Currently we get video info from youtube-dl twice. Once to get the video URL to ffprobe it for FPS before processing the video. Proof of concept diff to calculate FPS as part of the processing. Improves time to first LED light by a few seconds: https://gist.github.com/dasl-/9c0e6eb3912e17d82cb923aa92282f14

fps.diff

  diff --git a/lightness/videoprocessor.py b/lightness/videoprocessor.py
index 7a75480..d6d7615 100644
--- a/lightness/videoprocessor.py
+++ b/lightness/videoprocessor.py
@@ -100,11 +100,12 @@ class VideoProcessor:
     def __process_and_play_video(self, video_player):
         self.__do_pre_cleanup()
 
-        fps = self.__calculate_fps()
+        # fps = self.__calculate_fps()
         ffmpeg_to_python_fifo_name = self.__make_ffmpeg_to_python_fifo()
+        ffprobe_to_python_fifo_name = self.__make_ffmpeg_to_python_fifo()
         self.__maybe_set_volume()
 
-        process_and_play_vid_cmd = self.__get_process_and_play_vid_cmd(ffmpeg_to_python_fifo_name)
+        process_and_play_vid_cmd = self.__get_process_and_play_vid_cmd(ffmpeg_to_python_fifo_name, ffprobe_to_python_fifo_name)
         self.__logger.info('executing process and play cmd: ' + process_and_play_vid_cmd)
         process_and_play_vid_proc = subprocess.Popen(process_and_play_vid_cmd, shell = True, executable = '/bin/bash')
 
@@ -116,12 +117,26 @@ class VideoProcessor:
             bytes_per_frame = bytes_per_frame * 3
             np_array_shape.append(3)
 
+        ffprobe_to_python_fifo = open(ffprobe_to_python_fifo_name, 'rb')
+        while True:
+            is_ready_to_read, ignore1, ignore2 = select.select([ffprobe_to_python_fifo], [], [], 0)
+            if not is_ready_to_read:
+                continue
+
+            fps_parts = ffprobe_to_python_fifo.readline().decode("utf-8")
+            fps_parts = fps_parts.split('/')
+            fps = float(fps_parts[0]) / float(fps_parts[1])
+            break
+
         start_time = None
         frame_length =  1 / fps
         last_frame = None
         is_ffmpeg_done_outputting = False
         avg_color_frames = ReadOnceCircularBuffer(self.__FRAMES_BUFFER_LENGTH)
         ffmpeg_to_python_fifo = open(ffmpeg_to_python_fifo_name, 'rb')
+
+
+
         while True:
             if is_ffmpeg_done_outputting or avg_color_frames.is_full():
                 pass
@@ -194,7 +209,7 @@ class VideoProcessor:
         video_player.playFrame(avg_color_frames[cur_frame])
         return [False, cur_frame]
 
-    def __get_process_and_play_vid_cmd(self, ffmpeg_to_python_fifo_name):
+    def __get_process_and_play_vid_cmd(self, ffmpeg_to_python_fifo_name, ffprobe_to_python_fifo_name):
         video_save_path = self.__get_video_save_path()
         vid_data_cmd = None
         if self.__is_video_already_downloaded:
@@ -222,6 +237,7 @@ class VideoProcessor:
         process_and_play_vid_cmd = (
             'set -o pipefail && ' +
             vid_data_cmd + "tee " +
+            ">(ffprobe -i pipe:0 -v 0 -of csv=p=0 -select_streams v:0 -show_entries stream=r_frame_rate > " + ffprobe_to_python_fifo_name + " 2>/dev/null; cat >/dev/null) " +
             maybe_play_audio_tee +
             ">(" + self.__get_ffmpeg_cmd() + " > " + ffmpeg_to_python_fifo_name + ") " +
             maybe_save_video_tee +
@@ -231,12 +247,13 @@ class VideoProcessor:
         return process_and_play_vid_cmd
 
     def __get_youtube_dl_cmd(self):
-        video_info = self.__get_video_info()
+        # video_info = self.__get_video_info()
         return (
             'youtube-dl ' +
             '--output - ' + # output to stdout
-            '--format ' + shlex.quote(video_info['format_id']) + " " + # download the specified video quality / encoding
-            shlex.quote(video_info['webpage_url']) # url to download
+            '--format ' + self.__YOUTUBE_DL_FORMAT + ' ' +
+            # '--format ' + shlex.quote(video_info['format_id']) + " " + # download the specified video quality / encoding
+            shlex.quote(self.__url) # url to download
         )
 
     def __get_ffmpeg_cmd(self):