Revert "Revert "Send ffmpeg stderr to /dev/null unless debug=True""

This reverts commit 5233baf451.

micmon/audio/source.py

@@ -1,8 +1,9 @@
 import logging
+import os
 import signal
 import subprocess
 from abc import ABC
-from typing import Optional, Union
+from typing import Optional, Union, IO
 
 from micmon.audio.segment import AudioSegment
 
@@ -12,7 +13,8 @@ class AudioSource(ABC):
                  sample_duration: float = 2.0,
                  sample_rate: int = 44100,
                  channels: int = 1,
-                 ffmpeg_bin: str = 'ffmpeg'):
+                 ffmpeg_bin: str = 'ffmpeg',
+                 debug: bool = False):
         self.ffmpeg_bin = ffmpeg_bin
         self.ffmpeg_base_args = (
             '-f', 's16le',
@@ -26,7 +28,10 @@ class AudioSource(ABC):
         self.sample_duration = sample_duration
         self.sample_rate = sample_rate
         self.channels = channels
+        self.debug = debug
         self.logger = logging.getLogger(self.__class__.__name__)
+        self.logger.setLevel(logging.DEBUG if self.debug else logging.INFO)
+        self.devnull: Optional[IO] = None
 
     def __iter__(self):
         return self
@@ -42,7 +47,12 @@ class AudioSource(ABC):
         raise StopIteration
 
     def __enter__(self):
-        self.ffmpeg = subprocess.Popen(self.ffmpeg_args, stdout=subprocess.PIPE)
+        kwargs = dict(stdout=subprocess.PIPE)
+        if not self.debug:
+            self.devnull = open(os.devnull, 'w')
+            kwargs['stderr'] = self.devnull
+
+        self.ffmpeg = subprocess.Popen(self.ffmpeg_args, **kwargs)
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
@@ -59,6 +69,10 @@ class AudioSource(ABC):
             self.ffmpeg.wait()
             self.ffmpeg = None
 
+        if self.devnull:
+            self.devnull.close()
+            self.devnull = None
+
     def pause(self):
         if not self.ffmpeg:
             return