Fix ffmpeg H.264 input options for older builds

Author: bonnieking

src/ac_training_lab/picam/device.py

@@ -180,9 +180,9 @@ def start_stream(ffmpeg_url, stream_key):
         "+genpts",
         "-f",
         "h264",
-        "-framerate",
+        "-r",
         "15",
-        "-video_size",
+        "-s",
         "854x480",
         "-i",
         "pipe:0",