diff --git a/devices/video/atirage.cpp b/devices/video/atirage.cpp
index 89d2891..b3953a0 100644
--- a/devices/video/atirage.cpp
+++ b/devices/video/atirage.cpp
@@ -525,6 +525,11 @@ void ATIRage::crtc_enable() {
 
         this->refresh_rate = pixel_clock / hori_total / vert_total;
 
+        // specify framebuffer converter (hardcoded for now)
+        this->convert_fb_cb = [this](uint8_t *dst_buf, int dst_pitch) {
+            this->convert_frame_8bpp(dst_buf, dst_pitch);
+        };
+
         LOG_F(INFO, "ATI Rage: primary CRT controller enabled:");
         LOG_F(INFO, "Video mode: %s",
              (this->mm_regs[ATI_CRTC_GEN_CNTL+3] & 1) ? "extended" : "VGA");
diff --git a/devices/video/videoctrl.cpp b/devices/video/videoctrl.cpp
index 0c78446..d8db848 100644
--- a/devices/video/videoctrl.cpp
+++ b/devices/video/videoctrl.cpp
@@ -28,17 +28,20 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #include <chrono>
 #include <cinttypes>
 
-VideoCtrlBase::VideoCtrlBase()
+VideoCtrlBase::VideoCtrlBase(int width, int height)
 {
     LOG_F(INFO, "Create display window...");
 
+    this->active_width  = width;
+    this->active_height = height;
+
     // Create display window
     this->display_wnd = SDL_CreateWindow(
         "DingusPPC Display",
         SDL_WINDOWPOS_UNDEFINED,
         SDL_WINDOWPOS_UNDEFINED,
-        640,
-        480,
+        this->active_width,
+        this->active_height,
         SDL_WINDOW_OPENGL
     );
 
@@ -98,9 +101,8 @@ void VideoCtrlBase::update_screen()
 
     SDL_LockTexture(this->disp_texture, NULL, (void **)&dst_buf, &dst_pitch);
 
-    // call texture update method (hardcoded for now)
-    // TODO: convert it to a callback
-    this->convert_frame_8bpp(dst_buf, dst_pitch);
+    // texture update callback to get ARGB data from guest framebuffer
+    this->convert_fb_cb(dst_buf, dst_pitch);
 
     SDL_UnlockTexture(this->disp_texture);
     SDL_RenderClear(this->renderer);
@@ -121,6 +123,11 @@ void VideoCtrlBase::update_screen()
     SDL_Delay(15);
 }
 
+void VideoCtrlBase::convert_frame_1bpp(uint8_t *dst_buf, int dst_pitch)
+{
+    // TODO: implement me!
+}
+
 void VideoCtrlBase::convert_frame_8bpp(uint8_t *dst_buf, int dst_pitch)
 {
     uint8_t *src_buf, *src_row, *dst_row, pix;
diff --git a/devices/video/videoctrl.h b/devices/video/videoctrl.h
index 8c8804b..66aa560 100644
--- a/devices/video/videoctrl.h
+++ b/devices/video/videoctrl.h
@@ -27,15 +27,18 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 #include <SDL.h>
 
 #include <cinttypes>
+#include <functional>
 
 class VideoCtrlBase {
 public:
-    VideoCtrlBase();
+    VideoCtrlBase(int width = 640, int height = 480);
     ~VideoCtrlBase();
 
     void update_screen(void);
 
-    void convert_frame_8bpp(uint8_t *dst_buf, int dst_pitch);
+    // converters for various framebuffer pixel depths
+    virtual void convert_frame_1bpp(uint8_t *dst_buf, int dst_pitch);
+    virtual void convert_frame_8bpp(uint8_t *dst_buf, int dst_pitch);
 
 protected:
     /* CRT controller parameters */
@@ -51,6 +54,8 @@ protected:
     uint8_t*    fb_ptr;
     int         fb_pitch;
 
+    std::function<void(uint8_t *dst_buf, int dst_pitch)> convert_fb_cb;
+
 private:
     SDL_Window      *display_wnd;
     SDL_Renderer    *renderer;