diff --git a/audio/aidl/default/Android.bp b/audio/aidl/default/Android.bp
index b9b8cd8..803880f 100644
--- a/audio/aidl/default/Android.bp
+++ b/audio/aidl/default/Android.bp
@@ -128,6 +128,7 @@
     shared_libs: [
         "libbassboostsw",
         "libbundleaidl",
+        "libdownmixsw",
         "libdynamicsprocessingsw",
         "libenvreverbsw",
         "libequalizersw",
diff --git a/audio/aidl/default/audio_effects_config.xml b/audio/aidl/default/audio_effects_config.xml
index d22c349..c08f913 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="downmixsw" path="libdownmixsw.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="downmixsw" uuid="fa8187ba-588b-11ed-9b6a-0242ac120002"/>
         <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_enhancersw" uuid="fa819610-588b-11ed-9b6a-0242ac120002"/>
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