diff --git a/audio/aidl/Android.bp b/audio/aidl/Android.bp
index d4c9a65..7d474b2 100644
--- a/audio/aidl/Android.bp
+++ b/audio/aidl/Android.bp
@@ -41,6 +41,7 @@
         "android/hardware/audio/common/SinkMetadata.aidl",
         "android/hardware/audio/common/SourceMetadata.aidl",
     ],
+    frozen: true,
     imports: [
         "android.media.audio.common.types-V2",
     ],
@@ -131,6 +132,7 @@
         "android.hardware.common-V2",
         "android.hardware.common.fmq-V1",
         "android.hardware.audio.common-V1",
+        "android.hardware.audio.effect-V1",
         "android.media.audio.common.types-V2",
     ],
     backend: {
diff --git a/audio/aidl/TEST_MAPPING b/audio/aidl/TEST_MAPPING
index ed2cea2..3c58324 100644
--- a/audio/aidl/TEST_MAPPING
+++ b/audio/aidl/TEST_MAPPING
@@ -10,6 +10,9 @@
       "name": "VtsHalAudioEffectTargetTest"
     },
     {
+      "name": "VtsHalDownmixTargetTest"
+    },
+    {
       "name": "VtsHalEqualizerTargetTest"
     },
     {
diff --git a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IModule.aidl b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IModule.aidl
index ebfa94b..dd2279d 100644
--- a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IModule.aidl
+++ b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IModule.aidl
@@ -64,6 +64,8 @@
   int generateHwAvSyncId();
   android.hardware.audio.core.VendorParameter[] getVendorParameters(in @utf8InCpp String[] ids);
   void setVendorParameters(in android.hardware.audio.core.VendorParameter[] parameters, boolean async);
+  void addDeviceEffect(int portConfigId, in android.hardware.audio.effect.IEffect effect);
+  void removeDeviceEffect(int portConfigId, in android.hardware.audio.effect.IEffect effect);
   @VintfStability
   parcelable OpenInputStreamArguments {
     int portConfigId;
diff --git a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IStreamCommon.aidl b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IStreamCommon.aidl
index 8471c79..f0bf100 100644
--- a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IStreamCommon.aidl
+++ b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/IStreamCommon.aidl
@@ -38,4 +38,6 @@
   void updateHwAvSyncId(int hwAvSyncId);
   android.hardware.audio.core.VendorParameter[] getVendorParameters(in @utf8InCpp String[] ids);
   void setVendorParameters(in android.hardware.audio.core.VendorParameter[] parameters, boolean async);
+  void addEffect(in android.hardware.audio.effect.IEffect effect);
+  void removeEffect(in android.hardware.audio.effect.IEffect effect);
 }
diff --git a/audio/aidl/android/hardware/audio/core/IModule.aidl b/audio/aidl/android/hardware/audio/core/IModule.aidl
index 7facc6c..b278ac4 100644
--- a/audio/aidl/android/hardware/audio/core/IModule.aidl
+++ b/audio/aidl/android/hardware/audio/core/IModule.aidl
@@ -30,6 +30,7 @@
 import android.hardware.audio.core.ModuleDebug;
 import android.hardware.audio.core.StreamDescriptor;
 import android.hardware.audio.core.VendorParameter;
+import android.hardware.audio.effect.IEffect;
 import android.media.audio.common.AudioOffloadInfo;
 import android.media.audio.common.AudioPort;
 import android.media.audio.common.AudioPortConfig;
@@ -515,7 +516,8 @@
      * @throws EX_ILLEGAL_ARGUMENT If the port config can not be found by the ID.
      * @throws EX_ILLEGAL_STATE In the following cases:
      *                          - If the port config has a stream opened on it;
-     *                          - If the port config is used by a patch.
+     *                          - If the port config is used by a patch;
+     *                          - If the port config has an audio effect on it.
      */
     void resetAudioPortConfig(int portConfigId);
 
@@ -728,4 +730,34 @@
      * @throws EX_UNSUPPORTED_OPERATION If the module does not support vendor parameters.
      */
     void setVendorParameters(in VendorParameter[] parameters, boolean async);
+
+    /**
+     * Apply an audio effect to a device port.
+     *
+     * The audio effect applies to all audio input or output on the specific
+     * configuration of the device audio port. The effect is inserted according
+     * to its insertion preference specified by the 'flags.insert' field of the
+     * EffectDescriptor.
+     *
+     * @param portConfigId The ID of the audio port config.
+     * @param effect The effect instance.
+     * @throws EX_ILLEGAL_ARGUMENT If the device port config can not be found by the ID,
+     *                             or the effect reference is invalid.
+     * @throws EX_UNSUPPORTED_OPERATION If the module does not support device port effects.
+     */
+    void addDeviceEffect(int portConfigId, in IEffect effect);
+
+    /**
+     * Stop applying an audio effect to a device port.
+     *
+     * Undo the action of the 'addDeviceEffect' method.
+     *
+     * @param portConfigId The ID of the audio port config.
+     * @param effect The effect instance.
+     * @throws EX_ILLEGAL_ARGUMENT If the device port config can not be found by the ID,
+     *                             or the effect reference is invalid, or the effect is
+     *                             not currently applied to the port config.
+     * @throws EX_UNSUPPORTED_OPERATION If the module does not support device port effects.
+     */
+    void removeDeviceEffect(int portConfigId, in IEffect effect);
 }
diff --git a/audio/aidl/android/hardware/audio/core/IStreamCommon.aidl b/audio/aidl/android/hardware/audio/core/IStreamCommon.aidl
index 84f7309..533ef67 100644
--- a/audio/aidl/android/hardware/audio/core/IStreamCommon.aidl
+++ b/audio/aidl/android/hardware/audio/core/IStreamCommon.aidl
@@ -17,6 +17,7 @@
 package android.hardware.audio.core;
 
 import android.hardware.audio.core.VendorParameter;
+import android.hardware.audio.effect.IEffect;
 
 /**
  * This interface contains operations that are common to input and output
@@ -86,4 +87,30 @@
      * @throws EX_UNSUPPORTED_OPERATION If the stream does not support vendor parameters.
      */
     void setVendorParameters(in VendorParameter[] parameters, boolean async);
+
+    /**
+     * Apply an audio effect to the stream.
+     *
+     * This method is intended for the cases when the effect has an offload
+     * implementation, since software effects can be applied at the client side.
+     *
+     * @param effect The effect instance.
+     * @throws EX_ILLEGAL_ARGUMENT If the effect reference is invalid.
+     * @throws EX_ILLEGAL_STATE If the stream is closed.
+     * @throws EX_UNSUPPORTED_OPERATION If the module does not support audio effects.
+     */
+    void addEffect(in IEffect effect);
+
+    /**
+     * Stop applying an audio effect to the stream.
+     *
+     * Undo the action of the 'addEffect' method.
+     *
+     * @param effect The effect instance.
+     * @throws EX_ILLEGAL_ARGUMENT If the effect reference is invalid, or the effect is
+     *                             not currently applied to the stream.
+     * @throws EX_ILLEGAL_STATE If the stream is closed.
+     * @throws EX_UNSUPPORTED_OPERATION If the module does not support audio effects.
+     */
+    void removeEffect(in IEffect effect);
 }
diff --git a/audio/aidl/default/Android.bp b/audio/aidl/default/Android.bp
index a7a515a..a938551 100644
--- a/audio/aidl/default/Android.bp
+++ b/audio/aidl/default/Android.bp
@@ -151,6 +151,7 @@
     shared_libs: [
         "libbassboostsw",
         "libbundleaidl",
+        "libdownmixaidl",
         "libdynamicsprocessingsw",
         "libenvreverbsw",
         "libequalizersw",
diff --git a/audio/aidl/default/Module.cpp b/audio/aidl/default/Module.cpp
index d52e328..4a424bd 100644
--- a/audio/aidl/default/Module.cpp
+++ b/audio/aidl/default/Module.cpp
@@ -969,4 +969,28 @@
     return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
 }
 
+ndk::ScopedAStatus Module::addDeviceEffect(
+        int32_t in_portConfigId,
+        const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect) {
+    if (in_effect == nullptr) {
+        LOG(DEBUG) << __func__ << ": port id " << in_portConfigId << ", null effect";
+    } else {
+        LOG(DEBUG) << __func__ << ": port id " << in_portConfigId << ", effect Binder "
+                   << in_effect->asBinder().get();
+    }
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+ndk::ScopedAStatus Module::removeDeviceEffect(
+        int32_t in_portConfigId,
+        const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect) {
+    if (in_effect == nullptr) {
+        LOG(DEBUG) << __func__ << ": port id " << in_portConfigId << ", null effect";
+    } else {
+        LOG(DEBUG) << __func__ << ": port id " << in_portConfigId << ", effect Binder "
+                   << in_effect->asBinder().get();
+    }
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
 }  // namespace aidl::android::hardware::audio::core
diff --git a/audio/aidl/default/Stream.cpp b/audio/aidl/default/Stream.cpp
index e984091..bb123a2 100644
--- a/audio/aidl/default/Stream.cpp
+++ b/audio/aidl/default/Stream.cpp
@@ -541,6 +541,28 @@
 }
 
 template <class Metadata, class StreamWorker>
+ndk::ScopedAStatus StreamCommonImpl<Metadata, StreamWorker>::addEffect(
+        const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect) {
+    if (in_effect == nullptr) {
+        LOG(DEBUG) << __func__ << ": null effect";
+    } else {
+        LOG(DEBUG) << __func__ << ": effect Binder" << in_effect->asBinder().get();
+    }
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+template <class Metadata, class StreamWorker>
+ndk::ScopedAStatus StreamCommonImpl<Metadata, StreamWorker>::removeEffect(
+        const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect) {
+    if (in_effect == nullptr) {
+        LOG(DEBUG) << __func__ << ": null effect";
+    } else {
+        LOG(DEBUG) << __func__ << ": effect Binder" << in_effect->asBinder().get();
+    }
+    return ndk::ScopedAStatus::fromExceptionCode(EX_UNSUPPORTED_OPERATION);
+}
+
+template <class Metadata, class StreamWorker>
 ndk::ScopedAStatus StreamCommonImpl<Metadata, StreamWorker>::close() {
     LOG(DEBUG) << __func__;
     if (!isClosed()) {
diff --git a/audio/aidl/default/audio_effects_config.xml b/audio/aidl/default/audio_effects_config.xml
index c33ebf5..9491bc3 100644
--- a/audio/aidl/default/audio_effects_config.xml
+++ b/audio/aidl/default/audio_effects_config.xml
@@ -30,6 +30,7 @@
     <libraries>
         <library name="bassboostsw" path="libbassboostsw.so"/>
         <library name="bundle" path="libbundleaidl.so"/>
+        <library name="downmix" path="libdownmixaidl.so"/>
         <library name="dynamics_processingsw" path="libdynamicsprocessingsw.so"/>
         <library name="equalizersw" path="libequalizersw.so"/>
         <library name="haptic_generatorsw" path="libhapticgeneratorsw.so"/>
@@ -65,6 +66,7 @@
             <libsw library="bassboostsw" uuid="fa8181f2-588b-11ed-9b6a-0242ac120002"/>
             <libsw library="bundle" uuid="8631f300-72e2-11df-b57e-0002a5d5c51b"/>
         </effectProxy>
+        <effect name="downmix" library="downmix" uuid="93f04452-e4fe-41cc-91f9-e475b6d1d69f"/>
         <effect name="dynamics_processing" library="dynamics_processingsw" uuid="fa818d78-588b-11ed-9b6a-0242ac120002"/>
         <effect name="haptic_generator" library="haptic_generatorsw" uuid="fa819110-588b-11ed-9b6a-0242ac120002"/>
         <effect name="loudness_enhancer" library="loudness_enhancer" uuid="fa415329-2034-4bea-b5dc-5b381c8d1e2c"/>
diff --git a/audio/aidl/default/downmix/Android.bp b/audio/aidl/default/downmix/Android.bp
new file mode 100644
index 0000000..230b2d8
--- /dev/null
+++ b/audio/aidl/default/downmix/Android.bp
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2022 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 {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "hardware_interfaces_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["hardware_interfaces_license"],
+}
+
+cc_library_shared {
+    name: "libdownmixsw",
+    defaults: [
+        "aidlaudioeffectservice_defaults",
+        "latest_android_media_audio_common_types_ndk_shared",
+        "latest_android_hardware_audio_effect_ndk_shared",
+    ],
+    srcs: [
+        "DownmixSw.cpp",
+        ":effectCommonFile",
+    ],
+    visibility: [
+        "//hardware/interfaces/audio/aidl/default",
+    ],
+}
diff --git a/audio/aidl/default/downmix/DownmixSw.cpp b/audio/aidl/default/downmix/DownmixSw.cpp
new file mode 100644
index 0000000..7bb958d
--- /dev/null
+++ b/audio/aidl/default/downmix/DownmixSw.cpp
@@ -0,0 +1,170 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#include <cstddef>
+#define LOG_TAG "AHAL_DownmixSw"
+#include <Utils.h>
+#include <algorithm>
+#include <unordered_set>
+
+#include <android-base/logging.h>
+#include <fmq/AidlMessageQueue.h>
+
+#include "DownmixSw.h"
+
+using aidl::android::hardware::audio::effect::Descriptor;
+using aidl::android::hardware::audio::effect::DownmixSw;
+using aidl::android::hardware::audio::effect::IEffect;
+using aidl::android::hardware::audio::effect::kDownmixSwImplUUID;
+using aidl::android::hardware::audio::effect::State;
+using aidl::android::media::audio::common::AudioUuid;
+
+extern "C" binder_exception_t createEffect(const AudioUuid* in_impl_uuid,
+                                           std::shared_ptr<IEffect>* instanceSpp) {
+    if (!in_impl_uuid || *in_impl_uuid != kDownmixSwImplUUID) {
+        LOG(ERROR) << __func__ << "uuid not supported";
+        return EX_ILLEGAL_ARGUMENT;
+    }
+    if (instanceSpp) {
+        *instanceSpp = ndk::SharedRefBase::make<DownmixSw>();
+        LOG(DEBUG) << __func__ << " instance " << instanceSpp->get() << " created";
+        return EX_NONE;
+    } else {
+        LOG(ERROR) << __func__ << " invalid input parameter!";
+        return EX_ILLEGAL_ARGUMENT;
+    }
+}
+
+extern "C" binder_exception_t queryEffect(const AudioUuid* in_impl_uuid, Descriptor* _aidl_return) {
+    if (!in_impl_uuid || *in_impl_uuid != kDownmixSwImplUUID) {
+        LOG(ERROR) << __func__ << "uuid not supported";
+        return EX_ILLEGAL_ARGUMENT;
+    }
+    *_aidl_return = DownmixSw::kDescriptor;
+    return EX_NONE;
+}
+
+namespace aidl::android::hardware::audio::effect {
+
+const std::string DownmixSw::kEffectName = "DownmixSw";
+const Downmix::Capability DownmixSw::kCapability;
+const Descriptor DownmixSw::kDescriptor = {
+        .common = {.id = {.type = kDownmixTypeUUID,
+                          .uuid = kDownmixSwImplUUID,
+                          .proxy = std::nullopt},
+                   .flags = {.type = Flags::Type::INSERT,
+                             .insert = Flags::Insert::FIRST,
+                             .volume = Flags::Volume::CTRL},
+                   .name = kEffectName,
+                   .implementor = "The Android Open Source Project"},
+        .capability = Capability::make<Capability::downmix>(kCapability)};
+
+ndk::ScopedAStatus DownmixSw::getDescriptor(Descriptor* _aidl_return) {
+    LOG(DEBUG) << __func__ << kDescriptor.toString();
+    *_aidl_return = kDescriptor;
+    return ndk::ScopedAStatus::ok();
+}
+
+ndk::ScopedAStatus DownmixSw::setParameterSpecific(const Parameter::Specific& specific) {
+    RETURN_IF(Parameter::Specific::downmix != specific.getTag(), EX_ILLEGAL_ARGUMENT,
+              "EffectNotSupported");
+    RETURN_IF(!mContext, EX_NULL_POINTER, "nullContext");
+
+    auto& dmParam = specific.get<Parameter::Specific::downmix>();
+    auto tag = dmParam.getTag();
+
+    switch (tag) {
+        case Downmix::type: {
+            RETURN_IF(mContext->setDmType(dmParam.get<Downmix::type>()) != RetCode::SUCCESS,
+                      EX_ILLEGAL_ARGUMENT, "setTypeFailed");
+            return ndk::ScopedAStatus::ok();
+        }
+        default: {
+            LOG(ERROR) << __func__ << " unsupported tag: " << toString(tag);
+            return ndk::ScopedAStatus::fromExceptionCodeWithMessage(EX_ILLEGAL_ARGUMENT,
+                                                                    "DownmixTagNotSupported");
+        }
+    }
+}
+
+ndk::ScopedAStatus DownmixSw::getParameterSpecific(const Parameter::Id& id,
+                                                   Parameter::Specific* specific) {
+    auto tag = id.getTag();
+    RETURN_IF(Parameter::Id::downmixTag != tag, EX_ILLEGAL_ARGUMENT, "wrongIdTag");
+    auto dmId = id.get<Parameter::Id::downmixTag>();
+    auto dmIdTag = dmId.getTag();
+    switch (dmIdTag) {
+        case Downmix::Id::commonTag:
+            return getParameterDownmix(dmId.get<Downmix::Id::commonTag>(), specific);
+        default:
+            LOG(ERROR) << __func__ << " unsupported tag: " << toString(tag);
+            return ndk::ScopedAStatus::fromExceptionCodeWithMessage(EX_ILLEGAL_ARGUMENT,
+                                                                    "DownmixTagNotSupported");
+    }
+}
+
+ndk::ScopedAStatus DownmixSw::getParameterDownmix(const Downmix::Tag& tag,
+                                                  Parameter::Specific* specific) {
+    RETURN_IF(!mContext, EX_NULL_POINTER, "nullContext");
+    Downmix dmParam;
+    switch (tag) {
+        case Downmix::type: {
+            dmParam.set<Downmix::type>(mContext->getDmType());
+            break;
+        }
+        default: {
+            LOG(ERROR) << __func__ << " unsupported tag: " << toString(tag);
+            return ndk::ScopedAStatus::fromExceptionCodeWithMessage(EX_ILLEGAL_ARGUMENT,
+                                                                    "DownmixTagNotSupported");
+        }
+    }
+
+    specific->set<Parameter::Specific::downmix>(dmParam);
+    return ndk::ScopedAStatus::ok();
+}
+
+std::shared_ptr<EffectContext> DownmixSw::createContext(const Parameter::Common& common) {
+    if (mContext) {
+        LOG(DEBUG) << __func__ << " context already exist";
+    } else {
+        mContext = std::make_shared<DownmixSwContext>(1 /* statusFmqDepth */, common);
+    }
+
+    return mContext;
+}
+
+std::shared_ptr<EffectContext> DownmixSw::getContext() {
+    return mContext;
+}
+
+RetCode DownmixSw::releaseContext() {
+    if (mContext) {
+        mContext.reset();
+    }
+    return RetCode::SUCCESS;
+}
+
+// Processing method running in EffectWorker thread.
+IEffect::Status DownmixSw::effectProcessImpl(float* in, float* out, int samples) {
+    // TODO: get data buffer and process.
+    LOG(DEBUG) << __func__ << " in " << in << " out " << out << " samples " << samples;
+    for (int i = 0; i < samples; i++) {
+        *out++ = *in++;
+    }
+    return {STATUS_OK, samples, samples};
+}
+
+}  // namespace aidl::android::hardware::audio::effect
diff --git a/audio/aidl/default/downmix/DownmixSw.h b/audio/aidl/default/downmix/DownmixSw.h
new file mode 100644
index 0000000..51546c1
--- /dev/null
+++ b/audio/aidl/default/downmix/DownmixSw.h
@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#pragma once
+
+#include <aidl/android/hardware/audio/effect/BnEffect.h>
+#include <fmq/AidlMessageQueue.h>
+#include <cstdlib>
+#include <memory>
+
+#include "effect-impl/EffectImpl.h"
+#include "effect-impl/EffectUUID.h"
+
+namespace aidl::android::hardware::audio::effect {
+
+class DownmixSwContext final : public EffectContext {
+  public:
+    DownmixSwContext(int statusDepth, const Parameter::Common& common)
+        : EffectContext(statusDepth, common) {
+        LOG(DEBUG) << __func__;
+    }
+
+    RetCode setDmType(Downmix::Type type) {
+        // TODO : Add implementation to apply new type
+        mType = type;
+        return RetCode::SUCCESS;
+    }
+    Downmix::Type getDmType() const { return mType; }
+
+  private:
+    Downmix::Type mType = Downmix::Type::STRIP;
+};
+
+class DownmixSw final : public EffectImpl {
+  public:
+    static const std::string kEffectName;
+    static const Downmix::Capability kCapability;
+    static const Descriptor kDescriptor;
+    DownmixSw() { LOG(DEBUG) << __func__; }
+    ~DownmixSw() {
+        cleanUp();
+        LOG(DEBUG) << __func__;
+    }
+
+    ndk::ScopedAStatus getDescriptor(Descriptor* _aidl_return) override;
+    ndk::ScopedAStatus setParameterSpecific(const Parameter::Specific& specific) override;
+    ndk::ScopedAStatus getParameterSpecific(const Parameter::Id& id,
+                                            Parameter::Specific* specific) override;
+
+    std::shared_ptr<EffectContext> createContext(const Parameter::Common& common) override;
+    std::shared_ptr<EffectContext> getContext() override;
+    RetCode releaseContext() override;
+
+    std::string getEffectName() override { return kEffectName; };
+    IEffect::Status effectProcessImpl(float* in, float* out, int sample) override;
+
+  private:
+    std::shared_ptr<DownmixSwContext> mContext;
+
+    ndk::ScopedAStatus getParameterDownmix(const Downmix::Tag& tag, Parameter::Specific* specific);
+};
+}  // namespace aidl::android::hardware::audio::effect
diff --git a/audio/aidl/default/include/core-impl/Module.h b/audio/aidl/default/include/core-impl/Module.h
index 6baaa76..aa05d2a 100644
--- a/audio/aidl/default/include/core-impl/Module.h
+++ b/audio/aidl/default/include/core-impl/Module.h
@@ -92,6 +92,14 @@
                                            std::vector<VendorParameter>* _aidl_return) override;
     ndk::ScopedAStatus setVendorParameters(const std::vector<VendorParameter>& in_parameters,
                                            bool in_async) override;
+    ndk::ScopedAStatus addDeviceEffect(
+            int32_t in_portConfigId,
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect)
+            override;
+    ndk::ScopedAStatus removeDeviceEffect(
+            int32_t in_portConfigId,
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect)
+            override;
 
     void cleanUpPatch(int32_t patchId);
     ndk::ScopedAStatus createStreamContext(
diff --git a/audio/aidl/default/include/core-impl/Stream.h b/audio/aidl/default/include/core-impl/Stream.h
index e8b2c54..a5d240f 100644
--- a/audio/aidl/default/include/core-impl/Stream.h
+++ b/audio/aidl/default/include/core-impl/Stream.h
@@ -212,6 +212,12 @@
                                                    std::vector<VendorParameter>* _aidl_return) = 0;
     virtual ndk::ScopedAStatus setVendorParameters(
             const std::vector<VendorParameter>& in_parameters, bool in_async) = 0;
+    virtual ndk::ScopedAStatus addEffect(
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>&
+                    in_effect) = 0;
+    virtual ndk::ScopedAStatus removeEffect(
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>&
+                    in_effect) = 0;
 };
 
 class StreamCommon : public BnStreamCommon {
@@ -242,6 +248,20 @@
         return delegate != nullptr ? delegate->setVendorParameters(in_parameters, in_async)
                                    : ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
     }
+    ndk::ScopedAStatus addEffect(
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect)
+            override {
+        auto delegate = mDelegate.lock();
+        return delegate != nullptr ? delegate->addEffect(in_effect)
+                                   : ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
+    ndk::ScopedAStatus removeEffect(
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect)
+            override {
+        auto delegate = mDelegate.lock();
+        return delegate != nullptr ? delegate->removeEffect(in_effect)
+                                   : ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
+    }
     // It is possible that on the client side the proxy for IStreamCommon will outlive
     // the IStream* instance, and the server side IStream* instance will get destroyed
     // while this IStreamCommon instance is still alive.
@@ -257,6 +277,12 @@
                                            std::vector<VendorParameter>* _aidl_return) override;
     ndk::ScopedAStatus setVendorParameters(const std::vector<VendorParameter>& in_parameters,
                                            bool in_async) override;
+    ndk::ScopedAStatus addEffect(
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect)
+            override;
+    ndk::ScopedAStatus removeEffect(
+            const std::shared_ptr<::aidl::android::hardware::audio::effect::IEffect>& in_effect)
+            override;
 
     ndk::ScopedAStatus getStreamCommon(std::shared_ptr<IStreamCommon>* _aidl_return);
     ndk::ScopedAStatus init() {
diff --git a/audio/aidl/default/include/effect-impl/EffectUUID.h b/audio/aidl/default/include/effect-impl/EffectUUID.h
index 8c381c7..c9bb1f4 100644
--- a/audio/aidl/default/include/effect-impl/EffectUUID.h
+++ b/audio/aidl/default/include/effect-impl/EffectUUID.h
@@ -69,6 +69,12 @@
                                              0x11ed,
                                              0x9b6a,
                                              {0x02, 0x42, 0xac, 0x12, 0x00, 0x02}};
+// 93f04452-e4fe-41cc-91f9-e475b6d1d69f
+static const AudioUuid kDownmixImplUUID = {static_cast<int32_t>(0x93f04452),
+                                           0xe4fe,
+                                           0x41cc,
+                                           0x91f9,
+                                           {0xe4, 0x75, 0xb6, 0xd1, 0xd6, 0x9f}};
 // 0bed4300-ddd6-11db-8f34-0002a5d5c51b.
 static const AudioUuid kEqualizerTypeUUID = {static_cast<int32_t>(0x0bed4300),
                                              0xddd6,
diff --git a/audio/aidl/vts/Android.bp b/audio/aidl/vts/Android.bp
index 94de0d4..dcdecab 100644
--- a/audio/aidl/vts/Android.bp
+++ b/audio/aidl/vts/Android.bp
@@ -74,6 +74,12 @@
 }
 
 cc_test {
+    name: "VtsHalDownmixTargetTest",
+    defaults: ["VtsHalAudioTargetTestDefaults"],
+    srcs: ["VtsHalDownmixTargetTest.cpp"],
+}
+
+cc_test {
     name: "VtsHalEqualizerTargetTest",
     defaults: ["VtsHalAudioTargetTestDefaults"],
     srcs: ["VtsHalEqualizerTargetTest.cpp"],
diff --git a/audio/aidl/vts/VtsHalAudioCoreModuleTargetTest.cpp b/audio/aidl/vts/VtsHalAudioCoreModuleTargetTest.cpp
index 50fb981..2508afd 100644
--- a/audio/aidl/vts/VtsHalAudioCoreModuleTargetTest.cpp
+++ b/audio/aidl/vts/VtsHalAudioCoreModuleTargetTest.cpp
@@ -1746,6 +1746,33 @@
     }
 }
 
+// See b/262930731. In the absence of offloaded effect implementations,
+// currently we can only pass a nullptr, and the HAL module must either reject
+// it as an invalid argument, or say that offloaded effects are not supported.
+TEST_P(AudioCoreModule, AddRemoveEffectInvalidArguments) {
+    ndk::ScopedAStatus addEffectStatus = module->addDeviceEffect(-1, nullptr);
+    ndk::ScopedAStatus removeEffectStatus = module->removeDeviceEffect(-1, nullptr);
+    const bool isSupported = addEffectStatus.getExceptionCode() != EX_UNSUPPORTED_OPERATION;
+    if (isSupported) {
+        EXPECT_EQ(EX_ILLEGAL_ARGUMENT, addEffectStatus.getExceptionCode());
+        EXPECT_EQ(EX_ILLEGAL_ARGUMENT, removeEffectStatus.getExceptionCode());
+    } else if (EX_UNSUPPORTED_OPERATION != removeEffectStatus.getExceptionCode()) {
+        GTEST_FAIL() << "addEffect and removeEffect must be either supported or not supported "
+                     << "together";
+    } else {
+        GTEST_SKIP() << "Offloaded effects not supported";
+    }
+    // Test rejection of a nullptr effect with a valid device port Id.
+    ASSERT_NO_FATAL_FAILURE(SetUpModuleConfig());
+    const auto configs = moduleConfig->getPortConfigsForAttachedDevicePorts();
+    for (const auto& config : configs) {
+        WithAudioPortConfig portConfig(config);
+        ASSERT_NO_FATAL_FAILURE(portConfig.SetUp(module.get()));
+        EXPECT_STATUS(EX_ILLEGAL_ARGUMENT, module->addDeviceEffect(portConfig.getId(), nullptr));
+        EXPECT_STATUS(EX_ILLEGAL_ARGUMENT, module->removeDeviceEffect(portConfig.getId(), nullptr));
+    }
+}
+
 class AudioCoreTelephony : public AudioCoreModuleBase, public testing::TestWithParam<std::string> {
   public:
     void SetUp() override {
@@ -1899,9 +1926,7 @@
         }
         WithStream<Stream> stream(portConfig.value());
         ASSERT_NO_FATAL_FAILURE(stream.SetUpPortConfig(module.get()));
-        // The buffer size of 1 frame should be impractically small, and thus
-        // less than any minimum buffer size suggested by any HAL.
-        for (long bufferSize : std::array<long, 4>{-1, 0, 1, std::numeric_limits<long>::max()}) {
+        for (long bufferSize : std::array<long, 3>{-1, 0, std::numeric_limits<long>::max()}) {
             EXPECT_STATUS(EX_ILLEGAL_ARGUMENT, stream.SetUpNoChecks(module.get(), bufferSize))
                     << "for the buffer size " << bufferSize;
             EXPECT_EQ(nullptr, stream.get());
@@ -2080,6 +2105,43 @@
         }
     }
 
+    // See b/262930731. In the absence of offloaded effect implementations,
+    // currently we can only pass a nullptr, and the HAL module must either reject
+    // it as an invalid argument, or say that offloaded effects are not supported.
+    void AddRemoveEffectInvalidArguments() {
+        const auto ports =
+                moduleConfig->getMixPorts(IOTraits<Stream>::is_input, false /*attachedOnly*/);
+        if (ports.empty()) {
+            GTEST_SKIP() << "No mix ports";
+        }
+        bool atLeastOneSupports = false;
+        for (const auto& port : ports) {
+            const auto portConfig = moduleConfig->getSingleConfigForMixPort(true, port);
+            if (!portConfig.has_value()) continue;
+            WithStream<Stream> stream(portConfig.value());
+            ASSERT_NO_FATAL_FAILURE(stream.SetUp(module.get(), kDefaultBufferSizeFrames));
+            std::shared_ptr<IStreamCommon> streamCommon;
+            ASSERT_IS_OK(stream.get()->getStreamCommon(&streamCommon));
+            ASSERT_NE(nullptr, streamCommon);
+            ndk::ScopedAStatus addEffectStatus = streamCommon->addEffect(nullptr);
+            ndk::ScopedAStatus removeEffectStatus = streamCommon->removeEffect(nullptr);
+            const bool isSupported = addEffectStatus.getExceptionCode() != EX_UNSUPPORTED_OPERATION;
+            if (isSupported) {
+                EXPECT_EQ(EX_ILLEGAL_ARGUMENT, addEffectStatus.getExceptionCode());
+                EXPECT_EQ(EX_ILLEGAL_ARGUMENT, removeEffectStatus.getExceptionCode());
+                atLeastOneSupports = true;
+            } else if (EX_UNSUPPORTED_OPERATION != removeEffectStatus.getExceptionCode()) {
+                ADD_FAILURE()
+                        << "addEffect and removeEffect must be either supported or not supported "
+                        << "together";
+                atLeastOneSupports = true;
+            }
+        }
+        if (!atLeastOneSupports) {
+            GTEST_SKIP() << "Offloaded effects not supported";
+        }
+    }
+
     void OpenTwiceSamePortConfigImpl(const AudioPortConfig& portConfig) {
         WithStream<Stream> stream1(portConfig);
         ASSERT_NO_FATAL_FAILURE(stream1.SetUp(module.get(), kDefaultBufferSizeFrames));
@@ -2157,6 +2219,7 @@
 TEST_IN_AND_OUT_STREAM(GetVendorParameters);
 TEST_IN_AND_OUT_STREAM(SetVendorParameters);
 TEST_IN_AND_OUT_STREAM(HwGainHwVolume);
+TEST_IN_AND_OUT_STREAM(AddRemoveEffectInvalidArguments);
 
 namespace aidl::android::hardware::audio::core {
 std::ostream& operator<<(std::ostream& os, const IStreamIn::MicrophoneDirection& md) {
diff --git a/audio/aidl/vts/VtsHalDownmixTargetTest.cpp b/audio/aidl/vts/VtsHalDownmixTargetTest.cpp
new file mode 100644
index 0000000..8612660
--- /dev/null
+++ b/audio/aidl/vts/VtsHalDownmixTargetTest.cpp
@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#define LOG_TAG "VtsHalDownmixTargetTest"
+
+#include <Utils.h>
+#include <aidl/Vintf.h>
+#include "EffectHelper.h"
+
+using namespace android;
+
+using aidl::android::hardware::audio::effect::Capability;
+using aidl::android::hardware::audio::effect::Descriptor;
+using aidl::android::hardware::audio::effect::Downmix;
+using aidl::android::hardware::audio::effect::IEffect;
+using aidl::android::hardware::audio::effect::IFactory;
+using aidl::android::hardware::audio::effect::kDownmixTypeUUID;
+using aidl::android::hardware::audio::effect::kEffectNullUuid;
+using aidl::android::hardware::audio::effect::Parameter;
+
+/**
+ * Here we focus on specific parameter checking, general IEffect interfaces testing performed in
+ * VtsAudioEffectTargetTest.
+ */
+enum ParamName { PARAM_INSTANCE_NAME, PARAM_TYPE };
+using DownmixParamTestParam =
+        std::tuple<std::pair<std::shared_ptr<IFactory>, Descriptor>, Downmix::Type>;
+
+// Testing for enum values
+const std::vector<Downmix::Type> kTypeValues = {Downmix::Type::STRIP, Downmix::Type::FOLD};
+
+class DownmixParamTest : public ::testing::TestWithParam<DownmixParamTestParam>,
+                         public EffectHelper {
+  public:
+    DownmixParamTest() : mParamType(std::get<PARAM_TYPE>(GetParam())) {
+        std::tie(mFactory, mDescriptor) = std::get<PARAM_INSTANCE_NAME>(GetParam());
+    }
+
+    void SetUp() override {
+        ASSERT_NE(nullptr, mFactory);
+        ASSERT_NO_FATAL_FAILURE(create(mFactory, mEffect, mDescriptor));
+
+        Parameter::Specific specific = getDefaultParamSpecific();
+        Parameter::Common common = EffectHelper::createParamCommon(
+                0 /* session */, 1 /* ioHandle */, 44100 /* iSampleRate */, 44100 /* oSampleRate */,
+                kInputFrameCount /* iFrameCount */, kOutputFrameCount /* oFrameCount */);
+        IEffect::OpenEffectReturn ret;
+        ASSERT_NO_FATAL_FAILURE(open(mEffect, common, specific, &ret, EX_NONE));
+        ASSERT_NE(nullptr, mEffect);
+    }
+
+    void TearDown() override {
+        ASSERT_NO_FATAL_FAILURE(close(mEffect));
+        ASSERT_NO_FATAL_FAILURE(destroy(mFactory, mEffect));
+    }
+
+    static const long kInputFrameCount = 0x100, kOutputFrameCount = 0x100;
+    std::shared_ptr<IFactory> mFactory;
+    std::shared_ptr<IEffect> mEffect;
+    Descriptor mDescriptor;
+    Downmix::Type mParamType = Downmix::Type::STRIP;
+
+    void SetAndGetDownmixParameters() {
+        for (auto& it : mTags) {
+            auto& tag = it.first;
+            auto& dm = it.second;
+
+            // set parameter
+            Parameter expectParam;
+            Parameter::Specific specific;
+            specific.set<Parameter::Specific::downmix>(dm);
+            expectParam.set<Parameter::specific>(specific);
+            // All values are valid, set parameter should succeed
+            EXPECT_STATUS(EX_NONE, mEffect->setParameter(expectParam)) << expectParam.toString();
+
+            // get parameter
+            Parameter getParam;
+            Parameter::Id id;
+            Downmix::Id dmId;
+            dmId.set<Downmix::Id::commonTag>(tag);
+            id.set<Parameter::Id::downmixTag>(dmId);
+            EXPECT_STATUS(EX_NONE, mEffect->getParameter(id, &getParam));
+
+            EXPECT_EQ(expectParam, getParam);
+        }
+    }
+
+    void addTypeParam(Downmix::Type type) {
+        Downmix dm;
+        dm.set<Downmix::type>(type);
+        mTags.push_back({Downmix::type, dm});
+    }
+
+    Parameter::Specific getDefaultParamSpecific() {
+        Downmix dm = Downmix::make<Downmix::type>(Downmix::Type::STRIP);
+        Parameter::Specific specific = Parameter::Specific::make<Parameter::Specific::downmix>(dm);
+        return specific;
+    }
+
+  private:
+    std::vector<std::pair<Downmix::Tag, Downmix>> mTags;
+    void CleanUp() { mTags.clear(); }
+};
+
+TEST_P(DownmixParamTest, SetAndGetType) {
+    EXPECT_NO_FATAL_FAILURE(addTypeParam(mParamType));
+    SetAndGetDownmixParameters();
+}
+
+INSTANTIATE_TEST_SUITE_P(
+        DownmixTest, DownmixParamTest,
+        ::testing::Combine(testing::ValuesIn(EffectFactoryHelper::getAllEffectDescriptors(
+                                   IFactory::descriptor, kDownmixTypeUUID)),
+                           testing::ValuesIn(kTypeValues)),
+        [](const testing::TestParamInfo<DownmixParamTest::ParamType>& info) {
+            auto descriptor = std::get<PARAM_INSTANCE_NAME>(info.param).second;
+            std::string type = std::to_string(static_cast<int>(std::get<PARAM_TYPE>(info.param)));
+            std::string name = "Implementor_" + descriptor.common.implementor + "_name_" +
+                               descriptor.common.name + "_UUID_" +
+                               descriptor.common.id.uuid.toString() + "_type" + type;
+            std::replace_if(
+                    name.begin(), name.end(), [](const char c) { return !std::isalnum(c); }, '_');
+            return name;
+        });
+
+GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(DownmixParamTest);
+
+int main(int argc, char** argv) {
+    ::testing::InitGoogleTest(&argc, argv);
+    ABinderProcess_setThreadPoolMaxThreadCount(1);
+    ABinderProcess_startThreadPool();
+    return RUN_ALL_TESTS();
+}
diff --git a/automotive/vehicle/aidl/Android.bp b/automotive/vehicle/aidl/Android.bp
index 9aeb4d2..88d1c74 100644
--- a/automotive/vehicle/aidl/Android.bp
+++ b/automotive/vehicle/aidl/Android.bp
@@ -27,6 +27,7 @@
     srcs: [
         "android/hardware/automotive/vehicle/**/*.aidl",
     ],
+    frozen: true,
     stability: "vintf",
     backend: {
         cpp: {
diff --git a/biometrics/common/aidl/Android.bp b/biometrics/common/aidl/Android.bp
index 167e0c7..0f795f8 100644
--- a/biometrics/common/aidl/Android.bp
+++ b/biometrics/common/aidl/Android.bp
@@ -13,6 +13,7 @@
     srcs: [
         "android/hardware/biometrics/common/*.aidl",
     ],
+    frozen: true,
     stability: "vintf",
     backend: {
         java: {
diff --git a/input/common/aidl/Android.bp b/input/common/aidl/Android.bp
index 95a14b2..5aa820c 100644
--- a/input/common/aidl/Android.bp
+++ b/input/common/aidl/Android.bp
@@ -12,6 +12,7 @@
     host_supported: true,
     vendor_available: true,
     srcs: ["android/hardware/input/common/*.aidl"],
+    frozen: true,
     stability: "vintf",
     backend: {
         cpp: {
diff --git a/radio/aidl/Android.bp b/radio/aidl/Android.bp
index 98eafc1..0088264 100644
--- a/radio/aidl/Android.bp
+++ b/radio/aidl/Android.bp
@@ -12,6 +12,7 @@
     vendor_available: true,
     host_supported: true,
     srcs: ["android/hardware/radio/*.aidl"],
+    frozen: true,
     stability: "vintf",
     backend: {
         cpp: {
@@ -35,6 +36,7 @@
     vendor_available: true,
     host_supported: true,
     srcs: ["android/hardware/radio/config/*.aidl"],
+    frozen: true,
     stability: "vintf",
     imports: ["android.hardware.radio"],
     backend: {