audio: add gain control to capture and playback

tests/test_audio.py

@@ -1,6 +1,8 @@
 """Tests for AudioPipeline."""
 
-from tuimble.audio import FRAME_SIZE, SAMPLE_RATE, AudioPipeline
+import struct
+
+from tuimble.audio import FRAME_SIZE, SAMPLE_RATE, AudioPipeline, _apply_gain
 
 
 def test_default_construction():
@@ -125,3 +127,79 @@ def test_stop_without_start():
     """Stop on unstarted pipeline should not raise."""
     ap = AudioPipeline()
     ap.stop()
+
+
+# -- _apply_gain tests -------------------------------------------------------
+
+
+def test_apply_gain_unity():
+    """Gain 1.0 returns identical samples."""
+    pcm = struct.pack("<4h", 100, -200, 32767, -32768)
+    assert _apply_gain(pcm, 1.0) == pcm
+
+
+def test_apply_gain_double():
+    """Gain 2.0 doubles sample values."""
+    pcm = struct.pack("<2h", 100, -100)
+    result = struct.unpack("<2h", _apply_gain(pcm, 2.0))
+    assert result == (200, -200)
+
+
+def test_apply_gain_clips():
+    """Values exceeding int16 range are clipped."""
+    pcm = struct.pack("<2h", 20000, -20000)
+    result = struct.unpack("<2h", _apply_gain(pcm, 2.0))
+    assert result == (32767, -32768)
+
+
+def test_apply_gain_zero():
+    """Gain 0.0 produces silence."""
+    pcm = struct.pack("<2h", 1000, -1000)
+    result = struct.unpack("<2h", _apply_gain(pcm, 0.0))
+    assert result == (0, 0)
+
+
+def test_apply_gain_empty():
+    """Empty buffer returns empty."""
+    assert _apply_gain(b"", 2.0) == b""
+
+
+# -- gain property tests ------------------------------------------------------
+
+
+def test_gain_defaults():
+    ap = AudioPipeline()
+    assert ap.input_gain == 1.0
+    assert ap.output_gain == 1.0
+
+
+def test_gain_clamping():
+    ap = AudioPipeline()
+    ap.input_gain = 3.0
+    assert ap.input_gain == 2.0
+    ap.output_gain = -1.0
+    assert ap.output_gain == 0.0
+
+
+def test_capture_callback_applies_input_gain():
+    """Input gain is applied to captured PCM."""
+    ap = AudioPipeline()
+    ap.capturing = True
+    ap.input_gain = 0.5
+    pcm = struct.pack("<2h", 1000, -1000)
+    ap._capture_callback(pcm, 2, None, None)
+    frame = ap.get_capture_frame()
+    result = struct.unpack("<2h", frame)
+    assert result == (500, -500)
+
+
+def test_playback_callback_applies_output_gain():
+    """Output gain is applied during playback."""
+    ap = AudioPipeline()
+    ap.output_gain = 0.5
+    pcm = struct.pack("<2h", 1000, -1000)
+    ap.queue_playback(pcm)
+    outdata = bytearray(4)
+    ap._playback_callback(outdata, 2, None, None)
+    result = struct.unpack("<2h", bytes(outdata))
+    assert result == (500, -500)