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本篇文章为大家展示了FFmpeg + OpenGLES怎么实现视频解码播放和视频滤镜,内容简明扼要并且容易理解,绝对能使你眼前一亮,通过这篇文章的详细介绍希望你能有所收获。
当你想为播放器做一些视频滤镜时,如加水印、旋转缩放等效果,使用 OpenGL ES 实现起来就极为方便。
经过上面几节的介绍,我们对音视频的解码过程已经比较熟悉了。本文要用 OpenGL 实现视频的渲染,这里再回顾下视频的解码流程:
从流程图中可以看出,解码一帧图像后,首先将对图像进行格式转换,转换成 RGBA 格式,使用 OpenGL 或 ANativeWindow 可以直接进行渲染。
当然,使用 OpenGL 进行渲染时,为了提升性能,可以将格式转换放到 GPU 上来做(即 shader 实现 YUV 到 RGB 的转换),也可以使用 OES 纹理直接接收 YUV 图像数据,这里就不进行展开讲了。
了解视频解码到渲染的流程之后,我们就可以构建 OpenGL 渲染环境。从之前介绍 EGL 的文章中,我们知道在使用 OpenGL API 之前,必须要先利用 EGL 创建好 OpenGL 的渲染上下文环境。至于 EGL 怎么使用,可以参考文章OpenGLES 与 EGL 的关系。
由于本文是面向初学者快速上手 FFmpeg 开发,我们直接利用 Android GLSurfaceView 类创建 OpenGL 渲染环境,GLSurfaceView 类已经封装了 EGL 创建渲染上下文的操作,并启动了一个独立的渲染线程,完全符合我们渲染视频解码帧的需求。
实际上,GLSurfaceView 类在生产开发中可以满足绝大多数的屏幕渲染场景,一般要实现多线程渲染的时候才需要我们单独操作 EGL 的接口。
那么,你肯定会有疑问:GLSurfaceView 是 Java 的类,难道要将 Native 层解码后的视频图像传到 Java 层再进行渲染吗?大可不必,我们只需要将 Java 层的调用栈通过 JNI 延伸到 Native 层即可。
GLSurfaceView 类 Renderer 接口对应渲染的三个关键函数,我们通过 JNI 延伸到 Native 层:
@Override public void onSurfaceCreated(GL10 gl10, EGLConfig eglConfig) { FFMediaPlayer.native_OnSurfaceCreated(); } @Override public void onSurfaceChanged(GL10 gl10, int w, int h) { FFMediaPlayer.native_OnSurfaceChanged(w, h); } @Override public void onDrawFrame(GL10 gl10) { FFMediaPlayer.native_OnDrawFrame(); } //for video openGL render public static native void native_OnSurfaceCreated(); public static native void native_OnSurfaceChanged(int width, int height); public static native void native_OnDrawFrame();
然后,我们在 Native 层创建一个 OpenGLRender 类来用来管理 OpenGL 的渲染。
//接口 class VideoRender { public: virtual ~VideoRender(){} virtual void Init(int videoWidth, int videoHeight, int *dstSize) = 0; virtual void RenderVideoFrame(NativeImage *pImage) = 0; virtual void UnInit() = 0; }; //OpenGLRender 类定义 class OpenGLRender: public VideoRender{ public: virtual void Init(int videoWidth, int videoHeight, int *dstSize); virtual void RenderVideoFrame(NativeImage *pImage); virtual void UnInit(); //对应 Java 层 GLSurfaceView.Renderer 的三个接口 void OnSurfaceCreated(); void OnSurfaceChanged(int w, int h); void OnDrawFrame(); //静态实例管理 static OpenGLRender *GetInstance(); static void ReleaseInstance(); //设置变换矩阵,控制图像的旋转缩放 void UpdateMVPMatrix(int angleX, int angleY, float scaleX, float scaleY); private: OpenGLRender(); virtual ~OpenGLRender(); static std::mutex m_Mutex; static OpenGLRender* s_Instance; GLuint m_ProgramObj = GL_NONE; GLuint m_TextureId; GLuint m_VaoId; GLuint m_VboIds[3]; NativeImage m_RenderImage; glm::mat4 m_MVPMatrix;//变换矩阵 };
OpenGLRender 类的完整实现。
#include "OpenGLRender.h" #include <GLUtils.h> #include <gtc/matrix_transform.hpp> OpenGLRender* OpenGLRender::s_Instance = nullptr; std::mutex OpenGLRender::m_Mutex; static char vShaderStr[] = "#version 300 es\n" "layout(location = 0) in vec4 a_position;\n" "layout(location = 1) in vec2 a_texCoord;\n" "uniform mat4 u_MVPMatrix;\n" "out vec2 v_texCoord;\n" "void main()\n" "{\n" " gl_Position = u_MVPMatrix * a_position;\n" " v_texCoord = a_texCoord;\n" "}"; static char fShaderStr[] = "#version 300 es\n" "precision highp float;\n" "in vec2 v_texCoord;\n" "layout(location = 0) out vec4 outColor;\n" "uniform sampler2D s_TextureMap;//采样器\n" "void main()\n" "{\n" " outColor = texture(s_TextureMap, v_texCoord);\n" "}"; GLfloat verticesCoords[] = { -1.0f, 1.0f, 0.0f, // Position 0 -1.0f, -1.0f, 0.0f, // Position 1 1.0f, -1.0f, 0.0f, // Position 2 1.0f, 1.0f, 0.0f, // Position 3 }; GLfloat textureCoords[] = { 0.0f, 0.0f, // TexCoord 0 0.0f, 1.0f, // TexCoord 1 1.0f, 1.0f, // TexCoord 2 1.0f, 0.0f // TexCoord 3 }; GLushort indices[] = { 0, 1, 2, 0, 2, 3 }; OpenGLRender::OpenGLRender() { } OpenGLRender::~OpenGLRender() { // 释放缓存图像 NativeImageUtil::FreeNativeImage(&m_RenderImage); } //初始化视频图像的宽和高 void OpenGLRender::Init(int videoWidth, int videoHeight, int *dstSize) { LOGCATE("OpenGLRender::InitRender video[w, h]=[%d, %d]", videoWidth, videoHeight); std::unique_lock<std::mutex> lock(m_Mutex); m_RenderImage.format = IMAGE_FORMAT_RGBA; m_RenderImage.width = videoWidth; m_RenderImage.height = videoHeight; dstSize[0] = videoWidth; dstSize[1] = videoHeight; m_FrameIndex = 0; } // 接收解码后的视频帧 void OpenGLRender::RenderVideoFrame(NativeImage *pImage) { LOGCATE("OpenGLRender::RenderVideoFrame pImage=%p", pImage); if(pImage == nullptr || pImage->ppPlane[0] == nullptr) return; //加互斥锁,解码线程和渲染线程是 2 个不同的线程,避免数据访问冲突 std::unique_lock<std::mutex> lock(m_Mutex); if(m_RenderImage.ppPlane[0] == nullptr) { NativeImageUtil::AllocNativeImage(&m_RenderImage); } NativeImageUtil::CopyNativeImage(pImage, &m_RenderImage); } void OpenGLRender::UnInit() { } // 设置变换矩阵,控制图像的旋转缩放 void OpenGLRender::UpdateMVPMatrix(int angleX, int angleY, float scaleX, float scaleY) { angleX = angleX % 360; angleY = angleY % 360; //转化为弧度角 float radiansX = static_cast<float>(MATH_PI / 180.0f * angleX); float radiansY = static_cast<float>(MATH_PI / 180.0f * angleY); // Projection matrix glm::mat4 Projection = glm::ortho(-1.0f, 1.0f, -1.0f, 1.0f, 0.1f, 100.0f); //glm::mat4 Projection = glm::frustum(-ratio, ratio, -1.0f, 1.0f, 4.0f, 100.0f); //glm::mat4 Projection = glm::perspective(45.0f,ratio, 0.1f,100.f); // View matrix glm::mat4 View = glm::lookAt( glm::vec3(0, 0, 4), // Camera is at (0,0,1), in World Space glm::vec3(0, 0, 0), // and looks at the origin glm::vec3(0, 1, 0) // Head is up (set to 0,-1,0 to look upside-down) ); // Model matrix glm::mat4 Model = glm::mat4(1.0f); Model = glm::scale(Model, glm::vec3(scaleX, scaleY, 1.0f)); Model = glm::rotate(Model, radiansX, glm::vec3(1.0f, 0.0f, 0.0f)); Model = glm::rotate(Model, radiansY, glm::vec3(0.0f, 1.0f, 0.0f)); Model = glm::translate(Model, glm::vec3(0.0f, 0.0f, 0.0f)); m_MVPMatrix = Projection * View * Model; } void OpenGLRender::OnSurfaceCreated() { LOGCATE("OpenGLRender::OnSurfaceCreated"); m_ProgramObj = GLUtils::CreateProgram(vShaderStr, fShaderStr); if (!m_ProgramObj) { LOGCATE("OpenGLRender::OnSurfaceCreated create program fail"); return; } glGenTextures(1, &m_TextureId); glBindTexture(GL_TEXTURE_2D, m_TextureId); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glBindTexture(GL_TEXTURE_2D, GL_NONE); // Generate VBO Ids and load the VBOs with data glGenBuffers(3, m_VboIds); glBindBuffer(GL_ARRAY_BUFFER, m_VboIds[0]); glBufferData(GL_ARRAY_BUFFER, sizeof(verticesCoords), verticesCoords, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, m_VboIds[1]); glBufferData(GL_ARRAY_BUFFER, sizeof(textureCoords), textureCoords, GL_STATIC_DRAW); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_VboIds[2]); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW); // Generate VAO Id glGenVertexArrays(1, &m_VaoId); glBindVertexArray(m_VaoId); glBindBuffer(GL_ARRAY_BUFFER, m_VboIds[0]); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (const void *)0); glBindBuffer(GL_ARRAY_BUFFER, GL_NONE); glBindBuffer(GL_ARRAY_BUFFER, m_VboIds[1]); glEnableVertexAttribArray(1); glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(GLfloat), (const void *)0); glBindBuffer(GL_ARRAY_BUFFER, GL_NONE); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_VboIds[2]); glBindVertexArray(GL_NONE); UpdateMVPMatrix(0, 0, 1.0f, 1.0f); } void OpenGLRender::OnSurfaceChanged(int w, int h) { LOGCATE("OpenGLRender::OnSurfaceChanged [w, h]=[%d, %d]", w, h); m_ScreenSize.x = w; m_ScreenSize.y = h; glViewport(0, 0, w, h); glClearColor(1.0f, 1.0f, 1.0f, 1.0f); } void OpenGLRender::OnDrawFrame() { glClear(GL_COLOR_BUFFER_BIT); if(m_ProgramObj == GL_NONE || m_TextureId == GL_NONE || m_RenderImage.ppPlane[0] == nullptr) return; LOGCATE("OpenGLRender::OnDrawFrame [w, h]=[%d, %d]", m_RenderImage.width, m_RenderImage.height); m_FrameIndex++; //upload RGBA image data glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, m_TextureId); //加互斥锁,解码线程和渲染线程是 2 个不同的线程,避免数据访问冲突 std::unique_lock<std::mutex> lock(m_Mutex); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_RenderImage.width, m_RenderImage.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, m_RenderImage.ppPlane[0]); lock.unlock(); glBindTexture(GL_TEXTURE_2D, GL_NONE); // Use the program object glUseProgram (m_ProgramObj); glBindVertexArray(m_VaoId); GLUtils::setMat4(m_ProgramObj, "u_MVPMatrix", m_MVPMatrix); // Bind the RGBA map glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, m_TextureId); GLUtils::setFloat(m_ProgramObj, "s_TextureMap", 0); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0); } // 单例模式,全局只有一个 OpenGLRender OpenGLRender *OpenGLRender::GetInstance() { if(s_Instance == nullptr) { std::lock_guard<std::mutex> lock(m_Mutex); if(s_Instance == nullptr) { s_Instance = new OpenGLRender(); } } return s_Instance; } // 释放静态实例 void OpenGLRender::ReleaseInstance() { if(s_Instance != nullptr) { std::lock_guard<std::mutex> lock(m_Mutex); if(s_Instance != nullptr) { delete s_Instance; s_Instance = nullptr; } } }
OpenGLRender 在 JNI 层的调用。
JNIEXPORT void JNICALL Java_com_byteflow_learnffmpeg_media_FFMediaPlayer_native_1OnSurfaceCreated(JNIEnv *env, jclass clazz) { OpenGLRender::GetInstance()->OnSurfaceCreated(); } JNIEXPORT void JNICALL Java_com_byteflow_learnffmpeg_media_FFMediaPlayer_native_1OnSurfaceChanged(JNIEnv *env, jclass clazz, jint width, jint height) { OpenGLRender::GetInstance()->OnSurfaceChanged(width, height); } JNIEXPORT void JNICALL Java_com_byteflow_learnffmpeg_media_FFMediaPlayer_native_1OnDrawFrame(JNIEnv *env, jclass clazz) { OpenGLRender::GetInstance()->OnDrawFrame(); }
这里又回到了 OpenGL ES 开发领域,对这一块感兴趣的同学可以参考这篇Android OpenGL ES 从入门到精通系统性学习教程。
利用 OpenGL 实现好视频的渲染之后,可以很方便地利用 shader 添加你想要的视频滤镜,这里我们直接可以参考相机滤镜的实现。
我们将输出视频帧的一半渲染成经典黑白风格的图像,实现的 shader 如下:
//黑白滤镜 #version 300 es precision highp float; in vec2 v_texCoord; layout(location = 0) out vec4 outColor; uniform sampler2D s_TextureMap;//采样器 void main() { outColor = texture(s_TextureMap, v_texCoord); if(v_texCoord.x > 0.5) //将输出视频帧的一半渲染成经典黑白风格的图像 outColor = vec4(vec3(outColor.r*0.299 + outColor.g*0.587 + outColor.b*0.114), outColor.a); }
黑白滤镜的呈现效果:
动态网格滤镜是将视频图像分成规则的网格,动态修改网格的边框宽度,实现的 shader 如下:
//dynimic mesh 动态网格 #version 300 es precision highp float; in vec2 v_texCoord; layout(location = 0) out vec4 outColor; uniform sampler2D s_TextureMap;//采样器 uniform float u_Offset; uniform vec2 u_TexSize; void main() { vec2 imgTexCoord = v_texCoord * u_TexSize; float sideLength = u_TexSize.y / 6.0; float maxOffset = 0.15 * sideLength; float x = mod(imgTexCoord.x, floor(sideLength)); float y = mod(imgTexCoord.y, floor(sideLength)); float offset = u_Offset * maxOffset; if(offset <= x && x <= sideLength - offset && offset <= y && y <= sideLength - offset) { outColor = texture(s_TextureMap, v_texCoord); } else { outColor = vec4(1.0, 1.0, 1.0, 1.0); } }
动态网格滤镜的渲染过程:
glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, m_TextureId); std::unique_lock<std::mutex> lock(m_Mutex); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_RenderImage.width, m_RenderImage.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, m_RenderImage.ppPlane[0]); lock.unlock(); glBindTexture(GL_TEXTURE_2D, GL_NONE); //指定着色器程序 glUseProgram (m_ProgramObj); //绑定 VAO glBindVertexArray(m_VaoId); //传入变换矩阵 GLUtils::setMat4(m_ProgramObj, "u_MVPMatrix", m_MVPMatrix); //绑定纹理 glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, m_TextureId); GLUtils::setFloat(m_ProgramObj, "s_TextureMap", 0); //设置偏移量 float offset = (sin(m_FrameIndex * MATH_PI / 25) + 1.0f) / 2.0f; GLUtils::setFloat(m_ProgramObj, "u_Offset", offset); //设置图像尺寸 GLUtils::setVec2(m_ProgramObj, "u_TexSize", vec2(m_RenderImage.width, m_RenderImage.height)); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, (const void *)0);
动态网格滤镜的呈现效果:
我们在 GLSurfaceView 监听用户的滑动和缩放手势,控制 OpenGLRender 的变换矩阵,从而实现视频图像的旋转和缩放。
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