Android-video-视频软硬件编解码器的集成

　安卓机器中都有很多视频软硬件编解码器，例如: h264/hevc/h263/mpeg4……等等。但是如果现在有一个新的符合标准的编码器给你，需要怎么集成呢？阅读本文你将会找到答案。

1. 软件编码器的集成:

　　集成之前需要先了解软件编码器的加载过程:

1.1 软件编码器的加载过程

// frameworks/av/media/libstagefright/ACodec.cpp
step1: ACodec收到消息kWhatAllocateComponent或者在onSetup的时候就会调用onAllocateComponent。step2: ACodec调用omx去创建组件
bool ACodec::UninitializedState::onAllocateComponent(const sp &msg) {ALOGV("onAllocateComponent");CHECK(mCodec->mOMXNode == NULL);sp notify = new AMessage(kWhatOMXDied, mCodec);sp obj;CHECK(msg->findObject("codecInfo", &obj));sp info = (MediaCodecInfo *)obj.get(); // 获取codec信息AString owner = "default";AString componentName;CHECK(msg->findString("componentName", &componentName)); // 获取componentName//　确认使用的是平台的codecif (!(componentName.find("qcom", 0) > 0 || componentName.find("qti", 0) > 0) ||componentName.find("video", 0) > 0 || componentName.find("flac", 0) > 0) {if (info == nullptr) {ALOGE("Unexpected nullptr for codec information");mCodec->signalError(OMX_ErrorUndefined, UNKNOWN_ERROR);return false;}owner = (info->getOwnerName() == nullptr) ? "default" : info->getOwnerName();}sp observer = new CodecObserver; // 创建CodecObserversp omx;sp omxNode;status_t err = NAME_NOT_FOUND;OMXClient client;if (client.connect(owner.c_str()) != OK) { // 能否找到对应的codecmCodec->signalError(OMX_ErrorUndefined, NO_INIT);return false;}omx = client.interface(); // 给omx赋值???pid_t tid = gettid();int prevPriority = androidGetThreadPriority(tid);androidSetThreadPriority(tid, ANDROID_PRIORITY_FOREGROUND); // 设置线程优先级err = omx->allocateNode(componentName.c_str(), observer, &omxNode); // 调用allocateNode，把CodecObserver和omxNode联系起来androidSetThreadPriority(tid, prevPriority); //　线程优先级恢复if (err != OK) {ALOGE("Unable to instantiate codec '%s' with err %#x.", componentName.c_str(), err);mCodec->signalError((OMX_ERRORTYPE)err, makeNoSideEffectStatus(err));return false;}mDeathNotifier = new DeathNotifier(notify); // mDeathNotifier的作用？？？auto tOmxNode = omxNode->getHalInterface();if (!tOmxNode->linkToDeath(mDeathNotifier, 0)) {mDeathNotifier.clear();}notify = new AMessage(kWhatOMXMessageList, mCodec);notify->setInt32("generation", ++mCodec->mNodeGeneration);observer->setNotificationMessage(notify);mCodec->mComponentName = componentName;mCodec->mRenderTracker.setComponentName(componentName);mCodec->mFlags = 0;if (componentName.endsWith(".secure")) {mCodec->mFlags |= kFlagIsSecure;mCodec->mFlags |= kFlagIsGrallocUsageProtected;mCodec->mFlags |= kFlagPushBlankBuffersToNativeWindowOnShutdown;}mCodec->mOMX = omx;mCodec->mOMXNode = omxNode;mCodec->mCallback->onComponentAllocated(mCodec->mComponentName.c_str());mCodec->changeState(mCodec->mLoadedState);return true;
}// frameworks/av/media/libstagefright/omx/1.0/Omx.cpp
Return Omx::allocateNode(const hidl_string& name,const sp& observer,allocateNode_cb _hidl_cb) {using ::android::IOMXNode;using ::android::IOMXObserver;sp instance;{Mutex::Autolock autoLock(mLock);if (mLiveNodes.size() == kMaxNodeInstances) {..... // 处理异常}instance = new OMXNodeInstance( // 新建OMXNodeInstancethis, new LWOmxObserver(observer), name.c_str());OMX_COMPONENTTYPE *handle;// 调用OMXMaster的makeComponentInstanceOMX_ERRORTYPE err = mMaster->makeComponentInstance(name.c_str(), &OMXNodeInstance::kCallbacks,instance.get(), &handle);if (err != OMX_ErrorNone) {.....　// 处理异常}instance->setHandle(handle); // setHandle// Find quirks from mParserconst auto& codec = mParser.getCodecMap().find(name.c_str());if (codec == mParser.getCodecMap().cend()) {LOG(WARNING) << "Failed to obtain quirks for omx component ""'" << name.c_str() << "' ""from XML files";} else {uint32_t quirks = 0;for (const auto& quirk : codec->second.quirkSet) {if (quirk == "requires-allocate-on-input-ports") {quirks |= OMXNodeInstance::kRequiresAllocateBufferOnInputPorts;}if (quirk == "requires-allocate-on-output-ports") {quirks |= OMXNodeInstance::kRequiresAllocateBufferOnOutputPorts;}}instance->setQuirks(quirks);}mLiveNodes.add(observer.get(), instance);mNode2Observer.add(instance.get(), observer.get());}observer->linkToDeath(this, 0);_hidl_cb(toStatus(OK), new TWOmxNode(instance));return Void();
}// frameworks/av/media/libstagefright/omx/OMXMaster.cpp
OMX_ERRORTYPE OMXMaster::makeComponentInstance(const char *name,const OMX_CALLBACKTYPE *callbacks,OMX_PTR appData,OMX_COMPONENTTYPE **component) {ALOGI("makeComponentInstance(%s) in %s process", name, mProcessName);Mutex::Autolock autoLock(mLock);*component = NULL;ssize_t index = mPluginByComponentName.indexOfKey(String8(name));if (index < 0) {return OMX_ErrorInvalidComponentName;}OMXPluginBase *plugin = mPluginByComponentName.valueAt(index);// 如果是软件编解码器，调用SoftOMXPlugin的makeComponentInstance,如果是硬件就调用QComOMXPlugin的makeComponentInstance。OMX_ERRORTYPE err =plugin->makeComponentInstance(name, callbacks, appData, component);if (err != OMX_ErrorNone) {return err;}mPluginByInstance.add(*component, plugin);return err;
}// frameworks/av/media/libstagefright/omx/SoftOMXPlugin.cpp
OMX_ERRORTYPE SoftOMXPlugin::makeComponentInstance(const char *name,const OMX_CALLBACKTYPE *callbacks,OMX_PTR appData,OMX_COMPONENTTYPE **component) {ALOGV("makeComponentInstance '%s'", name);for (size_t i = 0; i < kNumComponents; ++i) {if (strcmp(name, kComponents[i].mName)) {continue;}　// 此处是根据名字在kComponents中循环去找到匹配的编解码器AString libName = "libstagefright_soft_";　// 编解码器name补全libName.append(kComponents[i].mLibNameSuffix);libName.append(".so");// dlopen打开编解码器void *libHandle = dlopen(libName.c_str(), RTLD_NOW|RTLD_NODELETE);if (libHandle == NULL) {ALOGE("unable to dlopen %s: %s", libName.c_str(), dlerror());return OMX_ErrorComponentNotFound;}typedef SoftOMXComponent *(*CreateSoftOMXComponentFunc)(const char *, const OMX_CALLBACKTYPE *,OMX_PTR, OMX_COMPONENTTYPE **);CreateSoftOMXComponentFunc createSoftOMXComponent =(CreateSoftOMXComponentFunc)dlsym(libHandle,"_Z22createSoftOMXComponentPKcPK16OMX_CALLBACKTYPE""PvPP17OMX_COMPONENTTYPE");if (createSoftOMXComponent == NULL) {dlclose(libHandle);libHandle = NULL;return OMX_ErrorComponentNotFound;}sp codec =(*createSoftOMXComponent)(name, callbacks, appData, component);if (codec == NULL) {dlclose(libHandle);libHandle = NULL;return OMX_ErrorInsufficientResources;}OMX_ERRORTYPE err = codec->initCheck();if (err != OMX_ErrorNone) {dlclose(libHandle);libHandle = NULL;return err;}codec->incStrong(this);codec->setLibHandle(libHandle);return OMX_ErrorNone;}return OMX_ErrorInvalidComponentName;
}

从上面的过程来看，最终就是根据软件编码器的name来加载的，在SoftOMXPlugin中首先根据codec name在kComponents中寻找对应的编解码器的名字，然后补齐即可。

kComponents内容如下:

static const struct {const char *mName;const char *mLibNameSuffix;const char *mRole;} kComponents[] = {// two choices for aac decoding.// configurable in media/libstagefright/data/media_codecs_google_audio.xml// default implementation{ "OMX.google.aac.decoder", "aacdec", "audio_decoder.aac" },// alternate implementation{ "OMX.google.xaac.decoder", "xaacdec", "audio_decoder.aac" },{ "OMX.google.aac.encoder", "aacenc", "audio_encoder.aac" },{ "OMX.google.amrnb.decoder", "amrdec", "audio_decoder.amrnb" },{ "OMX.google.amrnb.encoder", "amrnbenc", "audio_encoder.amrnb" },{ "OMX.google.amrwb.decoder", "amrdec", "audio_decoder.amrwb" },{ "OMX.google.amrwb.encoder", "amrwbenc", "audio_encoder.amrwb" },{ "OMX.google.h264.decoder", "avcdec", "video_decoder.avc" },{ "OMX.google.h264.encoder", "avcenc", "video_encoder.avc" },{ "OMX.google.hevc.decoder", "hevcdec", "video_decoder.hevc" },{ "OMX.google.g711.alaw.decoder", "g711dec", "audio_decoder.g711alaw" },{ "OMX.google.g711.mlaw.decoder", "g711dec", "audio_decoder.g711mlaw" },{ "OMX.google.mpeg2.decoder", "mpeg2dec", "video_decoder.mpeg2" },{ "OMX.google.h263.decoder", "mpeg4dec", "video_decoder.h263" },{ "OMX.google.h263.encoder", "mpeg4enc", "video_encoder.h263" },{ "OMX.google.mpeg4.decoder", "mpeg4dec", "video_decoder.mpeg4" },{ "OMX.google.mpeg4.encoder", "mpeg4enc", "video_encoder.mpeg4" },{ "OMX.google.mp3.decoder", "mp3dec", "audio_decoder.mp3" },{ "OMX.google.vorbis.decoder", "vorbisdec", "audio_decoder.vorbis" },{ "OMX.google.opus.decoder", "opusdec", "audio_decoder.opus" },{ "OMX.google.vp8.decoder", "vpxdec", "video_decoder.vp8" },{ "OMX.google.vp9.decoder", "vpxdec", "video_decoder.vp9" },{ "OMX.google.vp8.encoder", "vpxenc", "video_encoder.vp8" },{ "OMX.google.vp9.encoder", "vpxenc", "video_encoder.vp9" },{ "OMX.google.raw.decoder", "rawdec", "audio_decoder.raw" },{ "OMX.google.flac.decoder", "flacdec", "audio_decoder.flac" },{ "OMX.google.flac.encoder", "flacenc", "audio_encoder.flac" },{ "OMX.google.gsm.decoder", "gsmdec", "audio_decoder.gsm" },
#ifdef QTI_FLAC_DECODER{ "OMX.qti.audio.decoder.flac", "qtiflacdec", "audio_decoder.flac" },
#endif
};

1.2 软件编解码器的集成

　　看懂了上面的加载过程，集成就特别简单了。

　　step1: 我们的编解码器需要符合统一命名规则，即libstagefright_soft_xxx.so的格式。

　　step2: 把mLibNameSuffix即xxx对应的内容添加到kComponents中。(例如我们需要把"OMX.google.h264.encoder"对应的编码器改为libstagefright_soft_xxx.so则只需把kComponents的:{ "OMX.google.h264.encoder", "avcenc", "video_encoder.avc" },改为

{ "OMX.google.h264.encoder", "xxx", "video_encoder.avc" },)

　　step3: 重编libstagefright_omx.so，并将其push到system/lib system/lib/vndk-28 system/lib64 system/lib64/vndk-28 vendor/lib/vndk vendor/lib64/vndk目录下。

　　step4: 把需要替换的libstagefright_soft_xxx.so放到vendor/lib和vendor/lib64下。

　　step5: reboot之后即可使用。

2. 硬件编解码器的集成

　　上面介绍了软件编解码器的集成，实际从acodec到OmxMaster部分软硬件都是相同的，只是在plugin时软件使用的SoftOMXPlugin，硬件使用QComOMXPlugin。

2.1 硬解编解码器的plugin

// hardware/qcom/media/libstagefrighthw/QComOMXPlugin.cpp
OMX_ERRORTYPE QComOMXPlugin::makeComponentInstance(const char *name,const OMX_CALLBACKTYPE *callbacks,OMX_PTR appData,OMX_COMPONENTTYPE **component) {if (mLibHandle == NULL) { // 此处mLibHandle在结构体构造时就赋值dlopen("libOmxCore.so", RTLD_NOW)return OMX_ErrorUndefined;}return (*mGetHandle)( // mGetHandle = (GetHandleFunc)dlsym(mLibHandle, "OMX_GetHandle");
// 也就是mGetHandle对应的实现在libOmxCore.so的OMX_GetHandle这个函数。reinterpret_cast(component),const_cast(name),appData, const_cast(callbacks));
}// /hardware/qcom/media/mm-core/src/common/qc_omx_core.c
OMX_API OMX_ERRORTYPE OMX_APIENTRY
OMX_GetHandle(OMX_OUT OMX_HANDLETYPE*     handle,OMX_IN OMX_STRING    componentName,OMX_IN OMX_PTR             appData,OMX_IN OMX_CALLBACKTYPE* callBacks)
{OMX_ERRORTYPE  eRet = OMX_ErrorNone;int cmp_index = -1;int hnd_index = -1;int vpp_cmp_index = -1;pthread_mutex_lock(&lock_core);if(handle){*handle = NULL;char optComponentName[OMX_MAX_STRINGNAME_SIZE];strlcpy(optComponentName, componentName, OMX_MAX_STRINGNAME_SIZE);// 把componentName赋值给optComponentNameif(strstr(componentName, "avc") && strstr(componentName, "decoder")){　// 如果是avc decoder，需要判断是否有dsmodevoid *libhandle = dlopen("libOmxVideoDSMode.so", RTLD_NOW);if(libhandle){int (*fn_ptr)()  = dlsym(libhandle, "isDSModeActive");if(fn_ptr == NULL){DEBUG_PRINT_ERROR("Error: isDSModeActive Not Found %s\n",dlerror());}else{int isActive = fn_ptr();char *pSubString = strstr(componentName, ".dsmode");if(pSubString){optComponentName[pSubString - componentName] = 0;}else if(isActive){strlcat(optComponentName, ".dsmode", OMX_MAX_STRINGNAME_SIZE);}cmp_index = get_cmp_index(optComponentName);}dlclose(libhandle);}else{DEBUG_PRINT_ERROR("Failed to load dsmode library");}}if(cmp_index < 0) { // 先通过componentName找到cmp_index，在把componentName赋值给optComponentName。cmp_index = get_cmp_index(componentName);strlcpy(optComponentName, componentName, OMX_MAX_STRINGNAME_SIZE);}if(cmp_index >= 0){DEBUG_PRINT("getting fn pointer\n");// Load VPP omx component for decoder if vpp property is enabledconst char *hwDecLib = "libOmxVdec.so";　　// 硬件解码const char *swDecLib = "libOmxSwVdec.so";　// 软件解码if (!strncmp(core[cmp_index].so_lib_name, hwDecLib, strlen(hwDecLib)) ||!strncmp(core[cmp_index].so_lib_name, swDecLib, strlen(swDecLib))) {　// 找到了当前component对应的lib库bool isVppEnabled = false;if (isConfigStoreEnabled()) {getConfigStoreBool("vpp", "enable", &isVppEnabled, false);} else {char value[PROPERTY_VALUE_MAX];if ((property_get("vendor.media.vpp.enable", value, NULL))&& (!strcmp("1", value) || !strcmp("true", value))) {isVppEnabled = true;}}if (isVppEnabled) {　// 如果enable了vppDEBUG_PRINT("VPP property is enabled");vpp_cmp_index = get_cmp_index("OMX.qti.vdec.vpp");if (vpp_cmp_index < 0) {DEBUG_PRINT_ERROR("Unable to find VPP OMX lib in registry ");} else {DEBUG_PRINT("Loading vpp for vdec");cmp_index = vpp_cmp_index;}}}// 动态加载so库core[cmp_index].fn_ptr =omx_core_load_cmp_library(core[cmp_index].so_lib_name,&core[cmp_index].so_lib_handle);if(core[cmp_index].fn_ptr){void* pThis = (*(core[cmp_index].fn_ptr))();if(pThis){void *hComp = NULL;hComp = qc_omx_create_component_wrapper((OMX_PTR)pThis);// 创建hComp，hComp实际指向pThis->m_cmp，可用hComp调用OMX_COMPONENTTYPE里面的各种函数。if((eRet = qc_omx_component_init(hComp, optComponentName)) !=OMX_ErrorNone)　// 初始化{DEBUG_PRINT("Component not created succesfully\n");pthread_mutex_unlock(&lock_core);return eRet;}qc_omx_component_set_callbacks(hComp,callBacks,appData); // 设置callBacksif (vpp_cmp_index >= 0){hnd_index = get_comp_handle_index("OMX.qti.vdec.vpp");　// get_comp_handle_index}else{hnd_index = get_comp_handle_index(optComponentName);}if(hnd_index >= 0){core[cmp_index].inst[hnd_index]= *handle = (OMX_HANDLETYPE) hComp;}else{DEBUG_PRINT("OMX_GetHandle:NO free slot available to store Component Handle\n");pthread_mutex_unlock(&lock_core);return OMX_ErrorInsufficientResources;}DEBUG_PRINT("Component %p Successfully created\n",*handle);}else{eRet = OMX_ErrorInsufficientResources;DEBUG_PRINT("Component Creation failed\n");}}else{eRet = OMX_ErrorNotImplemented;DEBUG_PRINT("library couldnt return create instance fn\n");}}else{eRet = OMX_ErrorNotImplemented;DEBUG_PRINT("ERROR: Already another instance active  ;rejecting \n");}}else{eRet =  OMX_ErrorBadParameter;DEBUG_PRINT("\n OMX_GetHandle: NULL handle \n");}pthread_mutex_unlock(&lock_core);return eRet;
}

上面介绍了component的注册过程，下面仔细看看每个函数的实现

// hardware/qcom/media/mm-core/src/common/omx_core_cmp.cpp
void * qc_omx_create_component_wrapper(OMX_PTR obj_ptr)
{qc_omx_component *pThis        = (qc_omx_component *)obj_ptr;OMX_COMPONENTTYPE* component   = &(pThis->m_cmp);memset(&pThis->m_cmp,0,sizeof(OMX_COMPONENTTYPE));component->nSize               = sizeof(OMX_COMPONENTTYPE);component->nVersion.nVersion   = OMX_SPEC_VERSION;component->pApplicationPrivate = 0;component->pComponentPrivate   = obj_ptr;component->AllocateBuffer      = &qc_omx_component_allocate_buffer;component->FreeBuffer          = &qc_omx_component_free_buffer;component->GetParameter        = &qc_omx_component_get_parameter;component->SetParameter        = &qc_omx_component_set_parameter;component->SendCommand         = &qc_omx_component_send_command;component->FillThisBuffer      = &qc_omx_component_fill_this_buffer;component->EmptyThisBuffer     = &qc_omx_component_empty_this_buffer;component->GetState            = &qc_omx_component_get_state;component->GetComponentVersion = &qc_omx_component_get_version;component->GetConfig           = &qc_omx_component_get_config;component->SetConfig           = &qc_omx_component_set_config;component->GetExtensionIndex   = &qc_omx_component_get_extension_index;component->ComponentTunnelRequest = &qc_omx_component_tunnel_request;component->UseBuffer           = &qc_omx_component_use_buffer;component->SetCallbacks        = &qc_omx_component_set_callbacks;component->UseEGLImage         = &qc_omx_component_use_EGL_image;component->ComponentRoleEnum   = &qc_omx_component_role_enum;component->ComponentDeInit     = &qc_omx_component_deinit;return (void *)component;
}OMX_ERRORTYPE
qc_omx_component_init(OMX_IN OMX_HANDLETYPE hComp, OMX_IN OMX_STRING componentName)
{OMX_ERRORTYPE eRet = OMX_ErrorBadParameter;qc_omx_component *pThis = (hComp)? (qc_omx_component *)(((OMX_COMPONENTTYPE *)hComp)->pComponentPrivate):NULL;DEBUG_PRINT("OMXCORE: qc_omx_component_init %p\n", hComp);if(pThis){// call the init fuctioneRet = pThis->component_init(componentName); // 此处就会调用omx_vdec_v4l2.cpp里面的omx_vdec::component_init函数。后面的函数都一样，最终都会调用omx_vdec_v4l2.cpp里面对应的函数。if(eRet != OMX_ErrorNone){//  in case of error, please destruct the component createddelete pThis;}}return eRet;
}

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