refactor: specify number of video input buffers

README.md

@@ -174,9 +174,9 @@ These are configurable in the [`forge_project.cfg`](#forge_projectcfg).
 ### CLI arguments
 
 ```txt
-forge steel-dev
+forge steel-VERSION
 
-usage: forge [-h] [-v] [-p=PROJECT_PATH] [-c=CFG_FILE] [-hr] [-s=SCREEN] [-m=SCREEN] [-mo] [-w] [-t=TEMPO] [-d] [-ar / -nar] [-arc=CYCLES] [-vi=FILE] [-vs=SIZE] [-vr / -nvr] [-is=SIZE] [-ls / -nls] [-ss / -nss] [-mr / -nmr] [-tm] [-tf]
+usage: forge [-h] [-v] [-p=PROJECT_PATH] [-c=CFG_FILE] [-hr] [-s=SCREEN] [-m=SCREEN] [-mo] [-w] [-t=TEMPO] [-d] [-ar / -nar] [-arc=CYCLES] [-vi=FILE] [-vs=SIZE] [-vb=COUNT] [-vr / -nvr] [-is=SIZE] [-ls / -nls] [-ss / -nss] [-mr / -nmr] [-tm] [-tf]
 
 Fusion Of Real-time Generative Effects.
 
@@ -196,6 +196,7 @@ options:
   -nar, --no-auto-random      do not randomize state (default)
   -arc, --auto-random-cycle   auto random cycle length (default: 4)
   -vi, --video-in             path to video capture device (multiple allowed)
+  -vb, --video-buffers        number of video buffers to use (default: 2)
   -vs, --video-size           video capture desired height (default: internal texture height)
   -vr, --video-reconnect      auto-reconnect video (default)
   -nvr, --no-video-reconnect  do not auto-reconnect video

default/forge_project.cfg

@@ -51,8 +51,6 @@ UNIFORM_STATE_PREFIX=iState
 UNIFORM_ACTIVE_PREFIX=iActive
 # Input X format raw integer value
 UNIFORM_IN_FORMAT_PREFIX=iInputFormat
-# Input X should use swap texture or not (0/1)
-UNIFORM_IN_SWAP_PREFIX=iInputSwap
 
 # --- uniform vec2 ---
 
@@ -106,9 +104,6 @@ IN_COUNT=2
 # To which texture will be bound video device X
 IN_1_OUT=1
 IN_2_OUT=2
-# To which texture will be bound swap buffers (for double-buffering)
-IN_1_SWAP_OUT=3
-IN_2_SWAP_OUT=4
 
 # === FRAGMENT SHADERS
 # Fragment shaders will be read from the CLI directory as "fragX.glsl"

src/args.c

@@ -32,6 +32,7 @@ static void print_help(int status_code) {
 #ifdef VIDEO_IN
       "[-vi=FILE] "
       "[-vs=SIZE] "
+      "[-vb=COUNT] "
       "[-vr / -nvr] "
 #endif /* VIDEO_IN */
       "[-is=SIZE] "
@@ -63,6 +64,8 @@ static void print_help(int status_code) {
 #ifdef VIDEO_IN
       "  -vi, --video-in             path to video capture device (multiple "
       "allowed)\n"
+      "  -vb, --video-buffers        number of video buffers to use (default: "
+      "2)\n"
       "  -vs, --video-size           video capture desired height (default: "
       "internal texture height)\n"
       "  -vr, --video-reconnect      auto-reconnect video (default)\n"
@@ -134,9 +137,12 @@ void args_parse(Parameters *params, int argc, char **argv) {
   params->demo = false;
   params->auto_random = false;
   params->auto_random_cycle = 4;
+#ifdef VIDEO_IN
   params->video_in.length = 0;
+  params->video_buffers = 2;
   params->video_size = 0;
   params->video_reconnect = true;
+#endif /* VIDEO_IN */
   params->internal_size = 720;
   params->load_state = true;
   params->save_state = true;
@@ -184,38 +190,6 @@ void args_parse(Parameters *params, int argc, char **argv) {
       if (params->auto_random_cycle == 0) {
         invalid_value(arg, value);
       }
-    } else if (is_arg(arg, "-vi") || is_arg(arg, "--video-in")) {
-#ifdef VIDEO_IN
-      if (params->video_in.length == MAX_VIDEO) {
-        log_error("maximum video input reached");
-        exit(EXIT_FAILURE);
-      }
-      strlcpy(params->video_in.values[params->video_in.length++], value,
-              STR_LEN);
-#else
-      invalid_arg(arg);
-#endif /* VIDEO_IN */
-    } else if (is_arg(arg, "-vs") || is_arg(arg, "--video-size")) {
-#ifdef VIDEO_IN
-      params->video_size = parse_uint(arg, value);
-      if (params->video_size == 0) {
-        invalid_value(arg, value);
-      }
-#else
-      invalid_arg(arg);
-#endif /* VIDEO_IN */
-    } else if (is_arg(arg, "-vr") || is_arg(arg, "--video-reconnect")) {
-#ifdef VIDEO_IN
-      params->video_reconnect = true;
-#else
-      invalid_arg(arg);
-#endif /* VIDEO_IN */
-    } else if (is_arg(arg, "-nvr") || is_arg(arg, "--no-video-reconnect")) {
-#ifdef VIDEO_IN
-      params->video_reconnect = false;
-#else
-      invalid_arg(arg);
-#endif /* VIDEO_IN */
     } else if (is_arg(arg, "-is") || is_arg(arg, "--internal-size")) {
       params->internal_size = parse_uint(arg, value);
       if (params->internal_size == 0) {
@@ -238,7 +212,34 @@ void args_parse(Parameters *params, int argc, char **argv) {
     } else if (is_arg(arg, "-tf") || is_arg(arg, "--trace-fps")) {
       params->trace_fps = true;
     } else {
+#ifdef VIDEO_IN
+      if (is_arg(arg, "-vi") || is_arg(arg, "--video-in")) {
+        if (params->video_in.length == MAX_VIDEO) {
+          log_error("maximum video input reached");
+          exit(EXIT_FAILURE);
+        }
+        strlcpy(params->video_in.values[params->video_in.length++], value,
+                STR_LEN);
+      } else if (is_arg(arg, "-vb") || is_arg(arg, "--video-buffers")) {
+        params->video_buffers = parse_uint(arg, value);
+        if (params->video_buffers == 0) {
+          invalid_value(arg, value);
+        }
+      } else if (is_arg(arg, "-vs") || is_arg(arg, "--video-size")) {
+        params->video_size = parse_uint(arg, value);
+        if (params->video_size == 0) {
+          invalid_value(arg, value);
+        }
+      } else if (is_arg(arg, "-vr") || is_arg(arg, "--video-reconnect")) {
+        params->video_reconnect = true;
+      } else if (is_arg(arg, "-nvr") || is_arg(arg, "--no-video-reconnect")) {
+        params->video_reconnect = false;
+      } else {
+        invalid_arg(arg);
+      }
+#else
       invalid_arg(arg);
+#endif /* VIDEO_IN */
     }
   }
 
@@ -247,8 +248,9 @@ void args_parse(Parameters *params, int argc, char **argv) {
     log_error("monitor screen cannot be the same as output screen");
     exit(EXIT_FAILURE);
   }
-
+#ifdef VIDEO_IN
   if (params->video_size == 0) {
     params->video_size = params->internal_size;
   }
+#endif /* VIDEO_IN */
 }

src/forge.c

@@ -70,7 +70,7 @@ static void init_context() {
   memset(context.input_resolutions, 0, sizeof(context.input_resolutions));
   memset(context.input_formats, 0, sizeof(context.input_formats));
   memset(context.input_fps, 0, sizeof(context.input_fps));
-  memset(context.input_swap, 0, sizeof(context.input_swap));
+  memset(context.input_index, 0, sizeof(context.input_index));
 #endif /* VIDEO_IN */
 }
 
@@ -85,7 +85,7 @@ static void init_inputs() {
 
   for (unsigned int i = 0; i < init_params.video_in.length; i++) {
     video_init(&video_captures.values[i], init_params.video_in.values[i],
-               init_params.video_size);
+               init_params.video_size, init_params.video_buffers);
 
     if (!video_captures.values[i].error) {
       context.input_resolutions[i][0] = video_captures.values[i].width;
@@ -121,7 +121,7 @@ background_reconnect_video_captures(__attribute__((unused)) void *args) {
       if (video_captures.values[i].disconnected) {
         video_free(&video_captures.values[i]);
         video_init(&video_captures.values[i], init_params.video_in.values[i],
-                   init_params.video_size);
+                   init_params.video_size, init_params.video_buffers);
 
         if (!video_captures.values[i].error) {
           context.input_resolutions[i][0] = video_captures.values[i].width;
@@ -292,7 +292,8 @@ static bool init(const Parameters *params) {
   }
 
 #ifdef VIDEO_IN
-  shaders_link_inputs(&program, &project, &video_captures);
+  shaders_link_inputs(&program, &project, &video_captures,
+                      init_params.video_buffers);
 #endif /* VIDEO_IN */
 
   if (program.error) {

src/shaders.c

@@ -191,18 +191,20 @@ static void rebind_textures(const ShaderProgram *program) {
 #ifdef VIDEO_IN
 static bool link_input_to_texture(ShaderProgram *program, VideoCapture *input,
                                   unsigned int input_index,
-                                  unsigned int texture_index, bool swap,
-                                  bool reload) {
+                                  unsigned int sub_index, bool reload) {
+  unsigned int texture_index =
+      program->tex_count + input_index * program->sub_video_count + sub_index;
+
   if (reload) {
     glDeleteTextures(1, program->textures + texture_index);
     if (check_glerror(program, "link_input_to_texture/glDeleteTextures")) {
       return false;
     }
+  }
 
-    glGenTextures(1, program->textures + texture_index);
-    if (check_glerror(program, "link_input_to_texture/glGenTextures")) {
-      return false;
-    }
+  glGenTextures(1, program->textures + texture_index);
+  if (check_glerror(program, "link_input_to_texture/glGenTextures")) {
+    return false;
   }
 
   EGLImageKHR dma_image;
@@ -217,7 +219,7 @@ static bool link_input_to_texture(ShaderProgram *program, VideoCapture *input,
                                 EGL_LINUX_DRM_FOURCC_EXT,
                                 input->pixelformat,
                                 EGL_DMA_BUF_PLANE0_FD_EXT,
-                                swap ? input->exp_fd_swap : input->exp_fd,
+                                input->exp_fd[sub_index],
                                 EGL_DMA_BUF_PLANE0_OFFSET_EXT,
                                 0,
                                 EGL_DMA_BUF_PLANE0_PITCH_EXT,
@@ -230,11 +232,8 @@ static bool link_input_to_texture(ShaderProgram *program, VideoCapture *input,
     return false;
   }
 
-  if (swap) {
-    program->dma_images_swap[input_index] = dma_image;
-  } else {
-    program->dma_images[input_index] = dma_image;
-  }
+  program->dma_images[input_index * program->sub_video_count + sub_index] =
+      dma_image;
 
   glActiveTexture(GL_TEXTURE0 + texture_index);
   if (check_glerror(program, "link_input_to_texture/glActiveTexture")) {
@@ -259,33 +258,35 @@ static bool link_input_to_texture(ShaderProgram *program, VideoCapture *input,
     return false;
   }
 
-  log_info("Texture %d linked to %s", texture_index, input->name);
+  log_info("Texture %d linked to %s[%d]", texture_index, input->name,
+           sub_index);
 
   return true;
 }
 
 static bool init_input(ShaderProgram *program, const ConfigFile *config,
-                       VideoCaptureArray *inputs, unsigned int i, bool reload) {
+                       VideoCaptureArray *inputs, unsigned int input_index,
+                       bool reload) {
   unsigned int tex_i;
+  unsigned int sub_index;
   char name[STR_LEN];
 
-  if (i < inputs->length && !inputs->values[i].error) {
-    snprintf(name, STR_LEN, "IN_%d_OUT", i + 1);
+  if (input_index < inputs->length && input_index < program->in_count &&
+      !inputs->values[input_index].error) {
+    snprintf(name, STR_LEN, "IN_%d_OUT", input_index + 1);
     tex_i = config_file_get_int(config, name, 0);
-    if (!link_input_to_texture(program, &inputs->values[i], i, tex_i, false,
-                               reload)) {
-      return false;
-    }
-    if (inputs->values[i].with_swap) {
-      snprintf(name, STR_LEN, "IN_%d_SWAP_OUT", i + 1);
-      tex_i = config_file_get_int(config, name, 0);
-      if (!link_input_to_texture(program, &inputs->values[i], i, tex_i, true,
-                                 reload)) {
+    for (sub_index = 0; sub_index < inputs->values[input_index].buf_count;
+         sub_index++) {
+      if (!link_input_to_texture(program, &inputs->values[input_index],
+                                 input_index, sub_index, reload)) {
         return false;
       }
     }
+    program->input_tex_map[input_index] = tex_i;
+    program->tex_map[tex_i] =
+        program->tex_count + input_index * program->sub_video_count;
   } else {
-    log_warn("Cannot link input %d", i + 1);
+    log_warn("Cannot link input %d", input_index + 1);
   }
   return true;
 }
@@ -535,13 +536,6 @@ static bool init_single_program(ShaderProgram *program, unsigned int i,
         glGetUniformLocation(program->programs[i], name);
   }
 
-  prefix = config_file_get_str(config, "UNIFORM_IN_SWAP_PREFIX", "iInputSwap");
-  for (unsigned int j = 0; j < program->in_count; j++) {
-    snprintf(name, STR_LEN, "%s%d", prefix, j + 1);
-    program->iinswap_locations[i * program->in_count + j] =
-        glGetUniformLocation(program->programs[i], name);
-  }
-
   prefix = config_file_get_str(config, "UNIFORM_SEED_PREFIX", "iSeed");
   for (unsigned int j = 0; j < program->frag_count; j++) {
     snprintf(name, STR_LEN, "%s%d", prefix, j + 1);
@@ -650,8 +644,7 @@ static void update_viewport(ShaderProgram *program, const Context *context) {
 
       glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, context->tex_resolution[0],
                    context->tex_resolution[1], 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
-      check_glerror_ro(
-          "update_viewport/glTexImage2D"); // TODO dont remap input textures
+      check_glerror_ro("update_viewport/glTexImage2D");
     }
     program->last_resolution[0] = context->resolution[0];
     program->last_resolution[1] = context->resolution[1];
@@ -736,8 +729,6 @@ static void use_program(const ShaderProgram *program, int i, bool output,
                      context->input_formats[j]);
     write_uniform_1i(program->iinfps_locations[i * program->in_count + j],
                      context->input_fps[j]);
-    write_uniform_1i(program->iinswap_locations[i * program->in_count + j],
-                     context->input_swap[j] ? 1 : 0);
   }
 
 #endif /* VIDEO_IN */
@@ -781,10 +772,9 @@ static void use_program(const ShaderProgram *program, int i, bool output,
   }
 
   // set GL_TEXTURE(X) to uniform sampler2D texX
-  // TODO perform input swap here
   for (unsigned int j = 0; j < program->tex_count; j++) {
     write_uniform_1i(program->textures_locations[i * program->tex_count + j],
-                     j);
+                     program->tex_map[j]);
   }
 
   // draw output
@@ -793,11 +783,16 @@ static void use_program(const ShaderProgram *program, int i, bool output,
 
 void shaders_init(ShaderProgram *program, const Project *project,
                   const Context *context, bool rebind) {
+  unsigned int i;
   if (!rebind) {
     program->error = false;
     program->last_resolution[0] = context->resolution[0];
     program->last_resolution[1] = context->resolution[1];
     program->tex_count = config_file_get_int(&project->config, "TEX_COUNT", 9);
+    memset(program->tex_map, 0, sizeof(program->tex_map));
+    for (i = 0; i < program->tex_count; i++) {
+      program->tex_map[i] = i;
+    }
     program->frag_count = project->frag_count;
     program->frag_output_index =
         config_file_get_int(&project->config, "FRAG_OUTPUT", 1) - 1;
@@ -812,7 +807,7 @@ void shaders_init(ShaderProgram *program, const Project *project,
 
 #ifdef VIDEO_IN
     memset(program->dma_images, 0, sizeof(program->dma_images));
-    memset(program->dma_images_swap, 0, sizeof(program->dma_images_swap));
+    memset(program->input_tex_map, 0, sizeof(program->input_tex_map));
 #endif /* VIDEO_IN */
 
     if (!init_gl(program)) {
@@ -848,31 +843,50 @@ void shaders_init(ShaderProgram *program, const Project *project,
 #ifdef VIDEO_IN
 
 void shaders_relink_input(ShaderProgram *program, const Project *project,
-                          VideoCaptureArray *inputs, unsigned int i) {
-  // shaders_free_input(program, i);
-  init_input(program, &project->config, inputs, i, true);
+                          VideoCaptureArray *inputs, unsigned int input_index) {
+  shaders_free_input(program, input_index);
+  init_input(program, &project->config, inputs, input_index, true);
 }
 
 void shaders_link_inputs(ShaderProgram *program, const Project *project,
-                         VideoCaptureArray *inputs) {
-  for (unsigned int i = 0; i < program->in_count; i++) {
+                         VideoCaptureArray *inputs, unsigned int buffer_count) {
+  unsigned int i;
+  program->sub_video_count = buffer_count;
+  for (i = 0; i < program->in_count; i++) {
     init_input(program, &project->config, inputs, i, false);
   }
 }
 
 void shaders_free_input(ShaderProgram *program, unsigned int input_index) {
-  if (program->dma_images[input_index] != EGL_NO_IMAGE_KHR) {
-    eglDestroyImageKHR(program->egl_display, program->dma_images[input_index]);
-    program->dma_images[input_index] = EGL_NO_IMAGE_KHR;
-  }
-  if (program->dma_images_swap[input_index] != EGL_NO_IMAGE_KHR) {
-    eglDestroyImageKHR(program->egl_display,
-                       program->dma_images_swap[input_index]);
-    program->dma_images_swap[input_index] = EGL_NO_IMAGE_KHR;
+  unsigned int sub_index;
+  for (sub_index = 0; sub_index < program->sub_video_count; sub_index++) {
+    if (program->dma_images[input_index * program->sub_video_count +
+                            sub_index] != EGL_NO_IMAGE_KHR) {
+      eglDestroyImageKHR(
+          program->egl_display,
+          program
+              ->dma_images[input_index * program->sub_video_count + sub_index]);
+      program->dma_images[input_index * program->sub_video_count + sub_index] =
+          EGL_NO_IMAGE_KHR;
+    }
   }
   check_eglerror_ro("shaders_free_input/eglDestroyImageKHR");
 }
 
+static void update_inputs_tex_map(ShaderProgram *program,
+                                  const Context *context) {
+  unsigned int i;
+  unsigned int tex_i;
+  for (i = 0; i < program->in_count; i++) {
+    if (context->input_formats[i] != 0) {
+      tex_i = program->input_tex_map[i];
+      program->tex_map[tex_i] = program->tex_count +
+                                i * program->sub_video_count +
+                                context->input_index[i];
+    }
+  }
+}
+
 #endif /* VIDEO_IN */
 
 void shaders_update(ShaderProgram *program, const File *fragment_shader,
@@ -887,6 +901,10 @@ void shaders_update(ShaderProgram *program, const File *fragment_shader,
 
 void shaders_compute(ShaderProgram *program, const Context *context,
                      bool monitor, bool output_only) {
+#ifdef VIDEO_IN
+  update_inputs_tex_map(program, context);
+#endif /* VIDEO_IN */
+
   if (!output_only) {
     glBindVertexArray(program->vertex_array[0]);
 
@@ -923,6 +941,12 @@ void shaders_free(const ShaderProgram *program) {
   glDeleteTextures(program->tex_count, program->textures);
   check_glerror_ro("shaders_free/glDeleteTextures");
 
+#ifdef VIDEO_IN
+  glDeleteTextures(program->in_count * program->sub_video_count,
+                   program->textures + program->tex_count);
+  check_glerror_ro("shaders_free/glDeleteTextures");
+#endif
+
   glDeleteBuffers(1, &program->vertex_buffer);
   check_glerror_ro("shaders_free/glDeleteBuffers");
 }

src/shaders.h

@@ -12,7 +12,7 @@ void shaders_relink_input(ShaderProgram *program, const Project *project,
                           VideoCaptureArray *inputs, unsigned int i);
 
 void shaders_link_inputs(ShaderProgram *program, const Project *project,
-                         VideoCaptureArray *inputs);
+                         VideoCaptureArray *inputs, unsigned int buffer_count);
 
 void shaders_free_input(ShaderProgram *program, unsigned int input_index);
 

src/types.h

@@ -45,10 +45,13 @@ typedef struct Parameters {
   bool demo;
   bool auto_random;
   unsigned int auto_random_cycle;
+#ifdef VIDEO_IN
   StringArray video_in;
+  unsigned int video_buffers;
   unsigned int video_size;
-  unsigned int internal_size;
   bool video_reconnect;
+#endif /* VIDEO_IN */
+  unsigned int internal_size;
   bool load_state;
   bool save_state;
   bool midi_reconnect;
@@ -85,6 +88,7 @@ typedef struct ShaderProgram {
   GLuint vertex_array[2];
 
   unsigned int tex_count;
+  unsigned int tex_map[ARRAY_SIZE];
   GLuint textures[ARRAY_SIZE];
 
   unsigned int frag_count;
@@ -105,7 +109,6 @@ typedef struct ShaderProgram {
   GLuint iinres_locations[ARRAY_SIZE];
   GLuint iinfmt_locations[ARRAY_SIZE];
   GLuint iinfps_locations[ARRAY_SIZE];
-  GLuint iinswap_locations[ARRAY_SIZE];
   GLuint idemo_locations[ARRAY_SIZE];
   GLuint iautorand_locations[ARRAY_SIZE];
   GLuint iautorandcycle_locations[ARRAY_SIZE];
@@ -130,9 +133,10 @@ typedef struct ShaderProgram {
 
   unsigned int in_count;
 #ifdef VIDEO_IN
+  unsigned int sub_video_count;
+  unsigned int input_tex_map[MAX_VIDEO];
   EGLDisplay egl_display;
   EGLImageKHR dma_images[MAX_VIDEO];
-  EGLImageKHR dma_images_swap[MAX_VIDEO];
 #endif /* VIDEO_IN */
 } ShaderProgram;
 
@@ -163,7 +167,7 @@ typedef struct Context {
   vec2 input_resolutions[MAX_VIDEO];
   unsigned int input_formats[MAX_VIDEO];
   unsigned int input_fps[MAX_VIDEO];
-  bool input_swap[MAX_VIDEO];
+  unsigned int input_index[MAX_VIDEO];
 #endif /* VIDEO_IN */
   double time;
   Tempo tempo;
@@ -190,17 +194,15 @@ typedef struct VideoCapture {
   _Atomic bool error;
   _Atomic bool disconnected;
   _Atomic bool needs_reload;
-  bool with_swap;
-  _Atomic bool swap;
+  unsigned int buf_count;
+  unsigned int buf_index;
   int fd;
-  int exp_fd;
-  int exp_fd_swap;
+  int exp_fd[ARRAY_SIZE];
   unsigned int width;
   unsigned int height;
   unsigned int pixelformat;
   unsigned int bytesperline;
-  struct v4l2_buffer buf;
-  struct v4l2_buffer buf_swap;
+  struct v4l2_buffer buf[ARRAY_SIZE];
 } VideoCapture;
 
 typedef struct VideoCaptureArray {

src/video.c

@@ -192,14 +192,15 @@ static bool set_format(VideoCapture *video_capture) {
   return true;
 }
 
-static bool request_buffers(VideoCapture *video_capture) {
+static bool request_buffers(VideoCapture *video_capture,
+                            unsigned int buffer_count) {
   struct v4l2_requestbuffers reqbuf;
 
   memset(&reqbuf, 0, sizeof(reqbuf));
 
   reqbuf.type = buf_type;
   reqbuf.memory = V4L2_MEMORY_MMAP;
-  reqbuf.count = 2; // TODO buffer array with count from parameters
+  reqbuf.count = buffer_count;
 
   if (ioctl(video_capture->fd, VIDIOC_REQBUFS, &reqbuf) == -1) {
     ioctl_error(video_capture, "VIDIOC_REQBUFS",
@@ -209,7 +210,7 @@ static bool request_buffers(VideoCapture *video_capture) {
 
   log_info("(%s) V4L2 Buffer Count:  %d", video_capture->name, reqbuf.count);
 
-  video_capture->with_swap = reqbuf.count > 1;
+  video_capture->buf_count = reqbuf.count;
 
   return true;
 }
@@ -239,16 +240,15 @@ static bool export_buffer(VideoCapture *video_capture, int *fd,
 }
 
 static bool export_buffers(VideoCapture *video_capture) {
-  bool result;
+  unsigned int i;
 
-  result = export_buffer(video_capture, &video_capture->exp_fd, 0);
-
-  if (result && video_capture->with_swap) {
-    result =
-        result && export_buffer(video_capture, &video_capture->exp_fd_swap, 1);
+  for (i = 0; i < video_capture->buf_count; i++) {
+    if (!export_buffer(video_capture, &video_capture->exp_fd[i], i)) {
+      return false;
+    }
   }
 
-  return result;
+  return true;
 }
 
 static bool open_stream(VideoCapture *video_capture) {
@@ -274,10 +274,10 @@ static void create_image_buffer(const VideoCapture *video_capture,
 }
 
 static void create_image_buffers(VideoCapture *video_capture) {
-  create_image_buffer(video_capture, &video_capture->buf, 0);
+  unsigned int i;
 
-  if (video_capture->with_swap) {
-    create_image_buffer(video_capture, &video_capture->buf_swap, 1);
+  for (i = 0; i < video_capture->buf_count; i++) {
+    create_image_buffer(video_capture, &video_capture->buf[i], i);
   }
 }
 
@@ -286,31 +286,26 @@ static void close_stream(const VideoCapture *video_capture) {
 }
 
 static unsigned int read_video(VideoCapture *video_capture) {
-  unsigned int result;
   struct v4l2_capability cap;
 
-  result = 0;
+  if (ioctl(video_capture->fd, VIDIOC_DQBUF,
+            &video_capture->buf[video_capture->buf_index]) != -1) {
+    ioctl(video_capture->fd, VIDIOC_QBUF,
+          &video_capture->buf[video_capture->buf_index]);
+    video_capture->buf_index =
+        (video_capture->buf_index + 1) % video_capture->buf_count;
+    return true;
+  }
 
-  if ((video_capture->swap || !video_capture->with_swap) &&
-      ioctl(video_capture->fd, VIDIOC_DQBUF, &video_capture->buf) != -1) {
-    ioctl(video_capture->fd, VIDIOC_QBUF, &video_capture->buf);
-
-    result = 1;
-  } else if (!video_capture->swap && video_capture->with_swap &&
-             ioctl(video_capture->fd, VIDIOC_DQBUF, &video_capture->buf_swap) !=
-                 -1) {
-    ioctl(video_capture->fd, VIDIOC_QBUF, &video_capture->buf_swap);
-
-    result = 2;
-  } else if (ioctl(video_capture->fd, VIDIOC_QUERYCAP, &cap) == -1) {
+  if (ioctl(video_capture->fd, VIDIOC_QUERYCAP, &cap) == -1) {
     video_capture->error = true;
   }
 
-  return result;
+  return false;
 }
 
 void video_init(VideoCapture *video_capture, const char *name,
-                unsigned int preferred_height) {
+                unsigned int preferred_height, unsigned int buffer_count) {
   open_device(video_capture, name);
 
   if (video_capture->error) {
@@ -329,7 +324,7 @@ void video_init(VideoCapture *video_capture, const char *name,
     return;
   }
 
-  if (!request_buffers(video_capture)) {
+  if (!request_buffers(video_capture, buffer_count)) {
     return;
   }
 
@@ -352,14 +347,15 @@ void *video_background_read(void *args) {
   bool trace_fps = process_args->trace_fps;
   Timer timer;
   double fps;
-  unsigned int video_result;
+  bool result;
 
   log_info("(%s) background acquisition started", video_capture->name);
   timer_init(&timer, 30);
 
   while (!context->stop && !video_capture->error) {
-    video_result = read_video(video_capture);
-    if (video_result > 0 && timer_inc(&timer)) {
+    result = read_video(video_capture);
+
+    if (result && timer_inc(&timer)) {
       fps = timer_reset(&timer);
 
       context->input_fps[input_index] = (unsigned int)round(fps);
@@ -367,9 +363,9 @@ void *video_background_read(void *args) {
         log_trace("(%s) %.2ffps", video_capture->name, fps);
       }
     }
-    if (video_result > 0) {
-      context->input_swap[input_index] = video_capture->swap =
-          video_result == 2;
+
+    if (result) {
+      context->input_index[input_index] = video_capture->buf_index;
     }
   }
   if (context->stop) {
@@ -385,13 +381,14 @@ void *video_background_read(void *args) {
 }
 
 void video_free(const VideoCapture *video_capture) {
+  unsigned int i;
+
   close_stream(video_capture);
-  if (video_capture->exp_fd != -1) {
-    close(video_capture->exp_fd);
-  }
-  if (video_capture->exp_fd_swap != -1) {
-    close(video_capture->exp_fd_swap);
+
+  for (i = 0; i < video_capture->buf_count; i++) {
+    close(video_capture->exp_fd[i]);
   }
+
   if (video_capture->fd != -1) {
     close(video_capture->fd);
   }

src/video.h

@@ -6,7 +6,7 @@
 #ifdef VIDEO_IN
 
 void video_init(VideoCapture *video_capture, const char *name,
-                unsigned int preferred_height);
+                unsigned int preferred_height, unsigned int buffer_count);
 
 void *video_background_read(void *args);