[vlc-devel] [PATCH 3/4] libvlc: add sdl_opengl_player sample

Pierre Lamot pierre at videolabs.io
Tue Jul 3 14:38:36 CEST 2018


  this sample shows a simple use of libvlc_video_set_opengl_callbacks
---
 doc/libvlc/sdl_opengl_player.cpp | 316 +++++++++++++++++++++++++++++++
 1 file changed, 316 insertions(+)
 create mode 100644 doc/libvlc/sdl_opengl_player.cpp

diff --git a/doc/libvlc/sdl_opengl_player.cpp b/doc/libvlc/sdl_opengl_player.cpp
new file mode 100644
index 0000000000..290b680629
--- /dev/null
+++ b/doc/libvlc/sdl_opengl_player.cpp
@@ -0,0 +1,316 @@
+//g++ sdl_opengl_player.cpp $(pkg-config --cflags --libs libvlc sdl2 gl)
+
+/* Licence WTFPL  */
+/* Written by Pierre Lamot */
+
+#include <exception>
+#include <mutex>
+#include <iostream>
+
+#include <SDL2/SDL.h>
+#define GL_GLEXT_PROTOTYPES 1
+#include <SDL2/SDL_opengl.h>
+#include <vlc/vlc.h>
+
+/*
+ * This program show how to use libvlc_video_set_opengl_callbacks API.
+ *
+ * The main idea is to set up libvlc to render into FBO, and to use a
+ * triple buffer mechanism to share textures between VLC and the rendering
+ * thread of our application
+ */
+
+// Shader sources
+const GLchar* vertexSource =
+    "attribute vec4 a_position;    \n"
+    "attribute vec2 a_uv;          \n"
+    "varying vec2 v_TexCoordinate; \n"
+    "void main()                   \n"
+    "{                             \n"
+    "    v_TexCoordinate = a_uv;   \n"
+    "    gl_Position = vec4(a_position.xyz, 1.0);  \n"
+    "}                             \n";
+
+const GLchar* fragmentSource =
+    "precision mediump float;      \n"
+    "uniform sampler2D u_videotex;   \n"
+    "varying vec2 v_TexCoordinate; \n"
+    "void main()                   \n"
+    "{                             \n"
+    "    gl_FragColor = texture2D(u_videotex, v_TexCoordinate); \n"
+    "}                             \n";
+
+class VLCVideo
+{
+public:
+    VLCVideo(SDL_Window *window):
+        m_win(window)
+    {
+        const char *args[] = {
+            "--verbose=4"
+        };
+        m_vlc = libvlc_new(sizeof(args) / sizeof(*args), args);
+
+        //VLC opengl context needs to be shared with SDL context
+        SDL_GL_SetAttribute(SDL_GL_SHARE_WITH_CURRENT_CONTEXT, 1);
+        m_ctx = SDL_GL_CreateContext(window);
+    }
+
+    ~VLCVideo()
+    {
+        stop();
+        if (m_vlc)
+            libvlc_release(m_vlc);
+    }
+
+    bool playMedia(const char* url)
+    {
+        m_media = libvlc_media_new_location (m_vlc, url);
+        if (m_media == NULL) {
+            fprintf(stderr, "unable to create media %s", url);
+            return false;
+        }
+        m_mp = libvlc_media_player_new_from_media (m_media);
+        if (m_mp == NULL) {
+            fprintf(stderr, "unable to create media player");
+            libvlc_media_release(m_media);
+            return false;
+        }
+        // Define the opengl rendering callbacks
+        libvlc_video_set_opengl_callbacks(m_mp, create_fbo, destroy_fbo, make_current, get_proc_address, render_fbo, this);
+
+        // Play the video
+        libvlc_media_player_play (m_mp);
+
+        return true;
+    }
+
+    void stop()
+    {
+        if (m_mp) {
+            libvlc_media_player_release(m_mp);
+            m_mp = nullptr;
+        }
+        if (m_media) {
+            libvlc_media_release(m_media);
+            m_media = nullptr;
+        }
+    }
+
+    /// return the texture to be displayed
+    GLuint getVideoFrame(bool* out_updated)
+    {
+        std::lock_guard<std::mutex> lock(m_text_lock);
+        if (out_updated)
+            *out_updated = m_updated;
+        if (m_updated) {
+            std::swap(m_idx_swap, m_idx_display);
+            m_updated = false;
+        }
+        return m_tex[m_idx_display];
+    }
+
+    /// this callback is called to create the surfaces and FBO used by VLC to perform its rendering
+    static void create_fbo(void* data, size_t width, size_t height)
+    {
+        VLCVideo* that = reinterpret_cast<VLCVideo*>(data);
+        glGenTextures(3, that->m_tex);
+        glGenFramebuffers(3, that->m_fbo);
+
+        for (int i = 0; i < 3; i++) {
+            glBindTexture(GL_TEXTURE_2D, that->m_tex[i]);
+            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+            glTexParameteri(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);
+
+            glBindFramebuffer(GL_FRAMEBUFFER, that->m_fbo[i]);
+            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, that->m_tex[i], 0);
+        }
+        glBindTexture(GL_TEXTURE_2D, 0);
+
+        GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+
+        if (status != GL_FRAMEBUFFER_COMPLETE) {
+            return;
+        }
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+
+    // This callback is called to release resources created by create_fbo
+    static void destroy_fbo(void* data)
+    {
+        VLCVideo* that = reinterpret_cast<VLCVideo*>(data);
+        glDeleteTextures(3, that->m_tex);
+        glDeleteFramebuffers(3, that->m_fbo);
+    }
+
+    //This callback is called before and after VLC render the videoframe
+    //This will bind the rendering FBO to the current context
+    static void render_fbo(void* data, bool enter)
+    {
+        VLCVideo* that = reinterpret_cast<VLCVideo*>(data);
+        if (enter) {
+            glBindFramebuffer(GL_FRAMEBUFFER, that->m_fbo[that->m_idx_render]);
+        } else {
+            glBindFramebuffer(GL_FRAMEBUFFER, 0);
+            {
+                std::lock_guard<std::mutex> lock(that->m_text_lock);
+                that->m_updated = true;
+                std::swap(that->m_idx_swap, that->m_idx_render);
+            }
+        }
+    }
+
+    // This callback is called to set the OpenGL context
+    static bool make_current(void* data, bool current)
+    {
+        VLCVideo* that = reinterpret_cast<VLCVideo*>(data);
+        if (current)
+            return SDL_GL_MakeCurrent(that->m_win, that->m_ctx) == 0;
+        else
+            return SDL_GL_MakeCurrent(that->m_win, 0) == 0;
+    }
+
+    // This callback is called by VLC to get OpenGL functions.
+    static void* get_proc_address(void* /*data*/, const char* current)
+    {
+        return SDL_GL_GetProcAddress(current);
+    }
+
+private:
+    //VLC objects
+    libvlc_instance_t*  m_vlc = nullptr;
+    libvlc_media_player_t* m_mp = nullptr;
+    libvlc_media_t* m_media = nullptr;
+
+    //FBO data
+    std::mutex m_text_lock;
+    GLuint m_tex[3];
+    GLuint m_fbo[3];
+    size_t m_idx_render = 0;
+    size_t m_idx_swap = 1;
+    size_t m_idx_display = 2;
+    bool m_updated = false;
+
+    //SDL context
+    SDL_Window* m_win;
+    SDL_GLContext m_ctx;
+};
+
+int main(int argc, char** argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "usage: %s <uri>\n", argv[0]);
+        return 1;
+    }
+
+    // SDL_Init(SDL_INIT_VIDEO);
+    SDL_Window* wnd = SDL_CreateWindow("test",
+        SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
+        640, 480, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
+
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
+    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
+    SDL_GL_SetSwapInterval(0);
+    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
+    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
+
+    SDL_GLContext glc = SDL_GL_CreateContext(wnd);
+
+    VLCVideo video(wnd);
+
+    SDL_Renderer* rdr = SDL_CreateRenderer(
+        wnd, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);
+
+    // Create Vertex Array Object
+    GLuint vao;
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+
+    // Create a Vertex Buffer Object and copy the vertex data to it
+    GLuint vbo;
+    glGenBuffers(1, &vbo);
+
+    //vertex X, vertex Y, UV X, UV Y
+    GLfloat vertices[] = {
+        -0.5f,  0.5f, 0.f, 1.f,
+        -0.5f, -0.5f, 0.f, 0.f,
+         0.5f,  0.5f, 1.f, 1.f,
+         0.5f, -0.5f, 1.f, 0.f
+    };
+
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+
+    // Create and compile the vertex shader
+    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
+    glShaderSource(vertexShader, 1, &vertexSource, NULL);
+    glCompileShader(vertexShader);
+
+    // Create and compile the fragment shader
+    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
+    glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
+    glCompileShader(fragmentShader);
+
+    // Link the vertex and fragment shader into a shader program
+    GLuint shaderProgram = glCreateProgram();
+    glAttachShader(shaderProgram, vertexShader);
+    glAttachShader(shaderProgram, fragmentShader);
+    glLinkProgram(shaderProgram);
+    glUseProgram(shaderProgram);
+
+    // Specify the layout of the vertex data
+    GLint posAttrib = glGetAttribLocation(shaderProgram, "a_position");
+    glEnableVertexAttribArray(posAttrib);
+    glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 4*sizeof(float), 0);
+
+    // Specify the layout of the vertex data
+    GLint uvAttrib = glGetAttribLocation(shaderProgram, "a_uv");
+    glEnableVertexAttribArray(uvAttrib);
+    glVertexAttribPointer(uvAttrib, 2, GL_FLOAT, GL_FALSE, 4*sizeof(float), (GLvoid*)(2*sizeof(float)));
+
+    // Specify the texture of the video
+    GLint textUniform = glGetUniformLocation(shaderProgram, "u_videotex");
+    glActiveTexture(GL_TEXTURE0);
+    glUniform1i(textUniform, /*GL_TEXTURE*/0);
+
+    //start playing the video
+    if (!video.playMedia(argv[1])) {
+        SDL_DestroyWindow(wnd);
+        SDL_Quit();
+        return 1;
+    }
+
+    bool updated = false;
+    bool quit = false;
+    while(!quit) {
+        SDL_Event e;
+        while(SDL_PollEvent(&e)) {
+            if(e.type == SDL_QUIT)
+                quit = true;
+        }
+
+        // Clear the screen to black
+        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+
+        // Get the current video texture and bind it
+        GLuint tex = video.getVideoFrame(&updated);
+        glBindTexture(GL_TEXTURE_2D, tex);
+
+        // Draw the video rectangle
+        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+        glBindTexture(GL_TEXTURE_2D, 0);
+
+        SDL_GL_SwapWindow(wnd);
+    };
+
+    video.stop();
+
+    SDL_DestroyWindow(wnd);
+    SDL_Quit();
+
+    return 0;
+}
-- 
2.17.1



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