feat: double buffered video input

DEVELOPMENT.md

@@ -126,6 +126,7 @@ make -f Makefile.dev release-arch
   - [x] Monitor improvements
   - [ ] Ignore some values in auto random
   - [x] build without video in
+  - [ ] Auto discover video devices
   - [ ] Update README monitor/keymap
   - [ ] Auto reconnect midi input
   - [ ] Auto reconnect video device
@@ -136,4 +137,4 @@ make -f Makefile.dev release-arch
   - [ ] Play from record text file
 - [ ] Fixes
   - [ ] Try to write NanoKontrol config
-  - [ ] Investigate video device fps loss (bad unregister ?)
+  - [x] Investigate video device fps loss (bad unregister ?)

README.md

@@ -479,8 +479,6 @@ Unfortunately, V4L2 is very slow compared to driver-specific decoding.
 
 You can check your device real FPS on [V4L2 UCP](https://github.com/HedgeHawk/v4l2ucp) or [GTK UVC Viewer](https://github.com/jaswdr/guvcview).
 
-Sadly, OpenEGL doesn't support double-buffered DMA buffers so FPS in FORGE may be halved.
-
 ### My video feed got strange lines
 
 You need to decode the [V4L2 YUYV format](https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-yuyv.html).

default/forge_project.cfg

@@ -51,6 +51,8 @@ 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 ---
 
@@ -93,7 +95,7 @@ SUB_2_PREFIX=fx_
 
 
 # Total number of internal textures
-TEX_COUNT=10
+TEX_COUNT=12
 
 # === VIDEO DEVICES
 # Video devices will be read from CLI arguments
@@ -104,10 +106,12 @@ 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"
-# Special shader "frag0.glsl" will be prepend to each one
 
 # Prefix of fragment shaders to detect
 FRAG_FILE_PREFIX=frag
@@ -116,13 +120,13 @@ FRAG_FILE_PREFIX=frag
 FRAG_COUNT=10
 
 # To which texture will the shader fragX.glsl will render to
-FRAG_1_OUT=3
+FRAG_1_OUT=5
-FRAG_2_OUT=4
+FRAG_2_OUT=6
-FRAG_3_OUT=5
+FRAG_3_OUT=7
-FRAG_4_OUT=6
+FRAG_4_OUT=8
-FRAG_5_OUT=7
+FRAG_5_OUT=9
-FRAG_6_OUT=8
+FRAG_6_OUT=10
-FRAG_7_OUT=9
+FRAG_7_OUT=11
 FRAG_8_OUT=0
 # Which fragment shader renders to output window
 FRAG_OUTPUT=9

default/frag1.glsl

@@ -2,8 +2,8 @@
 
 // VIDEO 1
 // -----------
-// IN: 1 (RAW IN A)
+// IN: 1+3 (RAW IN A)
-// OUT: 3 (IN A)
+// OUT: 5 (IN A)
 
 in vec2 vUV;
 out vec4 fragColor;
@@ -12,14 +12,18 @@ out vec4 fragColor;
 
 uniform sampler2D iTex0;
 uniform sampler2D iTex1;
+uniform sampler2D iTex3;
 uniform int iInputFormat1;
+uniform int iInputSwap1;
 uniform vec2 iInputResolution1;
 
 void main() {
     if (iInputFormat1 == YUYV_FOURCC) {
-        fragColor = yuyvTex(iTex1, vUV, int(iInputResolution1.x));
+        if (iInputSwap1 > 0) {
-    } else if (iInputResolution1.x > 0) {
+            fragColor = yuyvTex(iTex3, vUV, int(iInputResolution1.x));
-        fragColor = texture(iTex1, vUV);
+        } else {
+            fragColor = yuyvTex(iTex1, vUV, int(iInputResolution1.x));
+        }
     } else {
         fragColor = texture(iTex0, vUV);
     }

default/frag10.glsl

@@ -9,15 +9,13 @@ out vec4 fragColor;
 #include inc_debug.glsl
 
 uniform sampler2D iTex0;
-uniform sampler2D iTex1;
-uniform sampler2D iTex2;
-uniform sampler2D iTex3;
-uniform sampler2D iTex4;
 uniform sampler2D iTex5;
 uniform sampler2D iTex6;
 uniform sampler2D iTex7;
 uniform sampler2D iTex8;
 uniform sampler2D iTex9;
+uniform sampler2D iTex10;
+uniform sampler2D iTex11;
 uniform int iFPS;
 uniform int iInputFPS1;
 uniform int iInputFPS2;
@@ -52,14 +50,14 @@ void main() {
 
     vec4 c = vec4(0);
     
-    c += s(uv2,1,2) * texture(iTex5, uv2);
+    c += s(uv2,1,2) * texture(iTex7, uv2);
-    c += s(uv2,2,2) * texture(iTex7, uv2);
+    c += s(uv2,2,2) * texture(iTex9, uv2);
 
-    c += s(uv2,1,0) * texture(iTex6, uv2);
+    c += s(uv2,1,0) * texture(iTex8, uv2);
-    c += s(uv2,2,0) * texture(iTex8, uv2);
+    c += s(uv2,2,0) * texture(iTex10, uv2);
 
     c += s(uv2,0,1) * debug(mod(uv2, 1));
-    c += s(uv2,1,1) * texture(iTex9, uv2);
+    c += s(uv2,1,1) * texture(iTex11, uv2);
     c += s(uv2,2,1) * texture(iTex0, uv2);
 
     float sel = 0;
@@ -79,7 +77,7 @@ void main() {
     t += write_5(uv3, vec2(-37,28), texts[0]);
     
     if (iInputResolution1.x > 0) {
-        c += s(uv2,0,2) * texture(iTex3, uv2);
+        c += s(uv2,0,2) * texture(iTex5, uv2);
         f += rect(uv3, vec2(-35, 26.75), vec2(2.8, 0.7));
         t += write_int(uv3, vec2(-37.6,26.1), iInputFPS1, 2);
         t += write_5(uv3, vec2(-35.1,26.1), texts[8]);
@@ -92,7 +90,7 @@ void main() {
     t += write_5(uv3, vec2(-37,-12), texts[1]);
 
     if (iInputResolution2.x > 0) {
-        c += s(uv2,0,0) * texture(iTex4, uv2);
+        c += s(uv2,0,0) * texture(iTex6, uv2);
         f += rect(uv3, vec2(-35, -13.25), vec2(2.8, 0.7));
         t += write_int(uv3, vec2(-37.6,-13.9), iInputFPS2, 2);
         t += write_5(uv3, vec2(-35.1,-13.9), texts[8]);

default/frag2.glsl

@@ -2,8 +2,8 @@
 
 // VIDEO 2
 // -----------
-// IN: 2 (RAW IN B)
+// IN: 2+4 (RAW IN B)
-// OUT: 4 (IN B)
+// OUT: 6 (IN B)
 
 in vec2 vUV;
 out vec4 fragColor;
@@ -12,14 +12,18 @@ out vec4 fragColor;
 
 uniform sampler2D iTex0;
 uniform sampler2D iTex2;
+uniform sampler2D iTex4;
 uniform int iInputFormat2;
+uniform int iInputSwap2;
 uniform vec2 iInputResolution2;
 
 void main() {
     if (iInputFormat2 == YUYV_FOURCC) {
-        fragColor = yuyvTex(iTex2, vUV, int(iInputResolution2.x));
+        if (iInputSwap2 > 0) {
-    } else if (iInputResolution2.x > 0) {
+            fragColor = yuyvTex(iTex4, vUV, int(iInputResolution2.x));
-        fragColor = texture(iTex2, vUV);
+        } else {
+            fragColor = yuyvTex(iTex2, vUV, int(iInputResolution2.x));
+        }
     } else {
         fragColor = texture(iTex0, vUV);
     }

default/frag3.glsl

@@ -3,7 +3,7 @@
 
 // SRC A
 // -----------
-// OUT: 5 (FX A)
+// OUT: 7 (FX A)
 
 in vec2 vUV;
 out vec4 fragColor;

default/frag4.glsl

@@ -2,7 +2,7 @@
 
 // SRC B
 // -----------
-// OUT: 6 (FX B)
+// OUT: 8 (FX B)
 
 in vec2 vUV;
 out vec4 fragColor;

default/frag5.glsl

@@ -2,20 +2,20 @@
 
 // FX A
 // -------------
-// IN: 5 (SRC A)
+// IN: 7 (SRC A)
-// IN: 7 (FX A)
+// IN: 9 (FX A)
-// OUT: 7 (A+B)
+// OUT: 9 (A+B)
 
 in vec2 vUV;
 out vec4 fragColor;
 
 #include inc_fx.glsl
 
-uniform sampler2D iTex5;
 uniform sampler2D iTex7;
+uniform sampler2D iTex9;
 uniform int iSeed5;
 uniform vec3 iMidi2_1[7];
 
 void main() {
-    fragColor = fx_stage(vUV, iTex5, iTex7, iSeed5, iMidi2_1[0], iMidi2_1[1].xy, iMidi2_1[2], iMidi2_1[3].xy, iMidi2_1[4], iMidi2_1[5].xy, iMidi2_1[6]);
+    fragColor = fx_stage(vUV, iTex7, iTex9, iSeed5, iMidi2_1[0], iMidi2_1[1].xy, iMidi2_1[2], iMidi2_1[3].xy, iMidi2_1[4], iMidi2_1[5].xy, iMidi2_1[6]);
 }

default/frag6.glsl

@@ -2,20 +2,20 @@
 
 // FX B
 // -------------
-// IN: 6 (SRC B)
+// IN: 8 (SRC B)
-// IN: 8 (FX B)
+// IN: 10 (FX B)
-// OUT: 8 (A+B)
+// OUT: 10 (A+B)
 
 in vec2 vUV;
 out vec4 fragColor;
 
 #include inc_fx.glsl
 
-uniform sampler2D iTex6;
 uniform sampler2D iTex8;
+uniform sampler2D iTex10;
 uniform int iSeed6;
 uniform vec3 iMidi2_2[7];
 
 void main() {
-    fragColor = fx_stage(vUV, iTex6, iTex8, iSeed6, iMidi2_2[0], iMidi2_2[1].xy, iMidi2_2[2], iMidi2_2[3].xy, iMidi2_2[4], iMidi2_2[5].xy, iMidi2_2[6]);
+    fragColor = fx_stage(vUV, iTex8, iTex10, iSeed6, iMidi2_2[0], iMidi2_2[1].xy, iMidi2_2[2], iMidi2_2[3].xy, iMidi2_2[4], iMidi2_2[5].xy, iMidi2_2[6]);
 }

default/frag7.glsl

@@ -2,9 +2,9 @@
 
 // A+B
 // ------------
-// IN: 7 (FX A)
+// IN: 9 (FX A)
-// IN: 8 (FX B)
+// IN: 10 (FX B)
-// OUT: 9 (MFX)
+// OUT: 11 (MFX)
 
 in vec2 vUV;
 out vec4 fragColor;
@@ -13,8 +13,8 @@ out vec4 fragColor;
 #include inc_functions.glsl
 
 uniform int iDemo;
-uniform sampler2D iTex7;
+uniform sampler2D iTex9;
-uniform sampler2D iTex8;
+uniform sampler2D iTex10;
 uniform int iSeed7;
 uniform vec3 iMidi3_1[2];
 
@@ -22,8 +22,8 @@ void main() {
     float mix_value = magic(iMidi3_1[1].xy, vec3(1, 0, 0), iSeed7);
     bool mix_type = magic_trigger(vec3(iMidi3_1[0].x, 0, 0), iSeed7 + 10);
 
-    vec4 color_a = texture(iTex7, vUV);
+    vec4 color_a = texture(iTex9, vUV);
-    vec4 color_b = texture(iTex8, vUV);
+    vec4 color_b = texture(iTex10, vUV);
 
     float k = mean(color_a);
 

default/frag8.glsl

@@ -2,7 +2,7 @@
 
 // MFX
 // ------------
-// IN: 9 (A+B)
+// IN: 11 (A+B)
 // IN: 0 (OUT)
 // OUT: 0 (OUT)
 
@@ -11,7 +11,7 @@ out vec4 fragColor;
 
 #include inc_fx.glsl
 
-uniform sampler2D iTex9;
+uniform sampler2D iTex11;
 uniform sampler2D iTex0;
 uniform int iSeed8;
 uniform vec3 iMidi2_3[7];
@@ -20,7 +20,7 @@ uniform int iDemo;
 uniform int iAutoRand;
 
 void main() {
-    vec4 color = fx_stage(vUV, iTex9, iTex0, iSeed8, iMidi2_3[0], iMidi2_3[1].xy, iMidi2_3[2], iMidi2_3[3].xy, iMidi2_3[4], iMidi2_3[5].xy, iMidi2_3[6]);
+    vec4 color = fx_stage(vUV, iTex11, iTex0, iSeed8, iMidi2_3[0], iMidi2_3[1].xy, iMidi2_3[2], iMidi2_3[3].xy, iMidi2_3[4], iMidi2_3[5].xy, iMidi2_3[6]);
 
     if (iDemo < 1 && iAutoRand < 1) {
         color = mix(color, vec4(0), iMidi3_1[0].y);

src/forge.c

@@ -68,6 +68,7 @@ static void init_context(const Parameters *params) {
   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));
 }
 
 static void free_context() { shared_close_context(context); }

src/shaders.c

@@ -88,8 +88,10 @@ static void rebind_textures(const ShaderProgram *program) {
 
 #ifdef VIDEO_IN
 static void link_input_to_texture(ShaderProgram *program, VideoCapture *input,
-                                  unsigned int texture_index) {
+                                  unsigned int texture_index, bool swap) {
-  input->dma_image = EGL_NO_IMAGE_KHR;
+  EGLImageKHR dma_image;
+
+  dma_image = EGL_NO_IMAGE_KHR;
 
   // https://registry.khronos.org/EGL/extensions/EXT/EGL_EXT_image_dma_buf_import.txt
   const EGLint attrib_list[] = {EGL_WIDTH,
@@ -99,18 +101,23 @@ static void link_input_to_texture(ShaderProgram *program, VideoCapture *input,
                                 EGL_LINUX_DRM_FOURCC_EXT,
                                 input->pixelformat,
                                 EGL_DMA_BUF_PLANE0_FD_EXT,
-                                input->exp_fd,
+                                swap ? input->exp_fd_swap : input->exp_fd,
                                 EGL_DMA_BUF_PLANE0_OFFSET_EXT,
                                 0,
                                 EGL_DMA_BUF_PLANE0_PITCH_EXT,
                                 input->bytesperline,
                                 EGL_NONE};
 
-  input->dma_image =
+  dma_image = eglCreateImageKHR(program->egl_display, EGL_NO_CONTEXT,
-      eglCreateImageKHR(program->egl_display, EGL_NO_CONTEXT,
+                                EGL_LINUX_DMA_BUF_EXT, NULL, attrib_list);
-                        EGL_LINUX_DMA_BUF_EXT, NULL, attrib_list);
 
-  if (input->dma_image == EGL_NO_IMAGE_KHR) {
+  if (swap) {
+    input->dma_image_swap = dma_image;
+  } else {
+    input->dma_image = dma_image;
+  }
+
+  if (dma_image == EGL_NO_IMAGE_KHR) {
     log_error("(%s) eglCreateImageKHR failed %04x", input->name, eglGetError());
     return;
   }
@@ -137,7 +144,12 @@ static void init_input(ShaderProgram *program, const ConfigFile *config,
     if (i < inputs->length && !inputs->values[i].error) {
       snprintf(name, STR_LEN, "IN_%d_OUT", i + 1);
       tex_i = config_file_get_int(config, name, 0);
-      link_input_to_texture(program, &inputs->values[i], tex_i);
+      link_input_to_texture(program, &inputs->values[i], tex_i, 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);
+        link_input_to_texture(program, &inputs->values[i], tex_i, true);
+      }
     } else {
       log_warn("Cannot link input %d", i + 1);
     }
@@ -321,6 +333,13 @@ static void 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);
@@ -491,6 +510,8 @@ 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);
   }
 
   // set seeds uniforms
@@ -673,5 +694,8 @@ void shaders_free_input(const ShaderProgram *program,
   if (!input->error && input->dma_image != EGL_NO_IMAGE_KHR) {
     eglDestroyImageKHR(program->egl_display, input->dma_image);
   }
+  if (!input->error && input->dma_image_swap != EGL_NO_IMAGE_KHR) {
+    eglDestroyImageKHR(program->egl_display, input->dma_image_swap);
+  }
 #endif /* VIDEO_IN */
 }

src/types.h

@@ -104,6 +104,7 @@ 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];
@@ -137,15 +138,19 @@ typedef struct ShaderProgram {
 typedef struct VideoCapture {
   char name[STR_LEN];
   bool error;
+  bool with_swap;
   int fd;
   int exp_fd;
+  int exp_fd_swap;
   unsigned int width;
   unsigned int height;
   unsigned int pixelformat;
   unsigned int bytesperline;
 #ifdef VIDEO_IN
   struct v4l2_buffer buf;
+  struct v4l2_buffer buf_swap;
   EGLImageKHR dma_image;
+  EGLImageKHR dma_image_swap;
 #endif /* VIDEO_IN */
 } VideoCapture;
 
@@ -190,6 +195,7 @@ typedef struct SharedContext {
   unsigned int fps;
   unsigned int input_formats[MAX_VIDEO];
   unsigned int input_fps[MAX_VIDEO];
+  bool input_swap[MAX_VIDEO];
   bool stop;
 } SharedContext;
 

src/video.c

@@ -75,7 +75,6 @@ static void open_device(VideoCapture *video_capture, const char *name) {
   strlcpy(video_capture->name, name, STR_LEN);
   video_capture->error = false;
   video_capture->fd = -1;
-  video_capture->exp_fd = -1;
 
   video_capture->fd = open(name, O_RDWR | O_NONBLOCK);
   if (video_capture->fd == -1) {
@@ -201,7 +200,7 @@ static bool request_buffers(VideoCapture *video_capture) {
 
   reqbuf.type = buf_type;
   reqbuf.memory = V4L2_MEMORY_MMAP;
-  reqbuf.count = 1;
+  reqbuf.count = 2;
 
   if (ioctl(video_capture->fd, VIDIOC_REQBUFS, &reqbuf) == -1) {
     ioctl_error(video_capture, "VIDIOC_REQBUFS",
@@ -211,18 +210,21 @@ 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;
+
   return true;
 }
 
-static bool export_buffer(VideoCapture *video_capture) {
+static bool export_buffer(VideoCapture *video_capture, int *fd,
+                          unsigned int index) {
   struct v4l2_exportbuffer expbuf;
 
-  video_capture->exp_fd = -1;
+  *fd = -1;
 
   memset(&expbuf, 0, sizeof(expbuf));
 
   expbuf.type = buf_type;
-  expbuf.index = 0;
+  expbuf.index = index;
   expbuf.flags = O_RDONLY;
 
   if (ioctl(video_capture->fd, VIDIOC_EXPBUF, &expbuf) == -1) {
@@ -232,11 +234,24 @@ static bool export_buffer(VideoCapture *video_capture) {
     return false;
   }
 
-  video_capture->exp_fd = expbuf.fd;
+  *fd = expbuf.fd;
 
   return true;
 }
 
+static bool export_buffers(VideoCapture *video_capture) {
+  bool result;
+
+  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);
+  }
+
+  return result;
+}
+
 static bool open_stream(VideoCapture *video_capture) {
   if (ioctl(video_capture->fd, VIDIOC_STREAMON, &buf_type) == -1) {
     ioctl_error(
@@ -248,30 +263,47 @@ static bool open_stream(VideoCapture *video_capture) {
   return true;
 }
 
-static void create_image_buffer(VideoCapture *video_capture) {
+static void create_image_buffer(const VideoCapture *video_capture,
-  memset(&video_capture->buf, 0, sizeof(video_capture->buf));
+                                struct v4l2_buffer *buf, unsigned int index) {
+  memset(buf, 0, sizeof(*buf));
 
-  video_capture->buf.type = buf_type;
+  buf->type = buf_type;
-  video_capture->buf.memory = V4L2_MEMORY_MMAP;
+  buf->memory = V4L2_MEMORY_MMAP;
-  video_capture->buf.index = 0;
+  buf->index = index;
 
-  ioctl(video_capture->fd, VIDIOC_PREPARE_BUF);
+  ioctl(video_capture->fd, VIDIOC_QBUF, buf);
+}
 
-  ioctl(video_capture->fd, VIDIOC_QBUF, &video_capture->buf);
+static void create_image_buffers(VideoCapture *video_capture) {
+  create_image_buffer(video_capture, &video_capture->buf, 0);
+
+  if (video_capture->with_swap) {
+    create_image_buffer(video_capture, &video_capture->buf_swap, 1);
+  }
 }
 
 static void close_stream(const VideoCapture *video_capture) {
   ioctl(video_capture->fd, VIDIOC_STREAMOFF, &buf_type);
 }
 
-static bool read_video(VideoCapture *video_capture) {
+static unsigned int read_video(const VideoCapture *video_capture) {
+  int result;
+
+  result = 0;
+
   if (ioctl(video_capture->fd, VIDIOC_DQBUF, &video_capture->buf) != -1) {
     ioctl(video_capture->fd, VIDIOC_QBUF, &video_capture->buf);
 
-    return true;
+    result = 1;
+  } else if (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;
   }
 
-  return false;
+  return result;
 }
 
 void video_init(VideoCapture *video_capture, const char *name,
@@ -298,7 +330,7 @@ void video_init(VideoCapture *video_capture, const char *name,
     return;
   }
 
-  if (!export_buffer(video_capture)) {
+  if (!export_buffers(video_capture)) {
     return;
   }
 
@@ -306,7 +338,7 @@ void video_init(VideoCapture *video_capture, const char *name,
     return;
   }
 
-  create_image_buffer(video_capture);
+  create_image_buffers(video_capture);
 }
 
 bool video_background_read(VideoCapture *video_capture, SharedContext *context,
@@ -314,6 +346,7 @@ bool video_background_read(VideoCapture *video_capture, SharedContext *context,
   pid_t pid;
   Timer timer;
   double fps;
+  unsigned int video_result;
 
   pid = fork();
   if (pid < 0) {
@@ -328,7 +361,8 @@ bool video_background_read(VideoCapture *video_capture, SharedContext *context,
   timer_init(&timer, 30);
 
   while (!context->stop) {
-    if (read_video(video_capture) && timer_inc(&timer)) {
+    video_result = read_video(video_capture);
+    if (video_result > 0 && timer_inc(&timer)) {
       fps = timer_reset(&timer);
 
       context->input_fps[input_index] = (unsigned int)round(fps);
@@ -336,6 +370,9 @@ bool video_background_read(VideoCapture *video_capture, SharedContext *context,
         log_trace("(%s) %.2ffps", video_capture->name, fps);
       }
     }
+    if (video_result > 0) {
+      context->input_swap[input_index] = video_result == 2;
+    }
   }
   if (context->stop) {
     log_info("(%s) background acquisition stopped by main thread (pid: %d)",
@@ -355,6 +392,9 @@ void video_free(const VideoCapture *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);
+  }
   if (video_capture->fd != -1) {
     close(video_capture->fd);
   }