Buffer frame to sync with vsync in SDL

src/sdl.c

@@ -33,7 +33,11 @@ static SDL_Texture *bmp;
 
 SDL_mutex *mutex;
 
+int sdlCurrentFrame, sdlNextFrame;
+
 void sdl_init(int width, int height, bool fullscreen) {
+  sdlCurrentFrame = sdlNextFrame = 0;
+
   if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS)) {
     fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
     exit(1);
@@ -65,7 +69,6 @@ void sdl_init(int width, int height, bool fullscreen) {
     exit(1);
   }
 
-
   sdlinput_init();
 }
 
@@ -90,14 +93,16 @@ void sdl_loop() {
         done = true;
       else if (event.type == SDL_USEREVENT) {
         if (event.user.code == SDL_CODE_FRAME) {
-          if (SDL_LockMutex(mutex) == 0) {
+          if (++sdlCurrentFrame <= sdlNextFrame - SDL_BUFFER_FRAMES) {
+            //Skip frame
+          } else if (SDL_LockMutex(mutex) == 0) {
             Uint8** data = ((Uint8**) event.user.data1);
             int* linesize = ((int*) event.user.data2);
             SDL_UpdateYUVTexture(bmp, NULL, data[0], linesize[0], data[1], linesize[1], data[2], linesize[2]);
+            SDL_UnlockMutex(mutex);
             SDL_RenderClear(renderer);
             SDL_RenderCopy(renderer, bmp, NULL, NULL);
             SDL_RenderPresent(renderer);
-            SDL_UnlockMutex(mutex);
           } else
             fprintf(stderr, "Couldn't lock mutex\n");
         }

src/sdl.h

@@ -31,9 +31,12 @@
 
 #define SDL_CODE_FRAME 0
 
+#define SDL_BUFFER_FRAMES 2
+
 void sdl_init(int width, int height, bool fullscreen);
 void sdl_loop();
 
 SDL_mutex *mutex;
+int sdlCurrentFrame, sdlNextFrame;
 
 #endif /* HAVE_SDL */

src/video/ffmpeg.c

@@ -35,7 +35,10 @@
 static AVPacket pkt;
 static AVCodec* decoder;
 static AVCodecContext* decoder_ctx;
-static AVFrame* dec_frame;
+static AVFrame** dec_frames;
+
+static int dec_frames_cnt;
+static int current_frame, next_frame;
 
 enum decoders {SOFTWARE, VDPAU};
 enum decoders decoder_system;
@@ -44,7 +47,7 @@ enum decoders decoder_system;
 
 // This function must be called before
 // any other decoding functions
-int ffmpeg_init(int videoFormat, int width, int height, int perf_lvl, int thread_count) {
+int ffmpeg_init(int videoFormat, int width, int height, int perf_lvl, int buffer_count, int thread_count) {
   // Initialize the avcodec library and register codecs
   av_log_set_level(AV_LOG_QUIET);
   avcodec_register_all();
@@ -114,12 +117,21 @@ int ffmpeg_init(int videoFormat, int width, int height, int perf_lvl, int thread
     return err;
   }
 
-  dec_frame = av_frame_alloc();
-  if (dec_frame == NULL) {
-    printf("Couldn't allocate frame");
+  dec_frames_cnt = buffer_count;
+  dec_frames = malloc(buffer_count * sizeof(AVFrame*));
+  if (dec_frames == NULL) {
+    fprintf(stderr, "Couldn't allocate frames");
     return -1;
   }
 
+  for (int i = 0; i < buffer_count; i++) {
+    dec_frames[i] = av_frame_alloc();
+    if (dec_frames[i] == NULL) {
+      fprintf(stderr, "Couldn't allocate frame");
+      return -1;
+    }
+  }
+
   #ifdef HAVE_VDPAU
   if (decoder_system == VDPAU)
     vdpau_init(decoder_ctx, width, height);
@@ -136,18 +148,20 @@ void ffmpeg_destroy(void) {
     av_free(decoder_ctx);
     decoder_ctx = NULL;
   }
-  if (dec_frame) {
-    av_frame_free(&dec_frame);
-    dec_frame = NULL;
+  if (dec_frames) {
+    for (int i = 0; i < dec_frames_cnt; i++) {
+      if (dec_frames[i])
+        av_frame_free(&dec_frames[i]);
+    }
   }
 }
 
 AVFrame* ffmpeg_get_frame() {
   if (decoder_system == SOFTWARE)
-    return dec_frame;
+    return dec_frames[current_frame];
   #ifdef HAVE_VDPAU
   else if (decoder_system == VDPAU)
-    return vdpau_get_frame(dec_frame);
+    return vdpau_get_frame(dec_frames[current_frame]);
   #endif
 }
 
@@ -162,7 +176,7 @@ int ffmpeg_decode(unsigned char* indata, int inlen) {
 
   while (pkt.size > 0) {
     got_pic = 0;
-    err = avcodec_decode_video2(decoder_ctx, dec_frame, &got_pic, &pkt);
+    err = avcodec_decode_video2(decoder_ctx, dec_frames[next_frame], &got_pic, &pkt);
     if (err < 0) {
       char errorstring[512];
       av_strerror(err, errorstring, sizeof(errorstring));
@@ -176,6 +190,8 @@ int ffmpeg_decode(unsigned char* indata, int inlen) {
   }
   
   if (got_pic) {
+    current_frame = next_frame;
+    next_frame = (current_frame+1) % dec_frames_cnt;
     return 1;
   }
 

src/video/ffmpeg.h

@@ -34,7 +34,7 @@
 // Uses hardware acceleration
 #define HARDWARE_ACCELERATION 0x40
 
-int ffmpeg_init(int videoFormat, int width, int height, int perf_lvl, int thread_count);
+int ffmpeg_init(int videoFormat, int width, int height, int perf_lvl, int buffer_count, int thread_count);
 void ffmpeg_destroy(void);
 
 int ffmpeg_draw_frame(AVFrame *pict);

src/video/sdl.c

@@ -37,7 +37,7 @@ static void sdl_setup(int videoFormat, int width, int height, int redrawRate, vo
   if (drFlags & FORCE_HARDWARE_ACCELERATION)
     avc_flags |= HARDWARE_ACCELERATION;
 
-  if (ffmpeg_init(videoFormat, width, height, avc_flags, 2) < 0) {
+  if (ffmpeg_init(videoFormat, width, height, avc_flags, SDL_BUFFER_FRAMES, 2) < 0) {
     fprintf(stderr, "Couldn't initialize video decoding\n");
     exit(1);
   }
@@ -66,6 +66,7 @@ static int sdl_submit_decode_unit(PDECODE_UNIT decodeUnit) {
     if (SDL_LockMutex(mutex) == 0) {
       int ret = ffmpeg_decode(ffmpeg_buffer, length);
       if (ret == 1) {
+        sdlNextFrame++;
         AVFrame* frame = ffmpeg_get_frame();
 
         SDL_Event event;