_clock::now();
+				continue;
+			}
+		}
+
 		// Read packets until we have a frame or there are none left.
 		int frame_finished = 0;
 		AVFrameWithDeleter frame = av_frame_alloc_unique();
diff --git a/ffmpeg_capture.h b/ffmpeg_capture.h
index 8c75b4f..daf353e 100644
--- a/ffmpeg_capture.h
+++ b/ffmpeg_capture.h
@@ -26,6 +26,7 @@
 #include <functional>
 #include <map>
 #include <memory>
+#include <mutex>
 #include <set>
 #include <string>
 #include <thread>
@@ -48,6 +49,12 @@ public:
 		return card_index;
 	}
 
+	void rewind()
+	{
+		std::lock_guard<std::mutex> lock(queue_mu);
+		command_queue.push_back(QueuedCommand { QueuedCommand::REWIND });
+	}
+
 	// CaptureInterface.
 	void set_video_frame_allocator(bmusb::FrameAllocator *allocator) override
 	{
@@ -147,6 +154,12 @@ private:
 
 	std::atomic<bool> producer_thread_should_quit{false};
 	std::thread producer_thread;
+
+	std::mutex queue_mu;
+	struct QueuedCommand {
+		enum Command { REWIND } command;
+	};
+	std::vector<QueuedCommand> command_queue;  // Protected by <queue_mu>.
 };
 
 #endif  // !defined(_FFMPEG_CAPTURE_H)
diff --git a/theme.cpp b/theme.cpp
index 46803ba..7ece56a 100644
--- a/theme.cpp
+++ b/theme.cpp
@@ -352,6 +352,14 @@ int VideoInput_new(lua_State* L)
 	return ret;
 }
 
+int VideoInput_rewind(lua_State* L)
+{
+	assert(lua_gettop(L) == 1);
+	FFmpegCapture **video_input = (FFmpegCapture **)luaL_checkudata(L, 1, "VideoInput");
+	(*video_input)->rewind();
+	return 0;
+}
+
 int WhiteBalanceEffect_new(lua_State* L)
 {
 	assert(lua_gettop(L) == 0);
@@ -553,6 +561,7 @@ const luaL_Reg ImageInput_funcs[] = {
 
 const luaL_Reg VideoInput_funcs[] = {
 	{ "new", VideoInput_new },
+	{ "rewind", VideoInput_rewind },
 	{ NULL, NULL }
 };
 
-- 
2.39.2