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我尝试使用 FFmpeg 来捕获 OpenGL 渲染的帧。结果是一个用于播放的 .mp4 文件。它可以工作,因为我得到了我期望的 .mp4,但是与 OpenGL 渲染的质量相比,质量相当低。谁能告诉我为什么?以及如何调整我的代码以使 mp4 与 OpenGL 生成的原始帧质量相同?
我得到的结果:
图像 OpenGL 与 FFmpeg
这是我的简单代码:
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include <iostream>
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
// settings
const unsigned int SCR_WIDTH = 500;
const unsigned int SCR_HEIGHT = 500;
// start ffmpeg telling it to expect raw rgba 720p-60hz frames
// -i - tells it to read frames from stdin
const char* cmd = "ffmpeg -f rawvideo -pix_fmt rgba -s 500x500 -i - "
"-threads 0 -preset fast -y -pix_fmt yuv420p -crf 21 -vf vflip output.mp4";
// open pipe to ffmpeg's stdin in binary write mode
FILE* ffmpeg = _popen(cmd, "wb");
int* buffer = new int[SCR_WIDTH*SCR_HEIGHT];
// shaders
const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec3 aColor;\n"
"layout (location = 2) in vec2 aTexCoord;\n"
"out vec3 ourColor;\n"
"out vec2 texCoord;\n"
"uniform mat4 transform;\n"
"void main()\n"
"{\n"
" gl_Position = transform*vec4(aPos, 1.0);\n"
" ourColor = aColor;\n"
" texCoord = aTexCoord;\n"
"}\0";
const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"in vec3 ourColor;\n"
"in vec2 texCoord;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.0f, 0.0f, 1.0f);\n"
"}\n\0";
int main()
{
// glfw: initialize and configure
// ------------------------------
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
// glfw window creation
// --------------------
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
// glad: load all OpenGL function pointers
// ---------------------------------------
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// render preparation: data collection and passing
// -----------------------------------------------
// vertex shader: create and compile
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// fragment shader: create and compile
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// shader program
unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
// first shape: square
float vertices[] = {
// positions // colors // texture coords
0.25f, 0.25f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.25f, -0.25f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.25f, -0.25f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // bottom left
-0.25f, 0.25f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left
};
int indices[] = {
0, 1, 2,
2, 3, 0
};
unsigned int VAO, VBO, EBO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glGenBuffers(1, &EBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), 0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), 0);
glEnableVertexAttribArray(1);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), 0);
glEnableVertexAttribArray(2);
// second shape: line(from the center of the screen to the center of the square
float vertices2[] = {
0.0f, 0.0f, 0.0f,
0.5f, 0.5f, 0.0f
};
unsigned int VAO2, VBO2;
glGenVertexArrays(1, &VAO2);
glGenBuffers(1, &VBO2);
glBindVertexArray(VAO2);
glBindBuffer(GL_ARRAY_BUFFER, VBO2);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0);
glEnableVertexAttribArray(0);
// wireframe mode
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
int frameCounter = 0;
// render loop
// -----------
while (!glfwWindowShouldClose(window))
{
if (frameCounter > 900) break;
// input
// -----
processInput(window);
// render
// ------
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// be sure to activate the shader before any calls to glUniform
glUseProgram(shaderProgram);
/**********************draw rotating line*****************************/
glm::mat4 transform = glm::mat4(1.0f);
/// rotate( around the center of the screen )
transform = glm::rotate(transform, (float)glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));
unsigned int transLoc = glGetUniformLocation(shaderProgram, "transform");
glUniformMatrix4fv(transLoc, 1, GL_FALSE, glm::value_ptr(transform));
// draw
glBindVertexArray(VAO2);
glDrawArrays(GL_LINES, 0, 2);
/**********************draw rotating square*****************************/
transform = glm::mat4(1.0f);
/// rotate( around the center of the screen )
transform = glm::rotate(transform, (float)glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));
//// translate
transform = glm::translate(transform, glm::vec3(0.5f, 0.5f, 0.0f));
//// rotate( self rotate)
transform = glm::rotate(transform, (float)glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));
transLoc = glGetUniformLocation(shaderProgram, "transform");
glUniformMatrix4fv(transLoc, 1, GL_FALSE, glm::value_ptr(transform));
// draw
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
/**********************draw center squares*****************************/
transform = glm::mat4(1.0f);
float scaler = sin((float)glfwGetTime())*4;
transform = glm::scale(transform, glm::vec3(scaler, scaler, scaler));
transLoc = glGetUniformLocation(shaderProgram, "transform");
glUniformMatrix4fv(transLoc, 1, GL_FALSE, glm::value_ptr(transform));
// draw
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
// -------------------------------------------------------------------------------
glfwSwapBuffers(window);
/****** ffmpeg *****/
glReadPixels(0, 0, SCR_WIDTH, SCR_HEIGHT, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
fwrite(buffer, sizeof(int)*SCR_WIDTH*SCR_HEIGHT, 1, ffmpeg);
frameCounter++;
/****** end: ffmpeg *****/
glfwPollEvents();
}
_pclose(ffmpeg);
// glfw: terminate, clearing all previously allocated GLFW resources.
// ------------------------------------------------------------------
glfwTerminate();
return 0;
}
// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
// make sure the viewport matches the new window dimensions; note that width and
// height will be significantly larger than specified on retina displays.
glViewport(0, 0, width, height);
}
最佳答案
切换到libx264rgb
编码器 & crf 0
对于无损捕获:
const char* cmd = "ffmpeg -framerate 60 -f rawvideo -pix_fmt rgba -s 500x500 -i - "
"-c:v libx264rgb -threads 0 -preset fast -y -crf 0 -vf vflip output.mp4";
请注意,在将输出传递给其他比
ffmpeg
更通用的软件之前,您需要重新编码输出。因为 RGB 不是 H.264 非常常见的色彩空间。
--profile=gpu-hq
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