[Refactor] Remove dependency on librosa (#2273)

Signed-off-by: Nick Cao <ncao@redhat.com>
Co-authored-by: Claude <noreply@anthropic.com>

tests/entrypoints/openai_api/test_serving_speech.py

@@ -63,14 +63,11 @@ class TestAudioMixin:
         adjusted_tensor = mock_speed.call_args[0][0]
         assert len(adjusted_tensor) == 24000
 
-    def test_speed_adjustment(self, audio_mixin, mocker: MockerFixture):
-        mock_time_stretch = mocker.patch("librosa.effects.time_stretch")
-        mock_time_stretch.return_value = np.zeros(12000)
+    def test_speed_adjustment(self, audio_mixin):
         audio_tensor = np.random.rand(24000).astype(np.float32)
 
         adjusted_audio, _ = audio_mixin._apply_speed_adjustment(audio_tensor, speed=2.0, sample_rate=24000)
 
-        mock_time_stretch.assert_called_with(y=audio_tensor, rate=2.0)
         assert adjusted_audio.shape == (12000,)
 
     def test_unsupported_format_fallback(self, audio_mixin, caplog, mocker: MockerFixture):
@@ -117,30 +114,22 @@ class TestAudioMixin:
         assert np.array_equal(output_tensor, stereo_tensor)
 
     def test_speed_adjustment_bypass(self, audio_mixin, mocker: MockerFixture):
-        """Test that speed=1.0 bypasses the expensive librosa time stretching."""
+        """Test that speed=1.0 bypasses the expensive torchaudio time stretching."""
         audio_tensor = np.random.rand(24000).astype(np.float32)
 
-        mock_time_stretch = mocker.patch("librosa.effects.time_stretch")
-        # speed=1.0 should return immediately without calling librosa
+        mock_time_stretch = mocker.patch("torchaudio.transforms.TimeStretch")
+        # speed=1.0 should return immediately without calling torchaudio
         result, _ = audio_mixin._apply_speed_adjustment(audio_tensor, speed=1.0, sample_rate=24000)
 
         mock_time_stretch.assert_not_called()
         assert np.array_equal(result, audio_tensor)
 
-    def test_speed_adjustment_stereo_handling(self, audio_mixin, mocker: MockerFixture):
-        """Test that speed adjustment is attempted on stereo inputs."""
-        mock_time_stretch = mocker.patch("librosa.effects.time_stretch")
+    def test_speed_adjustment_stereo_handling(self, audio_mixin):
+        """Test that speed adjustment handles stereo (channels-last) input."""
         stereo_tensor = np.random.rand(24000, 2).astype(np.float32)
-        # Mock return value representing a sped-up version (half length)
-        mock_time_stretch.return_value = np.zeros((12000, 2), dtype=np.float32)
 
         result, _ = audio_mixin._apply_speed_adjustment(stereo_tensor, speed=2.0, sample_rate=24000)
 
-        mock_time_stretch.assert_called_once()
-        # Ensure the stereo tensor was passed to librosa
-        call_args = mock_time_stretch.call_args
-        assert np.array_equal(call_args.kwargs["y"], stereo_tensor)
-        assert call_args.kwargs["rate"] == 2.0
         assert result.shape == (12000, 2)