perf: ALSA ffmpeg low-delay flags

nobuffer, low_delay, and a small thread_queue_size on the camera
mic capture process.

run_worker.py

@@ -179,6 +179,8 @@ def main() -> int:
 
             aproc = subprocess.Popen(
                 ["ffmpeg", "-hide_banner", "-loglevel", "error",
+                 "-fflags", "nobuffer", "-flags", "low_delay",
+                 "-thread_queue_size", "64",
                  "-f", "alsa", "-i", f"hw:{audio_card},0",
                  "-ar", str(args.audio_rate), "-ac", "2",
                  "-f", "s16le", "pipe:1"],

tests/test_run_worker_ffmpeg.py

@@ -0,0 +1,10 @@
+import inspect
+
+import run_worker
+
+
+def test_alsa_ffmpeg_uses_low_delay_flags():
+    src = inspect.getsource(run_worker)
+    assert '"-fflags", "nobuffer"' in src
+    assert '"-flags", "low_delay"' in src
+    assert '"-thread_queue_size", "64"' in src