/*
Copyright (C) 2005 Nick Lowe (nickl@vislab.usyd.edu.au)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.
ABOUT
------
This "library" can be used with some GLX programs to record frames
to disk. It makes a couple of assumptions:
- The program only uses one GL context
- The program uses double-buffering and calls glXSwapBuffers()
only at the end of each frame
- The window does not get resized during program executation
It outputs .jpg files to the current working directory. This can be
easily changed by modifying the code (not elegant I know).
Even with these assumptions, this "library" should cover a lot of
GLX and GLUT programs. I've tested Tux Racer, many GL screensavers,
and a few of my own programs (that use GLUT).
DEPENDENCIES
------------
Aside from common dependencies, this file requires OpenIL
(aka. DevIL) to save images (install "libdevil-dev" under Ubuntu).
USAGE
-----
Compile using:
gcc -Wall -O2 -fpic -shared -ldl -lIL -o libglxdump.so glxdump.c
or for DEBUG (more output):
gcc -Wall -O2 -fpic -shared -ldl -lIL -DDEBUG -o libglxdump.so glxdump.c
Run using:
LD_PRELOAD=`pwd`/libglxdump.so [some glx application]
Encode using:
mogrify -resize [width]x[height]! *.jpg
ffmpeg -s [width]x[height] -i image_%10d.jpg video.avi
(NOTES: mogrify is *very* slow; ffmpeg has many options for better quality)
REFERENCES
----------
http://www.linuxjournal.com/article/7795
http://www.amparo.net/ce155/fork-ex.html
http://www.opengroup.org/onlinepubs/009695399/functions/exec.html
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>
#include <math.h>
#include <dlfcn.h>
#include <GL/glx.h>
#include <IL/il.h>
#define VIDEO_TIME_STEP 40.0 /* milliseconds between frames (40.0 = 25 fps) */
/* library interception variables */
static void* lib_handle = 0;
static void (*lib_glXSwapBuffers)(Display *dpy, GLXDrawable drawable) = 0;
/* timing variables */
static double video_time;
/* image saving variables */
static GLint viewport[4];
static ILuint image_id = 0;
static GLubyte* image_data = 0;
static int image_number = 0;
/*
* Output error code and exit
*/
inline static void handle_dlerror(void)
{
char* error;
error = dlerror();
if (error)
{
fprintf(stderr, "%s\n", error);
exit(1);
}
}
/*
* Load GLX library and find glXSwapBuffers() function
*/
inline static void load_library(void)
{
/* open library (NOTE: you may need to change this filename!) */
lib_handle = dlopen("/usr/lib/libGL.so", RTLD_LAZY);
if (!lib_handle)
handle_dlerror();
/* intercept library glxSwapBuffers function */
lib_glXSwapBuffers = dlsym(lib_handle, "glXSwapBuffers");
handle_dlerror();
}
/*
* Create an image to store each frame in (using OpenIL)
*/
inline static void create_image(void)
{
int width;
int height;
glGetIntegerv(GL_VIEWPORT, viewport);
width = viewport[2] - viewport[0];
height = viewport[3] - viewport[1];
//width = 1680;
//height = 1050;
printf("Capturing at %dx%d\n", width, height);
ilInit();
ilGenImages(1, &image_id);
ilBindImage(image_id);
image_data = (GLubyte*)malloc(width * height * 4 * sizeof(GLubyte));
ilTexImage(width, height, 1, 4, GL_RGBA, GL_UNSIGNED_BYTE, image_data);
#ifdef DEBUG
printf("Created image using viewport (%d, %d, %d, %d)\n",
viewport[0], viewport[1], viewport[2], viewport[3]);
#endif
}
/*
* Read-back a frame from the GL framebuffer
*/
inline static void capture_frame(void)
{
glReadPixels(viewport[0], viewport[1], viewport[2], viewport[3],
GL_RGBA, GL_UNSIGNED_BYTE, image_data);
#ifdef DEBUG
printf("Captured frame\n");
#endif
}
static char filename[32];
inline static void set_filename(void)
{
sprintf(filename, "image_%.10u.jpg" , image_number);
}
/*
* Dump the current frame to disk
*/
inline static void dump_frame(void)
{
/* save image (NOTE: you can change to a different file format!) */
ilSetData(image_data);
ilSave(IL_JPG, filename);
#ifdef DEBUG
printf("Dumped frame to %s\n", filename);
#endif
}
/*
* Record time that capturing starts
*/
inline static void start_timer(void)
{
struct timeval tp;
gettimeofday(&tp, 0);
video_time = 1000.0 * tp.tv_sec + 0.001 * tp.tv_usec;
}
/*
* Dump frames at the correct rate (NOTE: will write duplicates or drop frames!)
*/
inline static void dump_frames()
{
struct timeval tp;
double t;
gettimeofday(&tp, 0);
t = 1000.0 * tp.tv_sec + 0.001 * tp.tv_usec;
/* only capture if we will be dumping any frames */
if ((t - video_time) > VIDEO_TIME_STEP)
{
capture_frame();
set_filename();
dump_frame();
image_number++;
video_time += VIDEO_TIME_STEP;
}
while ((t - video_time) > VIDEO_TIME_STEP)
{
static char old_filename[32];
int pid;
/* record current frame filename */
strcpy(old_filename, filename);
/* fork a child process to copy frames (to fill in timestep) */
if ((pid = fork()) < 0)
{
perror("Problem calling vfork");
exit(1);
}
/* child copies frames and exits */
if (pid == 0)
{
set_filename();
if (execlp("cp", "cp", old_filename, filename, (char*)0) == -1)
{
perror("Error copying frame");
exit(1);
}
#ifdef DEBUG
printf("Copied frame from %s to %s\n", old_filename, filename);
#endif
exit(0);
}
wait();
image_number++;
video_time += VIDEO_TIME_STEP;
}
}
/*
* Our glXSwapBuffers function that intercepts the "real" function.
*
* Load library if necessary. Then dump a frame and call the "real"
* glXSwapBuffers function.
*/
void glXSwapBuffers(Display *dpy, GLXDrawable drawable)
{
if (!lib_handle)
{
load_library();
create_image();
start_timer();
}
dump_frames();
lib_glXSwapBuffers(dpy, drawable);
#ifdef DEBUG
printf("Intercepted call to glXSwapBuffers()\n");
#endif
}