鸿蒙5.0实战案例：基于OpenGL渲染视频画面帧

往期推文全新看点（文中附带全新鸿蒙5.0全栈学习笔录）

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✏️ 记录一场鸿蒙开发岗位面试经历~

✏️ 持续更新中......

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场景描述

在直播场景中，会有礼物、魔法等表情临时出现在画面，需要获取视频画面帧进行纹理更新后再渲染

通过OpenGL渲染视频画面帧。

⦁ 在ArkTS侧调用createAVPlayer()创建AVPlayer实例，初始化进入idle状态。设置业务需要的监听事件，设置资源：设置属性url，AVPlayer进入initialized状态。

⦁ 设置窗口：获取并设置属性SurfaceID，该surfaceId是native侧nativeImage的surfaceID，调用play方法开始播放。

⦁ 添加XComponent组件，在native侧通过OH_NativeXComponent_RegisterCallback注册XComponent回调。

⦁ 在napi 接口init的时候在Xcomponent的OnSurfaceCreatedCB回调中初始化渲染线程，通过OH_NativeImage_Create创建nativeImage。

⦁ 通过OH_NativeImage_GetSurfaceId获取surfaceID并传递到arkts侧。

⦁ 通过OH_NativeImage_SetOnFrameAvailableListener设置帧可用回调，通过NativeVsync接收系统信号，控制渲染。

⦁ 通过OH_NativeImage_UpdateSurfaceImage获取最新帧更新相关联的OpenGL ES纹理，通过eglSwapBuffers将纹理渲染上屏。

核心代码

创建nativeImage，获取nativeImage的id，设置帧可用回调。

bool RenderThread::CreateNativeImage() 
{ 
  nativeImage_ = OH_NativeImage_Create(-1, GL_TEXTURE_EXTERNAL_OES); 
  if (nativeImage_ == nullptr) { 
    OH_LOG_Print(LOG_APP, LOG_ERROR, LOG_PRINT_DOMAIN, "RenderThread", "OH_NativeImage_Create failed."); 
    return false; 
  } 
  int ret = 0; 
  { 
    std::lock_guard<std::mutex> lock(nativeImageSurfaceIdMutex_); 
    ret = OH_NativeImage_GetSurfaceId(nativeImage_, &nativeImageSurfaceId_); 
  } 
  if (ret != 0) { 
    OH_LOG_Print(LOG_APP, LOG_ERROR, LOG_PRINT_DOMAIN, "RenderThread", 
      "OH_NativeImage_GetSurfaceId failed, ret is %{public}d.", ret); 
    return false; 
  } 
  nativeImageFrameAvailableListener_.context = this; 
  nativeImageFrameAvailableListener_.onFrameAvailable = &RenderThread::OnNativeImageFrameAvailable; 
  ret = OH_NativeImage_SetOnFrameAvailableListener(nativeImage_, nativeImageFrameAvailableListener_); 
  if (ret != 0) { 
    OH_LOG_Print(LOG_APP, LOG_ERROR, LOG_PRINT_DOMAIN, "RenderThread", 
      "OH_NativeImage_SetOnFrameAvailableListener failed, ret is %{public}d.", ret); 
    return false; 
  } 
  return true; 
} 
void RenderThread::OnNativeImageFrameAvailable(void *data) 
{ 
  OH_LOG_Print(LOG_APP, LOG_DEBUG, LOG_PRINT_DOMAIN, "RenderThread", "OnNativeImageFrameAvailable."); 
  auto renderThread = reinterpret_cast<RenderThread *>(data); 
  if (renderThread == nullptr) { 
    return; 
  } 
  renderThread->availableFrameCnt_++; 
  renderThread->wakeUpCond_.notify_one(); 
}
NativeVsync接收系统发送的Vsync信号，控制渲染节奏。
bool RenderThread::InitNativeVsync() 
{ 
  nativeVsync_ = OH_NativeVSync_Create(DEMO_NAME, strlen(DEMO_NAME)); 
  if (nativeVsync_ == nullptr) { 
    OH_LOG_Print(LOG_APP, LOG_ERROR, LOG_PRINT_DOMAIN, "RenderThread", "Create NativeVSync failed."); 
    return false; 
  } 
  (void)OH_NativeVSync_RequestFrame(nativeVsync_, &RenderThread::OnVsync, this); 
  return true; 
} 
void RenderThread::OnVsync(long long timestamp, void *data) 
{ 
  OH_LOG_Print(LOG_APP, LOG_DEBUG, LOG_PRINT_DOMAIN, "RenderThread", "OnVsync %{public}llu.", timestamp); 
  auto renderThread = reinterpret_cast<RenderThread *>(data); 
  if (renderThread == nullptr) { 
    return; 
  } 
  renderThread->vSyncCnt_++; 
  renderThread->wakeUpCond_.notify_one(); 
}

在渲染线程中更新画面帧数据到OpenGL纹理，并做对应的opengl处理后，通过SwapBuffers()方法上屏。

void RenderThread::DrawImage() 
{ 
  if(nativeImageTexId_ == 9999) { 
    glGenTextures(1, &nativeImageTexId_); 
    glBindTexture(GL_TEXTURE_EXTERNAL_OES, nativeImageTexId_); 
    // set the texture wrapping parameters 
    glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_S, GL_REPEAT); 
    glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_WRAP_T, GL_REPEAT); 
    // set texture filtering parameters 
    glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
    glTexParameteri(GL_TEXTURE_EXTERNAL_OES, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
  } 
  OH_LOG_Print(LOG_APP, LOG_DEBUG, LOG_PRINT_DOMAIN, "RenderThread", "DrawImage."); 
  if (eglSurface_ == EGL_NO_SURFACE) { 
    OH_LOG_Print(LOG_APP, LOG_WARN, LOG_PRINT_DOMAIN, "RenderThread", "eglSurface_ is EGL_NO_SURFACE"); 
    return; 
  } 
  OH_NativeImage_AttachContext(nativeImage_, nativeImageTexId_); 
  renderContext_->MakeCurrent(eglSurface_); 
  int32_t ret = OH_NativeImage_UpdateSurfaceImage(nativeImage_); 
  if (ret != 0) { 
    OH_LOG_Print(LOG_APP, LOG_ERROR, LOG_PRINT_DOMAIN, "RenderThread", 
      "OH_NativeImage_UpdateSurfaceImage failed, ret: %{public}d, texId: %{public}d", 
      ret, nativeImageTexId_); 
    return; 
  } 
  OH_LOG_Print(LOG_APP, LOG_DEBUG, LOG_PRINT_DOMAIN, "RenderThread", "OH_NativeImage_UpdateSurfaceImage succeed."); 
  float matrix[16]; 
  ret = OH_NativeImage_GetTransformMatrix(nativeImage_, matrix); 
  if (ret != 0) { 
    OH_LOG_Print(LOG_APP, LOG_ERROR, LOG_PRINT_DOMAIN, "RenderThread", 
      "OH_NativeImage_GetTransformMatrix failed, ret: %{public}d", ret); 
    return; 
  } 
  glClearColor(1.0f, 1.0f, 1.0f, 1.0f); 
  glClear(GL_COLOR_BUFFER_BIT); 
  shaderProgram_->Use(); 
  shaderProgram_->SetInt("texture", 0); 
  glActiveTexture(GL_TEXTURE0); 
  glBindTexture(GL_TEXTURE_EXTERNAL_OES, nativeImageTexId_); 
  shaderProgram_->SetMatrix4v("matTransform", matrix, 16, false); 
  glBindVertexArray(vertexArrayObject_); 
  glEnable(GL_DEPTH_TEST); 
  glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, Detail::indices); 
  renderContext_->SwapBuffers(eglSurface_); 
}