diff --git a/audio/effect/6.0/IDownmixEffect.hal b/audio/effect/6.0/IDownmixEffect.hal
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+++ b/audio/effect/6.0/IDownmixEffect.hal
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+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.hardware.audio.effect@6.0;
+
+import android.hardware.audio.common@6.0;
+import IEffect;
+
+interface IDownmixEffect extends IEffect {
+    enum Type : int32_t {
+        STRIP, // throw away the extra channels
+        FOLD   // mix the extra channels with FL/FR
+    };
+
+    /**
+     * Sets the current downmix preset.
+     */
+    setType(Type preset) generates (Result retval);
+
+    /**
+     * Gets the current downmix preset.
+     */
+    getType() generates (Result retval, Type preset);
+};