Add haptic-generating effect.

Haptic generator is an audio effect that will generate haptic data from
audio data.

Test: manually
Bug: 136490803
Change-Id: I0621371801fdddf2ac2c3f8a5503c3a076cc4980
diff --git a/media/libeffects/data/audio_effects.xml b/media/libeffects/data/audio_effects.xml
index 2e5f529..93a2181 100644
--- a/media/libeffects/data/audio_effects.xml
+++ b/media/libeffects/data/audio_effects.xml
@@ -21,6 +21,7 @@
         <library name="downmix" path="libdownmix.so"/>
         <library name="loudness_enhancer" path="libldnhncr.so"/>
         <library name="dynamics_processing" path="libdynproc.so"/>
+        <library name="haptic_generator" path="libhapticgenerator.so"/>
     </libraries>
 
     <!-- list of effects to load.
@@ -58,6 +59,7 @@
         <effect name="downmix" library="downmix" uuid="93f04452-e4fe-41cc-91f9-e475b6d1d69f"/>
         <effect name="loudness_enhancer" library="loudness_enhancer" uuid="fa415329-2034-4bea-b5dc-5b381c8d1e2c"/>
         <effect name="dynamics_processing" library="dynamics_processing" uuid="e0e6539b-1781-7261-676f-6d7573696340"/>
+        <effect name="haptic_generator" library="haptic_generator" uuid="97c4acd1-8b82-4f2f-832e-c2fe5d7a9931"/>
     </effects>
 
     <!-- Audio pre processor configurations.
diff --git a/media/libeffects/hapticgenerator/Android.bp b/media/libeffects/hapticgenerator/Android.bp
new file mode 100644
index 0000000..ac40e33
--- /dev/null
+++ b/media/libeffects/hapticgenerator/Android.bp
@@ -0,0 +1,49 @@
+// Copyright (C) 2020 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.
+
+// HapticGenerator library
+cc_library_shared {
+    name: "libhapticgenerator",
+
+    vendor: true,
+
+    srcs: [
+        "EffectHapticGenerator.cpp",
+        "Processors.cpp",
+    ],
+
+    cflags: [
+        "-O2", // Turning on the optimization in order to reduce effect processing time.
+               // The latency is around 1/5 less than without the optimization.
+        "-Wall",
+        "-Werror",
+        "-ffast-math", // This is needed for the non-zero coefficients optimization for
+                       // BiquadFilter. Try the biquad_filter_benchmark test in audio_utils
+                       // with/without `-ffast-math` for more context.
+        "-fvisibility=hidden",
+    ],
+
+    shared_libs: [
+        "libaudioutils",
+        "liblog",
+        "libutils",
+    ],
+
+    relative_install_path: "soundfx",
+
+    header_libs: [
+        "libaudioeffects",
+    ],
+}
+
diff --git a/media/libeffects/hapticgenerator/EffectHapticGenerator.cpp b/media/libeffects/hapticgenerator/EffectHapticGenerator.cpp
new file mode 100644
index 0000000..3d3fce8
--- /dev/null
+++ b/media/libeffects/hapticgenerator/EffectHapticGenerator.cpp
@@ -0,0 +1,485 @@
+/*
+ * Copyright (C) 2020 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 "EffectHG"
+//#define LOG_NDEBUG 0
+#include <utils/Log.h>
+
+#include "EffectHapticGenerator.h"
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+
+#include <errno.h>
+#include <inttypes.h>
+
+#include <audio_effects/effect_hapticgenerator.h>
+#include <audio_utils/format.h>
+#include <system/audio.h>
+
+// This is the only symbol that needs to be exported
+__attribute__ ((visibility ("default")))
+audio_effect_library_t AUDIO_EFFECT_LIBRARY_INFO_SYM = {
+        .tag = AUDIO_EFFECT_LIBRARY_TAG,
+        .version = EFFECT_LIBRARY_API_VERSION,
+        .name = "HapticGenerator Library",
+        .implementor = "The Android Open Source Project",
+        .create_effect = android::audio_effect::haptic_generator::HapticGeneratorLib_Create,
+        .release_effect = android::audio_effect::haptic_generator::HapticGeneratorLib_Release,
+        .get_descriptor = android::audio_effect::haptic_generator::HapticGeneratorLib_GetDescriptor,
+};
+
+namespace android::audio_effect::haptic_generator {
+
+// effect_handle_t interface implementation for haptic generator effect
+const struct effect_interface_s gHapticGeneratorInterface = {
+        HapticGenerator_Process,
+        HapticGenerator_Command,
+        HapticGenerator_GetDescriptor,
+        nullptr /* no process_reverse function, no reference stream needed */
+};
+
+//-----------------------------------------------------------------------------
+// Effect Descriptor
+//-----------------------------------------------------------------------------
+
+// UUIDs for effect types have been generated from http://www.itu.int/ITU-T/asn1/uuid.html
+// Haptic Generator
+static const effect_descriptor_t gHgDescriptor = {
+        FX_IID_HAPTICGENERATOR_, // type
+        {0x97c4acd1, 0x8b82, 0x4f2f, 0x832e, {0xc2, 0xfe, 0x5d, 0x7a, 0x99, 0x31}}, // uuid
+        EFFECT_CONTROL_API_VERSION,
+        EFFECT_FLAG_TYPE_INSERT | EFFECT_FLAG_INSERT_FIRST,
+        0, // FIXME what value should be reported? // cpu load
+        0, // FIXME what value should be reported? // memory usage
+        "Haptic Generator",
+        "The Android Open Source Project"
+};
+
+//-----------------------------------------------------------------------------
+// Internal functions
+//-----------------------------------------------------------------------------
+
+namespace {
+
+int HapticGenerator_Init(struct HapticGeneratorContext *context) {
+    context->itfe = &gHapticGeneratorInterface;
+
+    context->config.inputCfg.accessMode = EFFECT_BUFFER_ACCESS_READ;
+    context->config.inputCfg.channels = AUDIO_CHANNEL_OUT_STEREO;
+    context->config.inputCfg.format = AUDIO_FORMAT_PCM_FLOAT;
+    context->config.inputCfg.samplingRate = 0;
+    context->config.inputCfg.bufferProvider.getBuffer = nullptr;
+    context->config.inputCfg.bufferProvider.releaseBuffer = nullptr;
+    context->config.inputCfg.bufferProvider.cookie = nullptr;
+    context->config.inputCfg.mask = EFFECT_CONFIG_ALL;
+    context->config.outputCfg.accessMode = EFFECT_BUFFER_ACCESS_ACCUMULATE;
+    context->config.outputCfg.channels = AUDIO_CHANNEL_OUT_STEREO;
+    context->config.outputCfg.format = AUDIO_FORMAT_PCM_FLOAT;
+    context->config.outputCfg.samplingRate = 0;
+    context->config.outputCfg.bufferProvider.getBuffer = nullptr;
+    context->config.outputCfg.bufferProvider.releaseBuffer = nullptr;
+    context->config.outputCfg.bufferProvider.cookie = nullptr;
+    context->config.outputCfg.mask = EFFECT_CONFIG_ALL;
+
+    memset(&context->param, 0, sizeof(struct HapticGeneratorParam));
+
+    context->state = HAPTICGENERATOR_STATE_INITIALIZED;
+    return 0;
+}
+
+void addBiquadFilter(
+        std::vector<std::function<void(float *, const float *, size_t)>> &processingChain,
+        struct HapticGeneratorProcessorsRecord &processorsRecord,
+        std::shared_ptr<BiquadFilter> filter) {
+    // The process chain captures the shared pointer of the filter in lambda.
+    // The process record will keep a shared pointer to the filter so that it is possible to access
+    // the filter outside of the process chain.
+    processorsRecord.filters.push_back(filter);
+    processingChain.push_back([filter](float *out, const float *in, size_t frameCount) {
+            filter->process(out, in, frameCount);
+    });
+}
+
+/**
+ * \brief build haptic generator processing chain.
+ *
+ * \param processingChain
+ * \param processorsRecord a structure to cache all the shared pointers for processors
+ * \param sampleRate the audio sampling rate. Use a float here as it may be used to create filters
+ * \param channelCount haptic channel count
+ */
+void HapticGenerator_buildProcessingChain(
+        std::vector<std::function<void(float*, const float*, size_t)>>& processingChain,
+        struct HapticGeneratorProcessorsRecord& processorsRecord,
+        float sampleRate, size_t channelCount) {
+    float highPassCornerFrequency = 100.0f;
+    auto hpf = createHPF2(highPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, hpf);
+    float lowPassCornerFrequency = 3000.0f;
+    auto lpf = createLPF2(lowPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, lpf);
+
+    auto ramp = std::make_shared<Ramp>(channelCount);
+    // The process chain captures the shared pointer of the ramp in lambda. It will be the only
+    // reference to the ramp.
+    // The process record will keep a weak pointer to the ramp so that it is possible to access
+    // the ramp outside of the process chain.
+    processorsRecord.ramps.push_back(ramp);
+    processingChain.push_back([ramp](float *out, const float *in, size_t frameCount) {
+            ramp->process(out, in, frameCount);
+    });
+
+    highPassCornerFrequency = 60.0f;
+    hpf = createHPF2(highPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, hpf);
+    lowPassCornerFrequency = 700.0f;
+    lpf = createLPF2(lowPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, lpf);
+
+    lowPassCornerFrequency = 5.0f;
+    float normalizationPower = -0.3f;
+    // The process chain captures the shared pointer of the slow envelope in lambda. It will
+    // be the only reference to the slow envelope.
+    // The process record will keep a weak pointer to the slow envelope so that it is possible
+    // to access the slow envelope outside of the process chain.
+    auto slowEnv = std::make_shared<SlowEnvelope>(
+            lowPassCornerFrequency, sampleRate, normalizationPower, channelCount);
+    processorsRecord.slowEnvs.push_back(slowEnv);
+    processingChain.push_back([slowEnv](float *out, const float *in, size_t frameCount) {
+            slowEnv->process(out, in, frameCount);
+    });
+
+    lowPassCornerFrequency = 400.0f;
+    lpf = createLPF2(lowPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, lpf);
+    lowPassCornerFrequency = 500.0f;
+    lpf = createLPF2(lowPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, lpf);
+
+    auto apf = createAPF2(400.0f, 200.0f, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, apf);
+    apf = createAPF2(100.0f, 50.0f, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, apf);
+    float allPassCornerFrequency = 25.0f;
+    apf = createAPF(allPassCornerFrequency, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, apf);
+
+    float resonantFrequency = 150.0f;
+    float bandpassQ = 1.0f;
+    auto bpf = createBPF(resonantFrequency, bandpassQ, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, bpf);
+
+    float zeroQ = 8.0f;
+    float poleQ = 4.0f;
+    auto bsf = createBSF(resonantFrequency, zeroQ, poleQ, sampleRate, channelCount);
+    addBiquadFilter(processingChain, processorsRecord, bsf);
+}
+
+int HapticGenerator_Configure(struct HapticGeneratorContext *context, effect_config_t *config) {
+    if (config->inputCfg.samplingRate != config->outputCfg.samplingRate ||
+        config->inputCfg.format != config->outputCfg.format ||
+        config->inputCfg.format != AUDIO_FORMAT_PCM_FLOAT ||
+        config->inputCfg.channels != config->outputCfg.channels ||
+        config->inputCfg.buffer.frameCount != config->outputCfg.buffer.frameCount) {
+        return -EINVAL;
+    }
+    if (&context->config != config) {
+        context->processingChain.clear();
+        context->processorsRecord.filters.clear();
+        context->processorsRecord.ramps.clear();
+        context->processorsRecord.slowEnvs.clear();
+        memcpy(&context->config, config, sizeof(effect_config_t));
+        context->param.audioChannelCount = audio_channel_count_from_out_mask(
+                ((audio_channel_mask_t) config->inputCfg.channels) & ~AUDIO_CHANNEL_HAPTIC_ALL);
+        context->param.hapticChannelCount = audio_channel_count_from_out_mask(
+                ((audio_channel_mask_t) config->outputCfg.channels) & AUDIO_CHANNEL_HAPTIC_ALL);
+        ALOG_ASSERT(context->param.hapticChannelCount <= 2,
+                    "haptic channel count(%zu) is too large",
+                    context->param.hapticChannelCount);
+        context->audioDataBytesPerFrame = audio_bytes_per_frame(
+                context->param.audioChannelCount, (audio_format_t) config->inputCfg.format);
+        for (size_t i = 0; i < context->param.hapticChannelCount; ++i) {
+            // By default, use the first audio channel to generate haptic channels.
+            context->param.hapticChannelSource[i] = 0;
+        }
+
+        HapticGenerator_buildProcessingChain(context->processingChain,
+                                             context->processorsRecord,
+                                             config->inputCfg.samplingRate,
+                                             context->param.hapticChannelCount);
+    }
+    return 0;
+}
+
+int HapticGenerator_Reset(struct HapticGeneratorContext *context) {
+    for (auto& filter : context->processorsRecord.filters) {
+        filter->clear();
+    }
+    for (auto& slowEnv : context->processorsRecord.slowEnvs) {
+        slowEnv->clear();
+    }
+    return 0;
+}
+
+int HapticGenerator_SetParameter(struct HapticGeneratorContext *context __unused,
+                                 int32_t param __unused,
+                                 uint32_t size __unused,
+                                 void *value __unused) {
+    ALOGW("Setparameter is not implemented in HapticGenerator");
+    return -ENOSYS;
+}
+
+/**
+ * \brief run the processing chain to generate haptic data from audio data
+ *
+ * \param processingChain the processing chain for generating haptic data
+ * \param buf1 a buffer contains raw audio data
+ * \param buf2 a buffer that is large enough to keep all the data
+ * \param frameCount frame count of the data
+ * \return a pointer to the output buffer
+ */
+float* HapticGenerator_runProcessingChain(
+        const std::vector<std::function<void(float*, const float*, size_t)>>& processingChain,
+        float* buf1, float* buf2, size_t frameCount) {
+    float *in = buf1;
+    float *out = buf2;
+    for (const auto processingFunc : processingChain) {
+        processingFunc(out, in, frameCount);
+        std::swap(in, out);
+    }
+    return in;
+}
+
+} // namespace (anonymous)
+
+//-----------------------------------------------------------------------------
+// Effect API Implementation
+//-----------------------------------------------------------------------------
+
+/*--- Effect Library Interface Implementation ---*/
+
+int32_t HapticGeneratorLib_Create(const effect_uuid_t *uuid,
+                                  int32_t sessionId __unused,
+                                  int32_t ioId __unused,
+                                  effect_handle_t *handle) {
+    if (handle == nullptr || uuid == nullptr) {
+        return -EINVAL;
+    }
+
+    if (memcmp(uuid, &gHgDescriptor.uuid, sizeof(*uuid)) != 0) {
+        return -EINVAL;
+    }
+
+    HapticGeneratorContext *context = new HapticGeneratorContext;
+    HapticGenerator_Init(context);
+
+    *handle = (effect_handle_t) context;
+    ALOGV("%s context is %p", __func__, context);
+    return 0;
+}
+
+int32_t HapticGeneratorLib_Release(effect_handle_t handle) {
+    HapticGeneratorContext *context = (HapticGeneratorContext *) handle;
+    delete context;
+    return 0;
+}
+
+int32_t HapticGeneratorLib_GetDescriptor(const effect_uuid_t *uuid,
+                                         effect_descriptor_t *descriptor) {
+
+    if (descriptor == nullptr || uuid == nullptr) {
+        ALOGE("%s() called with NULL pointer", __func__);
+        return -EINVAL;
+    }
+
+    if (memcmp(uuid, &gHgDescriptor.uuid, sizeof(*uuid)) == 0) {
+        *descriptor = gHgDescriptor;
+        return 0;
+    }
+
+    return -EINVAL;
+}
+
+/*--- Effect Control Interface Implementation ---*/
+
+int32_t HapticGenerator_Process(effect_handle_t self,
+                                audio_buffer_t *inBuffer, audio_buffer_t *outBuffer) {
+    HapticGeneratorContext *context = (HapticGeneratorContext *) self;
+
+    if (inBuffer == nullptr || inBuffer->raw == nullptr
+            || outBuffer == nullptr || outBuffer->raw == nullptr) {
+        return 0;
+    }
+
+    // The audio data must not be modified but just written to
+    // output buffer according the access mode.
+    size_t audioBytes = context->audioDataBytesPerFrame * inBuffer->frameCount;
+    size_t audioSampleCount = inBuffer->frameCount * context->param.audioChannelCount;
+    if (inBuffer->raw != outBuffer->raw) {
+        if (context->config.outputCfg.accessMode == EFFECT_BUFFER_ACCESS_ACCUMULATE) {
+            for (size_t i = 0; i < audioSampleCount; ++i) {
+                outBuffer->f32[i] += inBuffer->f32[i];
+            }
+        } else {
+            memcpy(outBuffer->raw, inBuffer->raw, audioBytes);
+        }
+    }
+
+    if (context->state != HAPTICGENERATOR_STATE_ACTIVE) {
+        ALOGE("State(%d) is not HAPTICGENERATOR_STATE_ACTIVE when calling %s",
+                context->state, __func__);
+        return -ENODATA;
+    }
+
+    // Resize buffer if the haptic sample count is greater than buffer size.
+    size_t hapticSampleCount = inBuffer->frameCount * context->param.hapticChannelCount;
+    if (hapticSampleCount > context->inputBuffer.size()) {
+        // The context->inputBuffer and context->outputBuffer must have the same size,
+        // which must be at least the haptic sample count.
+        context->inputBuffer.resize(hapticSampleCount);
+        context->outputBuffer.resize(hapticSampleCount);
+    }
+
+    // Construct input buffer according to haptic channel source
+    for (size_t i = 0; i < inBuffer->frameCount; ++i) {
+        for (size_t j = 0; j < context->param.hapticChannelCount; ++j) {
+            context->inputBuffer[i * context->param.hapticChannelCount + j] =
+                    inBuffer->f32[i * context->param.audioChannelCount
+                            + context->param.hapticChannelSource[j]];
+        }
+    }
+
+    float* hapticOutBuffer = HapticGenerator_runProcessingChain(
+            context->processingChain, context->inputBuffer.data(),
+            context->outputBuffer.data(), inBuffer->frameCount);
+
+    // For haptic data, the haptic playback thread will copy the data from effect input buffer,
+    // which contains haptic data at the end of the buffer, directly to sink buffer.
+    // In that case, copy haptic data to input buffer instead of output buffer.
+    // Note: this may not work with rpc/binder calls
+    memcpy_by_audio_format(static_cast<char*>(inBuffer->raw) + audioBytes,
+                           static_cast<audio_format_t>(context->config.outputCfg.format),
+                           hapticOutBuffer,
+                           AUDIO_FORMAT_PCM_FLOAT,
+                           hapticSampleCount);
+
+    return 0;
+}
+
+int32_t HapticGenerator_Command(effect_handle_t self, uint32_t cmdCode, uint32_t cmdSize,
+                                void *cmdData, uint32_t *replySize, void *replyData) {
+    HapticGeneratorContext *context = (HapticGeneratorContext *) self;
+
+    if (context == nullptr || context->state == HAPTICGENERATOR_STATE_UNINITIALIZED) {
+        return -EINVAL;
+    }
+
+    ALOGV("HapticGenerator_Command command %u cmdSize %u", cmdCode, cmdSize);
+
+    switch (cmdCode) {
+        case EFFECT_CMD_INIT:
+            if (replyData == nullptr || replySize == nullptr || *replySize != sizeof(int)) {
+                return -EINVAL;
+            }
+            *(int *) replyData = HapticGenerator_Init(context);
+            break;
+
+        case EFFECT_CMD_SET_CONFIG:
+            if (cmdData == nullptr || cmdSize != sizeof(effect_config_t)
+                || replyData == nullptr || replySize == nullptr || *replySize != sizeof(int)) {
+                return -EINVAL;
+            }
+            *(int *) replyData = HapticGenerator_Configure(
+                    context, (effect_config_t *) cmdData);
+            break;
+
+        case EFFECT_CMD_RESET:
+            HapticGenerator_Reset(context);
+            break;
+
+        case EFFECT_CMD_GET_PARAM:
+            ALOGV("HapticGenerator_Command EFFECT_CMD_GET_PARAM cmdData %p,"
+                  "*replySize %u, replyData: %p",
+                  cmdData, *replySize, replyData);
+            break;
+
+        case EFFECT_CMD_SET_PARAM: {
+            ALOGV("HapticGenerator_Command EFFECT_CMD_SET_PARAM cmdSize %d cmdData %p, "
+                  "*replySize %u, replyData %p", cmdSize, cmdData, *replySize, replyData);
+            if (cmdData == nullptr || (cmdSize < (int) (sizeof(effect_param_t) + sizeof(int32_t)))
+                || replyData == nullptr || replySize == nullptr ||
+                *replySize != (int) sizeof(int32_t)) {
+                return -EINVAL;
+            }
+            effect_param_t *cmd = (effect_param_t *) cmdData;
+            *(int *) replyData = HapticGenerator_SetParameter(
+                    context, *(int32_t *) cmd->data, cmd->vsize, cmd->data + sizeof(int32_t));
+        }
+            break;
+
+        case EFFECT_CMD_ENABLE:
+            if (replyData == nullptr || replySize == nullptr || *replySize != sizeof(int)) {
+                return -EINVAL;
+            }
+            if (context->state != HAPTICGENERATOR_STATE_INITIALIZED) {
+                return -ENOSYS;
+            }
+            context->state = HAPTICGENERATOR_STATE_ACTIVE;
+            ALOGV("EFFECT_CMD_ENABLE() OK");
+            *(int *) replyData = 0;
+            break;
+
+        case EFFECT_CMD_DISABLE:
+            if (replyData == nullptr || replySize == nullptr || *replySize != sizeof(int)) {
+                return -EINVAL;
+            }
+            if (context->state != HAPTICGENERATOR_STATE_ACTIVE) {
+                return -ENOSYS;
+            }
+            context->state = HAPTICGENERATOR_STATE_INITIALIZED;
+            ALOGV("EFFECT_CMD_DISABLE() OK");
+            *(int *) replyData = 0;
+            break;
+
+        case EFFECT_CMD_SET_VOLUME:
+        case EFFECT_CMD_SET_DEVICE:
+        case EFFECT_CMD_SET_AUDIO_MODE:
+            break;
+
+        default:
+            ALOGW("HapticGenerator_Command invalid command %u", cmdCode);
+            return -EINVAL;
+    }
+
+    return 0;
+}
+
+int32_t HapticGenerator_GetDescriptor(effect_handle_t self, effect_descriptor_t *descriptor) {
+    HapticGeneratorContext *context = (HapticGeneratorContext *) self;
+
+    if (context == nullptr ||
+        context->state == HAPTICGENERATOR_STATE_UNINITIALIZED) {
+        return -EINVAL;
+    }
+
+    memcpy(descriptor, &gHgDescriptor, sizeof(effect_descriptor_t));
+
+    return 0;
+}
+
+} // namespace android::audio_effect::haptic_generator
diff --git a/media/libeffects/hapticgenerator/EffectHapticGenerator.h b/media/libeffects/hapticgenerator/EffectHapticGenerator.h
new file mode 100644
index 0000000..4a2308b
--- /dev/null
+++ b/media/libeffects/hapticgenerator/EffectHapticGenerator.h
@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#ifndef ANDROID_EFFECTHAPTICGENERATOR_H_
+#define ANDROID_EFFECTHAPTICGENERATOR_H_
+
+#include <functional>
+#include <vector>
+
+#include <hardware/audio_effect.h>
+#include <system/audio_effect.h>
+
+#include "Processors.h"
+
+namespace android::audio_effect::haptic_generator {
+
+//-----------------------------------------------------------------------------
+// Definition
+//-----------------------------------------------------------------------------
+
+enum hapticgenerator_state_t {
+    HAPTICGENERATOR_STATE_UNINITIALIZED,
+    HAPTICGENERATOR_STATE_INITIALIZED,
+    HAPTICGENERATOR_STATE_ACTIVE,
+};
+
+// parameters for each haptic generator
+struct HapticGeneratorParam {
+    uint32_t hapticChannelSource[2]; // The audio channels used to generate haptic channels.
+                                     // The first channel will be used to generate HAPTIC_A,
+                                     // The second channel will be used to generate HAPTIC_B
+                                     // The value will be offset of audio channel
+    uint32_t audioChannelCount;
+    uint32_t hapticChannelCount;
+};
+
+// A structure to keep all shared pointers for all processors in HapticGenerator.
+struct HapticGeneratorProcessorsRecord {
+    std::vector<std::shared_ptr<BiquadFilter>> filters;
+    std::vector<std::shared_ptr<Ramp>> ramps;
+    std::vector<std::shared_ptr<SlowEnvelope>> slowEnvs;
+};
+
+// A structure to keep all the context for HapticGenerator.
+struct HapticGeneratorContext {
+    const struct effect_interface_s *itfe;
+    effect_config_t config;
+    hapticgenerator_state_t state;
+    struct HapticGeneratorParam param;
+    size_t audioDataBytesPerFrame;
+
+    // A cache for all shared pointers of the HapticGenerator
+    struct HapticGeneratorProcessorsRecord processorsRecord;
+
+    // Using a vector of functions to record the processing chain for haptic-generating algorithm.
+    // The three parameters of the processing functions are pointer to output buffer, pointer to
+    // input buffer and frame count.
+    std::vector<std::function<void(float*, const float*, size_t)>> processingChain;
+
+    // inputBuffer is where to keep input buffer for the generating algorithm. It will be
+    // constructed according to HapticGeneratorParam.hapticChannelSource.
+    std::vector<float> inputBuffer;
+
+    // outputBuffer is a buffer having the same length as inputBuffer. It can be used as
+    // intermediate buffer in the generating algorithm.
+    std::vector<float> outputBuffer;
+};
+
+//-----------------------------------------------------------------------------
+// Effect API
+//-----------------------------------------------------------------------------
+
+int32_t HapticGeneratorLib_Create(const effect_uuid_t *uuid,
+                                  int32_t sessionId,
+                                  int32_t ioId,
+                                  effect_handle_t *handle);
+
+int32_t HapticGeneratorLib_Release(effect_handle_t handle);
+
+int32_t HapticGeneratorLib_GetDescriptor(const effect_uuid_t *uuid,
+                                         effect_descriptor_t *descriptor);
+
+int32_t HapticGenerator_Process(effect_handle_t self,
+                                audio_buffer_t *inBuffer,
+                                audio_buffer_t *outBuffer);
+
+int32_t HapticGenerator_Command(effect_handle_t self,
+                                uint32_t cmdCode,
+                                uint32_t cmdSize,
+                                void *cmdData,
+                                uint32_t *replySize,
+                                void *replyData);
+
+int32_t HapticGenerator_GetDescriptor(effect_handle_t self,
+                                      effect_descriptor_t *descriptor);
+
+} // namespace android::audio_effect::haptic_generator
+
+#endif // ANDROID_EFFECTHAPTICGENERATOR_H_
diff --git a/media/libeffects/hapticgenerator/MODULE_LICENSE_APACHE2 b/media/libeffects/hapticgenerator/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/media/libeffects/hapticgenerator/MODULE_LICENSE_APACHE2
diff --git a/media/libeffects/hapticgenerator/Processors.cpp b/media/libeffects/hapticgenerator/Processors.cpp
new file mode 100644
index 0000000..179b5dc
--- /dev/null
+++ b/media/libeffects/hapticgenerator/Processors.cpp
@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2020 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 "EffectHG_Processors"
+//#define LOG_NDEBUG 0
+#include <utils/Log.h>
+
+#include <assert.h>
+
+#include <cmath>
+
+#include "Processors.h"
+
+#if defined(__aarch64__) || defined(__ARM_NEON__)
+#ifndef USE_NEON
+#define USE_NEON (true)
+#endif
+#else
+#define USE_NEON (false)
+#endif
+#if USE_NEON
+#include <arm_neon.h>
+#endif
+
+namespace android::audio_effect::haptic_generator {
+
+float getRealPoleZ(float cornerFrequency, float sampleRate) {
+    // This will be a pole of a first order filter.
+    float realPoleS = -2 * M_PI * cornerFrequency;
+    return exp(realPoleS / sampleRate); // zero-pole matching
+}
+
+std::pair<float, float> getComplexPoleZ(float ringingFrequency, float q, float sampleRate) {
+    // This is the pole for 1/(s^2 + s/q + 1) in normalized frequency. The other pole is
+    // the complex conjugate of this.
+    float poleImagS = 2 * M_PI * ringingFrequency;
+    float poleRealS = -poleImagS / (2 * q);
+    float poleRadius = exp(poleRealS / sampleRate);
+    float poleImagZ = poleRadius * sin(poleImagS / sampleRate);
+    float poleRealZ = poleRadius * cos(poleImagS / sampleRate);
+    return {poleRealZ, poleImagZ};
+}
+
+// Implementation of Ramp
+
+Ramp::Ramp(size_t channelCount) : mChannelCount(channelCount) {}
+
+void Ramp::process(float *out, const float *in, size_t frameCount) {
+    size_t i = 0;
+#if USE_NEON
+    size_t sampleCount = frameCount * mChannelCount;
+    float32x2_t allZero = vdup_n_f32(0.0f);
+    while (i + 1 < sampleCount) {
+        vst1_f32(out, vmax_f32(vld1_f32(in), allZero));
+        in += 2;
+        out += 2;
+        i += 2;
+    }
+#endif // USE_NEON
+    for (; i < frameCount * mChannelCount; ++i) {
+        *out = *in >= 0.0f ? *in : 0.0f;
+        out++;
+        in++;
+    }
+}
+
+// Implementation of SlowEnvelope
+
+SlowEnvelope::SlowEnvelope(
+        float cornerFrequency,
+        float sampleRate,
+        float normalizationPower,
+        size_t channelCount)
+        : mLpf(createLPF(cornerFrequency, sampleRate, channelCount)),
+          mNormalizationPower(normalizationPower),
+          mChannelCount(channelCount),
+          mEnv(0.25 * (sampleRate / (2 * M_PI * cornerFrequency))) {}
+
+void SlowEnvelope::process(float* out, const float* in, size_t frameCount) {
+    size_t sampleCount = frameCount * mChannelCount;
+    if (sampleCount > mLpfInBuffer.size()) {
+        mLpfInBuffer.resize(sampleCount, mEnv);
+        mLpfOutBuffer.resize(sampleCount);
+    }
+    mLpf->process(mLpfOutBuffer.data(), mLpfInBuffer.data(), frameCount);
+    for (size_t i = 0; i < sampleCount; ++i) {
+        *out = *in * pow(mLpfOutBuffer[i], mNormalizationPower);
+        out++;
+        in++;
+    }
+}
+
+void SlowEnvelope::clear() {
+    mLpf->clear();
+}
+
+// Implementation of helper functions
+
+BiquadFilterCoefficients cascadeFirstOrderFilters(const BiquadFilterCoefficients &coefs1,
+                                                   const BiquadFilterCoefficients &coefs2) {
+    assert(coefs1[2] == 0.0f);
+    assert(coefs2[2] == 0.0f);
+    assert(coefs1[4] == 0.0f);
+    assert(coefs2[4] == 0.0f);
+    return {coefs1[0] * coefs2[0],
+            coefs1[0] * coefs2[1] + coefs1[1] * coefs2[0],
+            coefs1[1] * coefs2[1],
+            coefs1[3] + coefs2[3],
+            coefs1[3] * coefs2[3]};
+}
+
+BiquadFilterCoefficients lpfCoefs(const float cornerFrequency, const float sampleRate) {
+    BiquadFilterCoefficients coefficient;
+    float realPoleZ = getRealPoleZ(cornerFrequency, sampleRate);
+    // This is a zero at nyquist
+    coefficient[0] = 0.5f * (1 - realPoleZ);
+    coefficient[1] = coefficient[0];
+    coefficient[2] = 0.0f;
+    coefficient[3] = -realPoleZ; // This is traditional 1/(s+1) filter
+    coefficient[4] = 0.0f;
+    return coefficient;
+}
+
+std::shared_ptr<BiquadFilter> createLPF(const float cornerFrequency,
+                                        const float sampleRate,
+                                        const size_t channelCount) {
+    BiquadFilterCoefficients coefficient = lpfCoefs(cornerFrequency, sampleRate);
+    return std::make_shared<BiquadFilter>(channelCount, coefficient);
+}
+
+std::shared_ptr<BiquadFilter> createLPF2(const float cornerFrequency,
+                                         const float sampleRate,
+                                         const size_t channelCount) {
+    BiquadFilterCoefficients coefficient = lpfCoefs(cornerFrequency, sampleRate);
+    return std::make_shared<BiquadFilter>(
+            channelCount, cascadeFirstOrderFilters(coefficient, coefficient));
+}
+
+std::shared_ptr<BiquadFilter> createHPF2(const float cornerFrequency,
+                                         const float sampleRate,
+                                         const size_t channelCount) {
+    BiquadFilterCoefficients coefficient;
+    // Note: this is valid only when corner frequency is less than nyquist / 2.
+    float realPoleZ = getRealPoleZ(cornerFrequency, sampleRate);
+
+    // Note: this is a zero at DC
+    coefficient[0] = 0.5f * (1 + realPoleZ);
+    coefficient[1] = -coefficient[0];
+    coefficient[2] = 0.0f;
+    coefficient[3] = -realPoleZ;
+    coefficient[4] = 0.0f;
+    return std::make_shared<BiquadFilter>(
+            channelCount, cascadeFirstOrderFilters(coefficient, coefficient));
+}
+
+BiquadFilterCoefficients apfCoefs(const float cornerFrequency, const float sampleRate) {
+    BiquadFilterCoefficients coefficient;
+    float realPoleZ = getRealPoleZ(cornerFrequency, sampleRate);
+    float zeroZ = 1.0f / realPoleZ;
+    coefficient[0] = (1.0f - realPoleZ) / (1.0f - zeroZ);
+    coefficient[1] = -coefficient[0] * zeroZ;
+    coefficient[2] = 0.0f;
+    coefficient[3] = -realPoleZ;
+    coefficient[4] = 0.0f;
+    return coefficient;
+}
+
+std::shared_ptr<BiquadFilter> createAPF(const float cornerFrequency,
+                                        const float sampleRate,
+                                        const size_t channelCount) {
+    BiquadFilterCoefficients coefficient = apfCoefs(cornerFrequency, sampleRate);
+    return std::make_shared<BiquadFilter>(channelCount, coefficient);
+}
+
+std::shared_ptr<BiquadFilter> createAPF2(const float cornerFrequency1,
+                                         const float cornerFrequency2,
+                                         const float sampleRate,
+                                         const size_t channelCount) {
+    BiquadFilterCoefficients coefs1 = apfCoefs(cornerFrequency1, sampleRate);
+    BiquadFilterCoefficients coefs2 = apfCoefs(cornerFrequency2, sampleRate);
+    return std::make_shared<BiquadFilter>(
+            channelCount, cascadeFirstOrderFilters(coefs1, coefs2));
+}
+
+std::shared_ptr<BiquadFilter> createBPF(const float ringingFrequency,
+                                        const float q,
+                                        const float sampleRate,
+                                        const size_t channelCount) {
+    BiquadFilterCoefficients coefficient;
+    const auto [real, img] = getComplexPoleZ(ringingFrequency, q, sampleRate);
+    // Note: this is not a standard cookbook BPF, but a low pass filter with zero at DC
+    coefficient[0] = 1.0f;
+    coefficient[1] = -1.0f;
+    coefficient[2] = 0.0f;
+    coefficient[3] = -2 * real;
+    coefficient[4] = real * real + img * img;
+    return std::make_shared<BiquadFilter>(channelCount, coefficient);
+}
+
+std::shared_ptr<BiquadFilter> createBSF(const float ringingFrequency,
+                                        const float zq,
+                                        const float pq,
+                                        const float sampleRate,
+                                        const size_t channelCount) {
+    BiquadFilterCoefficients coefficient;
+    const auto [zeroReal, zeroImg] = getComplexPoleZ(ringingFrequency, zq, sampleRate);
+    float zeroCoeff1 = -2 * zeroReal;
+    float zeroCoeff2 = zeroReal* zeroReal + zeroImg * zeroImg;
+    const auto [poleReal, poleImg] = getComplexPoleZ(ringingFrequency, pq, sampleRate);
+    float poleCoeff1 = -2 * poleReal;
+    float poleCoeff2 = poleReal * poleReal + poleImg * poleImg;
+    const float norm = (1.0f + poleCoeff1 + poleCoeff2) / (1.0f + zeroCoeff1 + zeroCoeff2);
+    coefficient[0] = 1.0f * norm;
+    coefficient[1] = zeroCoeff1 * norm;
+    coefficient[2] = zeroCoeff2 * norm;
+    coefficient[3] = poleCoeff1;
+    coefficient[4] = poleCoeff2;
+    return std::make_shared<BiquadFilter>(channelCount, coefficient);
+}
+
+} // namespace android::audio_effect::haptic_generator
diff --git a/media/libeffects/hapticgenerator/Processors.h b/media/libeffects/hapticgenerator/Processors.h
new file mode 100644
index 0000000..e14458b
--- /dev/null
+++ b/media/libeffects/hapticgenerator/Processors.h
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#ifndef _EFFECT_HAPTIC_GENERATOR_PROCESSORS_H_
+#define _EFFECT_HAPTIC_GENERATOR_PROCESSORS_H_
+
+#include <sys/types.h>
+
+#include <memory>
+#include <vector>
+
+#include <audio_utils/BiquadFilter.h>
+
+using android::audio_utils::BiquadFilter;
+using BiquadFilterCoefficients = std::array<float, android::audio_utils::kBiquadNumCoefs>;
+
+namespace android::audio_effect::haptic_generator {
+
+// A class providing a process function that makes input data non-negative.
+class Ramp {
+public:
+    explicit Ramp(size_t channelCount);
+
+    void process(float *out, const float *in, size_t frameCount);
+
+private:
+    const size_t mChannelCount;
+};
+
+
+class SlowEnvelope {
+public:
+    SlowEnvelope(float cornerFrequency, float sampleRate,
+                 float normalizationPower, size_t channelCount);
+
+    void process(float *out, const float *in, size_t frameCount);
+
+    void clear();
+
+private:
+    const std::shared_ptr<BiquadFilter> mLpf;
+    std::vector<float> mLpfInBuffer;
+    std::vector<float> mLpfOutBuffer;
+    const float mNormalizationPower;
+    const float mChannelCount;
+    const float mEnv;
+};
+
+// Helper functions
+
+BiquadFilterCoefficients cascadeFirstOrderFilters(const BiquadFilterCoefficients &coefs1,
+                                                  const BiquadFilterCoefficients &coefs2);
+
+std::shared_ptr<BiquadFilter> createLPF(const float cornerFrequency,
+                                        const float sampleRate,
+                                        const size_t channelCount);
+
+// Create two cascaded LPF with same corner frequency.
+std::shared_ptr<BiquadFilter> createLPF2(const float cornerFrequency,
+                                         const float sampleRate,
+                                         const size_t channelCount);
+
+// Create two cascaded HPF with same corner frequency.
+std::shared_ptr<BiquadFilter> createHPF2(const float cornerFrequency,
+                                         const float sampleRate,
+                                         const size_t channelCount);
+
+std::shared_ptr<BiquadFilter> createAPF(const float cornerFrequency,
+                                        const float sampleRate,
+                                        const size_t channelCount);
+
+// Create two cascaded APF with two different corner frequency.
+std::shared_ptr<BiquadFilter> createAPF2(const float cornerFrequency1,
+                                         const float cornerFrequency2,
+                                         const float sampleRate,
+                                         const size_t channelCount);
+
+std::shared_ptr<BiquadFilter> createBPF(const float ringingFrequency,
+                                        const float q,
+                                        const float sampleRate,
+                                        const size_t channelCount);
+
+std::shared_ptr<BiquadFilter> createBSF(const float ringingFrequency,
+                                        const float zq,
+                                        const float pq,
+                                        const float sampleRate,
+                                        const size_t channelCount);
+
+} // namespace android::audio_effect::haptic_generator
+
+#endif // _EFFECT_HAPTIC_GENERATOR_PROCESSORS_H_