Add FFmpeg input buffering

ovgenpy/outputs.py

@@ -11,6 +11,7 @@ if TYPE_CHECKING:
 
 
 RGB_DEPTH = 3
+FRAMES_TO_BUFFER = 2
 
 
 class IOutputConfig:
@@ -25,6 +26,11 @@ class Output(ABC):
         self.ovgen_cfg = ovgen_cfg
         self.cfg = cfg
 
+        rcfg = ovgen_cfg.render
+
+        frame_bytes = rcfg.height * rcfg.width * RGB_DEPTH
+        self.bufsize = frame_bytes * FRAMES_TO_BUFFER
+
     @abstractmethod
     def write_frame(self, frame: bytes) -> None:
         """ Output a Numpy ndarray. """
@@ -57,12 +63,9 @@ class _FFmpegCommand:
         if self.ovgen_cfg.master_audio:
             self.templates.append(cfg.audio_template)  # audio
 
-    def popen(self, process_args=None, **kwargs) -> subprocess.Popen:
-        if process_args is None:
-            process_args = []
-
-        return subprocess.Popen(self._generate_args() + process_args,
-                                stdin=subprocess.PIPE, **kwargs)
+    def popen(self, extra_args, bufsize, **kwargs) -> subprocess.Popen:
+        return subprocess.Popen(self._generate_args() + extra_args,
+                                stdin=subprocess.PIPE, bufsize=bufsize, **kwargs)
 
     def _generate_args(self) -> List[str]:
         return [arg
@@ -121,7 +124,7 @@ class FFmpegOutput(ProcessOutput):
 
         ffmpeg = _FFmpegCommand([FFMPEG, '-y'], ovgen_cfg)
         ffmpeg.add_output(cfg)
-        self.open(ffmpeg.popen([cfg.path]))
+        self.open(ffmpeg.popen([cfg.path], self.bufsize))
 
 
 # FFplayOutput
@@ -140,9 +143,9 @@ class FFplayOutput(ProcessOutput):
 
         ffmpeg = _FFmpegCommand([FFMPEG], ovgen_cfg)
         ffmpeg.add_output(cfg)
-        ffmpeg.templates.append('-f nut -')
+        ffmpeg.templates.append('-f nut')
 
-        p1 = ffmpeg.popen(stdout=subprocess.PIPE)
+        p1 = ffmpeg.popen(['-'], self.bufsize, stdout=subprocess.PIPE)
 
         ffplay = shlex.split('ffplay -autoexit -')
         self.p2 = subprocess.Popen(ffplay, stdin=p1.stdout)