纯cpu环境集成gltransition

gltransition

gl-transitions 使用glsl定义了转场框架, 使用者在框架内实现转场算法/效果.

它的展示站点https://gl-transitions.com/使用webgl展示了这些转场效果.

一个简单的fade效果实现如下:

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// transition of a simple fade.
vec4 transition (vec2 uv) {
  return mix(
    getFromColor(uv),
    getToColor(uv),
    progress
  );
}

转场效果只用实现glsl函数vec4 transition (vec2 uv), 输入是vec2像素坐标，输出是vec4像素. 算法可以使用的上下文包括progress,转场进度等参数.

ffmpeg集成

ffmpeg-gl-transition项目将gl-transitions转场框架作为一个filter集成到了ffmpeg中，集成后可以通过ffmpeg filter使用到gl-transitions内众多的转场效果处理视频转场.

纯CPU渲染

如果是在linux服务端，headless且无GPU的情况下，想要使用ffmpeg-gl-transition, 那么可以依赖于software opengl环境.

有两种方式，一种是使用xvfb，这是一个虚拟的X server, 它内置了cpu模拟的opengl渲染环境, 但是运行时需要套上一层xvfb-run.

第二种方式是直接使用osmesa, osmesa是linux下实现的一套software opengl, 后端渲染引擎是llvm-pipe, 使用多线程方式模拟GPU管线计算. 实际上xvfb内部也使用了这一套软件OPENGL实现.

要支持纯osmesa渲染，只要将ffmpeg-gl-transition项目实现的vf_gltransition.c改动一下即可，将OPENGL环境的初始化

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--- vf_gltransition.c		2019-08-31 18:16:04.424219700 +0800
+++ vf_gltransitionosmesa.c	2022-08-31 12:54:50.119997700 +0800
@@ -8,24 +8,7 @@
 #include "internal.h"
 #include "framesync.h"
 
-#ifndef __APPLE__
-# define GL_TRANSITION_USING_EGL //remove this line if you don't want to use EGL
-#endif
-
-#ifdef __APPLE__
-# define __gl_h_
-# define GL_DO_NOT_WARN_IF_MULTI_GL_VERSION_HEADERS_INCLUDED
-# include <OpenGL/gl3.h>
-#else
-# include <GL/glew.h>
-#endif
-
-#ifdef GL_TRANSITION_USING_EGL
-# include <EGL/egl.h>
-# include <EGL/eglext.h>
-#else
-# include <GLFW/glfw3.h>
-#endif
+#include "GL/osmesa.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -36,16 +19,6 @@
 
 #define PIXEL_FORMAT (GL_RGB)
 
-#ifdef GL_TRANSITION_USING_EGL
-static const EGLint configAttribs[] = {
-    EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
-    EGL_BLUE_SIZE, 8,
-    EGL_GREEN_SIZE, 8,
-    EGL_RED_SIZE, 8,
-    EGL_DEPTH_SIZE, 8,
-    EGL_RENDERABLE_TYPE, EGL_OPENGL_BIT,
-    EGL_NONE};
-#endif
 static const float position[12] = {
   -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f
 };
@@ -114,14 +87,10 @@
   // internal state
   GLuint        posBuf;
   GLuint        program;
-#ifdef GL_TRANSITION_USING_EGL
-  EGLDisplay eglDpy;
-  EGLConfig eglCfg;
-  EGLSurface eglSurf;
-  EGLContext eglCtx;
-#else
-  GLFWwindow    *window;
-#endif
+
+  //
+  OSMesaContext osmesa_ctx;
+  void* buffer;
 
   GLchar *f_shader_source;
 } GLTransitionContext;
@@ -130,7 +99,7 @@
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 
 static const AVOption gltransition_options[] = {
-  { "duration", "transition duration in seconds", OFFSET(duration), AV_OPT_TYPE_DOUBLE, {.dbl=1.0}, 0, DBL_MAX, FLAGS },
+  { "duration", "transition duration in seconds", OFFSET(duration), AV_OPT_TYPE_DOUBLE, {.dbl=3.0}, 0, DBL_MAX, FLAGS },
   { "offset", "delay before startingtransition in seconds", OFFSET(offset), AV_OPT_TYPE_DOUBLE, {.dbl=0.0}, 0, DBL_MAX, FLAGS },
   { "source", "path to the gl-transition source file (defaults to basic fade)", OFFSET(source), AV_OPT_TYPE_STRING, {.str = NULL}, CHAR_MIN, CHAR_MAX, FLAGS },
   {NULL}
@@ -269,7 +238,8 @@
   GLTransitionContext *c = ctx->priv;
 
   c->progress = glGetUniformLocation(c->program, "progress");
-  glUniform1f(c->progress, 0.0f);
+  float progress_init = 0.0;
+  glUniform1fv(c->progress, 1, &progress_init);
 
   // TODO: this should be output ratio
   c->ratio = glGetUniformLocation(c->program, "ratio");
@@ -289,63 +259,24 @@
   GLTransitionContext *c = ctx->priv;
 
 
-#ifdef GL_TRANSITION_USING_EGL
-  //init EGL
-  // 1. Initialize EGL
-  // c->eglDpy = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-
-  #define MAX_DEVICES 4
-  EGLDeviceEXT eglDevs[MAX_DEVICES];
-  EGLint numDevices;
-
-  PFNEGLQUERYDEVICESEXTPROC eglQueryDevicesEXT =(PFNEGLQUERYDEVICESEXTPROC)
-  eglGetProcAddress("eglQueryDevicesEXT");
-
-  eglQueryDevicesEXT(MAX_DEVICES, eglDevs, &numDevices);
-
-  PFNEGLGETPLATFORMDISPLAYEXTPROC eglGetPlatformDisplayEXT =  (PFNEGLGETPLATFORMDISPLAYEXTPROC)
-  eglGetProcAddress("eglGetPlatformDisplayEXT");
-
-  c->eglDpy = eglGetPlatformDisplayEXT(EGL_PLATFORM_DEVICE_EXT, eglDevs[0], 0);
-
-  EGLint major, minor;
-  eglInitialize(c->eglDpy, &major, &minor);
-  av_log(ctx, AV_LOG_DEBUG, "%d%d", major, minor);
-  // 2. Select an appropriate configuration
-  EGLint numConfigs;
-  EGLint pbufferAttribs[] = {
-      EGL_WIDTH,
-      inLink->w,
-      EGL_HEIGHT,
-      inLink->h,
-      EGL_NONE,
-  };
-  eglChooseConfig(c->eglDpy, configAttribs, &c->eglCfg, 1, &numConfigs);
-  // 3. Create a surface
-  c->eglSurf = eglCreatePbufferSurface(c->eglDpy, c->eglCfg,
-                                       pbufferAttribs);
-  // 4. Bind the API
-  eglBindAPI(EGL_OPENGL_API);
-  // 5. Create a context and make it current
-  c->eglCtx = eglCreateContext(c->eglDpy, c->eglCfg, EGL_NO_CONTEXT, NULL);
-  eglMakeCurrent(c->eglDpy, c->eglSurf, c->eglSurf, c->eglCtx);
-#else
-  //glfw
-
-  glfwWindowHint(GLFW_VISIBLE, 0);
-  c->window = glfwCreateWindow(inLink->w, inLink->h, "", NULL, NULL);
-  if (!c->window) {
-    av_log(ctx, AV_LOG_ERROR, "setup_gl ERROR");
-    return -1;
+
+  c->osmesa_ctx = OSMesaCreateContext(OSMESA_RGBA, NULL);
+
+  if (!c->osmesa_ctx) {
+      printf("OSMesaCreateContext failed!\n");
+      return 0;
   }
-  glfwMakeContextCurrent(c->window);
 
-#endif
+  c->buffer = malloc( inLink->w* inLink->h* 4 * sizeof(GLubyte) );
+  if (!c->buffer) {
+      printf("Alloc image buffer failed!\n");
+      return 0;
+  }
 
-#ifndef __APPLE__
-  glewExperimental = GL_TRUE;
-  glewInit();
-#endif
+  if (!OSMesaMakeCurrent(c->osmesa_ctx, c->buffer, GL_UNSIGNED_BYTE, inLink->w, inLink->h)) {
+      printf("OSMesaMakeCurrent failed!\n");
+      return 0;
+  }
 
   glViewport(0, 0, inLink->w, inLink->h);
 
@@ -380,18 +311,20 @@
 
   av_frame_copy_props(outFrame, fromFrame);
 
-#ifdef GL_TRANSITION_USING_EGL
-  eglMakeCurrent(c->eglDpy, c->eglSurf, c->eglSurf, c->eglCtx);
-#else
-  glfwMakeContextCurrent(c->window);
-#endif
+
+  if (!OSMesaMakeCurrent( c->osmesa_ctx, c->buffer, GL_UNSIGNED_BYTE, outLink->w, outLink->h)) {
+      printf("OSMesaMakeCurrent failed!\n");
+      return 0;
+  }
 
   glUseProgram(c->program);
 
   const float ts = ((fs->pts - c->first_pts) / (float)fs->time_base.den) - c->offset;
   const float progress = FFMAX(0.0f, FFMIN(1.0f, ts / c->duration));
-  // av_log(ctx, AV_LOG_ERROR, "transition '%s' %llu %f %f\n", c->source, fs->pts - c->first_pts, ts, progress);
-  glUniform1f(c->progress, progress);
+  //av_log(ctx, AV_LOG_ERROR, "transition '%s' %llu %f %f %d\n", c->source, fs->pts - c->first_pts, ts, progress, c->progress);
+  glUniform1fv(c->progress, 1, &progress);
+  float pp = -1.0;
+  glGetUniformfv(c->program, c->progress, &pp);
 
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 
@@ -454,12 +387,6 @@
   c->first_pts = AV_NOPTS_VALUE;
 
 
-#ifndef GL_TRANSITION_USING_EGL
-  if (!glfwInit())
-  {
-    return -1;
-  }
-#endif
 
   return 0;
 }
@@ -468,23 +395,13 @@
   GLTransitionContext *c = ctx->priv;
   ff_framesync_uninit(&c->fs);
 
-#ifdef GL_TRANSITION_USING_EGL
-  if (c->eglDpy) {
-    glDeleteTextures(1, &c->from);
-    glDeleteTextures(1, &c->to);
-    glDeleteBuffers(1, &c->posBuf);
-    glDeleteProgram(c->program);
-    eglTerminate(c->eglDpy);
-  }
-#else
-  if (c->window) {
-    glDeleteTextures(1, &c->from);
-    glDeleteTextures(1, &c->to);
-    glDeleteBuffers(1, &c->posBuf);
-    glDeleteProgram(c->program);
-    glfwDestroyWindow(c->window);
-  }
-#endif
+  glDeleteTextures(1, &c->from);
+  glDeleteTextures(1, &c->to);
+  glDeleteBuffers(1, &c->posBuf);
+  glDeleteProgram(c->program);
+
+  OSMesaDestroyContext(c->osmesa_ctx);
+  free(c->buffer);
 
   if (c->f_shader_source) {
     av_freep(&c->f_shader_source);

文章目录

gltransition

ffmpeg集成

纯CPU渲染