From dd7789d6d360ede408bec22f0f15c47fb08982df Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Fri, 14 Dec 2018 20:15:06 +0100
Subject: [PATCH] Make Futatabi output frame rate adjustable.

---
 futatabi/flags.cpp  | 17 ++++++++++++++++-
 futatabi/flags.h    |  1 +
 futatabi/player.cpp |  7 +++----
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/futatabi/flags.cpp b/futatabi/flags.cpp
index 11ae71d..7a82460 100644
--- a/futatabi/flags.cpp
+++ b/futatabi/flags.cpp
@@ -25,6 +25,8 @@ void usage()
 	fprintf(stderr, "      --help                      print usage information\n");
 	fprintf(stderr, "  -w, --width                     output width in pixels (default 1280)\n");
 	fprintf(stderr, "  -h, --height                    output height in pixels (default 720)\n");
+	fprintf(stderr, "  -r, --frame-rate NUM[/NUM]      output frame rate, as a float or fraction\n");
+	fprintf(stderr, "                                    (default 60000/1001 ~= 59.94)\n");
 	fprintf(stderr, "      --slow-down-input           slow down input to realtime (default on if no\n");
 	fprintf(stderr, "                                    source URL given)\n");
 	fprintf(stderr, "  -q, --interpolation-quality N   0 = off\n");
@@ -42,6 +44,7 @@ void parse_flags(int argc, char * const argv[])
 		{ "help", no_argument, 0, OPTION_HELP },
 		{ "width", required_argument, 0, 'w' },
 		{ "height", required_argument, 0, 'h' },
+		{ "frame-rate", required_argument, 0, 'r' },
 		{ "slow-down-input", no_argument, 0, OPTION_SLOW_DOWN_INPUT },
 		{ "interpolation-quality", required_argument, 0, 'q' },
 		{ "working-directory", required_argument, 0, 'd' },
@@ -50,7 +53,7 @@ void parse_flags(int argc, char * const argv[])
 	};
 	for ( ;; ) {
 		int option_index = 0;
-		int c = getopt_long(argc, argv, "w:h:q:d:", long_options, &option_index);
+		int c = getopt_long(argc, argv, "w:h:r:q:d:", long_options, &option_index);
 
 		if (c == -1) {
 			break;
@@ -62,6 +65,18 @@ void parse_flags(int argc, char * const argv[])
 		case 'h':
 			global_flags.height = atoi(optarg);
 			break;
+		case 'r': {
+			double num, den;
+			if (sscanf(optarg, "%lf/%lf", &num, &den) == 2) {
+				global_flags.output_framerate = num / den;
+			} else if (sscanf(optarg, "%lf", &num) == 1) {
+				global_flags.output_framerate = num;
+			} else {
+				fprintf(stderr, "Invalid frame rate given (must be on the form N or N/M)\n");
+				exit(1);
+			}
+			break;
+		}
 		case OPTION_SLOW_DOWN_INPUT:
 			global_flags.slow_down_input = true;
 			break;
diff --git a/futatabi/flags.h b/futatabi/flags.h
index 3950936..23be12c 100644
--- a/futatabi/flags.h
+++ b/futatabi/flags.h
@@ -12,6 +12,7 @@ struct Flags {
 	bool slow_down_input = false;
 	int interpolation_quality = 2;
 	uint16_t http_port = DEFAULT_HTTPD_PORT;
+	double output_framerate = 60000.0 / 1001.0;
 };
 extern Flags global_flags;
 
diff --git a/futatabi/player.cpp b/futatabi/player.cpp
index 80e77d1..2fb3939 100644
--- a/futatabi/player.cpp
+++ b/futatabi/player.cpp
@@ -47,7 +47,6 @@ void Player::thread_func(Player::StreamOutput stream_output, AVFormatContext *fi
 
 	check_error();
 
-	constexpr double output_framerate = 60000.0 / 1001.0;  // FIXME: make configurable
 	int64_t pts = 0;
 	Clip next_clip;
 	size_t next_clip_idx = size_t(-1);
@@ -115,10 +114,10 @@ got_clip:
 		int64_t in_pts_start_next_clip = -1;
 		steady_clock::time_point next_frame_start;
 		for (int frameno = 0; !should_quit; ++frameno) {  // Ends when the clip ends.
-			double out_pts = out_pts_origin + TIMEBASE * frameno / output_framerate;
+			double out_pts = out_pts_origin + TIMEBASE * frameno / global_flags.output_framerate;
 			next_frame_start =
 				origin + microseconds(lrint((out_pts - out_pts_origin) * 1e6 / TIMEBASE));
-			int64_t in_pts = lrint(in_pts_origin + TIMEBASE * frameno * speed / output_framerate);
+			int64_t in_pts = lrint(in_pts_origin + TIMEBASE * frameno * speed / global_flags.output_framerate);
 			pts = lrint(out_pts);
 
 			if (in_pts >= clip.pts_out) {
@@ -264,7 +263,7 @@ got_clip:
 			// TODO: Snap secondary (fade-to) clips in the same fashion.
 			bool snapped = false;
 			for (FrameOnDisk snap_frame : { frame_lower, frame_upper }) {
-				double snap_pts_as_frameno = (snap_frame.pts - in_pts_origin) * output_framerate / TIMEBASE / speed;
+				double snap_pts_as_frameno = (snap_frame.pts - in_pts_origin) * global_flags.output_framerate / TIMEBASE / speed;
 				if (fabs(snap_pts_as_frameno - frameno) < 0.01) {
 					auto display_func = [this, primary_stream_idx, snap_frame, secondary_frame, fade_alpha]{
 						if (destination != nullptr) {
-- 
2.39.2