avfilter/vf_framerate: do not calculate scene change score multiple times for the same frame

This speeds up the filter, and also fixes scene change detection score which is
reduced based on the difference of the current MAFD to the preivous MAFD.
Obviously if we compare two frames twice, the difference will be 0...
Signed-off-by: Marton Balint <cus@passwd.hu>

libavfilter/vf_framerate.c

@@ -71,6 +71,7 @@ typedef struct FrameRateContext {
 
     AVFrame *srce[N_SRCE];              ///< buffered source frames
     int64_t srce_pts_dest[N_SRCE];      ///< pts for source frames scaled to output timebase
+    double srce_score[N_SRCE];          ///< scene change score compared to the next srce frame
     int64_t pts;                        ///< pts of frame we are working on
 
     int max;
@@ -113,9 +114,11 @@ static void next_source(AVFilterContext *ctx)
     for (i = s->last; i > s->frst; i--) {
         ff_dlog(ctx, "next_source() copy %d to %d\n", i - 1, i);
         s->srce[i] = s->srce[i - 1];
+        s->srce_score[i] = s->srce_score[i - 1];
     }
     ff_dlog(ctx, "next_source() make %d null\n", s->frst);
     s->srce[s->frst] = NULL;
+    s->srce_score[s->frst] = -1.0;
 }
 
 static av_always_inline int64_t sad_8x8_16(const uint16_t *src1, ptrdiff_t stride1,
@@ -171,8 +174,7 @@ static double get_scene_score(AVFilterContext *ctx, AVFrame *crnt, AVFrame *next
 
     ff_dlog(ctx, "get_scene_score()\n");
 
-    if (crnt &&
-        crnt->height == next->height &&
+    if (crnt->height == next->height &&
         crnt->width  == next->width) {
         int64_t sad;
         double mafd, diff;
@@ -304,21 +306,26 @@ static int filter_slice16(AVFilterContext *ctx, void *arg, int job, int nb_jobs)
 }
 
 static int blend_frames(AVFilterContext *ctx, float interpolate,
-                        AVFrame *copy_src1, AVFrame *copy_src2)
+                        int src1, int src2)
 {
     FrameRateContext *s = ctx->priv;
     AVFilterLink *outlink = ctx->outputs[0];
     double interpolate_scene_score = 0;
 
-    if ((s->flags & FRAMERATE_FLAG_SCD) && copy_src2) {
-        interpolate_scene_score = get_scene_score(ctx, copy_src1, copy_src2);
+    if ((s->flags & FRAMERATE_FLAG_SCD) && s->srce[src1] && s->srce[src2]) {
+        int i1 = src1 < src2 ? src1 : src2;
+        int i2 = src1 < src2 ? src2 : src1;
+        if (i2 == i1 + 1 && s->srce_score[i1] >= 0.0)
+            interpolate_scene_score = s->srce_score[i1];
+        else
+            interpolate_scene_score = s->srce_score[i1] = get_scene_score(ctx, s->srce[i1], s->srce[i2]);
         ff_dlog(ctx, "blend_frames() interpolate scene score:%f\n", interpolate_scene_score);
     }
     // decide if the shot-change detection allows us to blend two frames
-    if (interpolate_scene_score < s->scene_score && copy_src2) {
+    if (interpolate_scene_score < s->scene_score && s->srce[src2]) {
         ThreadData td;
-        td.copy_src1 = copy_src1;
-        td.copy_src2 = copy_src2;
+        td.copy_src1 = s->srce[src1];
+        td.copy_src2 = s->srce[src2];
         td.src2_factor = fabsf(interpolate) * (1 << (s->bitdepth - 8));
         td.src1_factor = s->max - td.src2_factor;
 
@@ -340,8 +347,8 @@ static int process_work_frame(AVFilterContext *ctx, int stop)
 {
     FrameRateContext *s = ctx->priv;
     int64_t work_next_pts;
-    AVFrame *copy_src1;
     float interpolate;
+    int src1, src2;
 
     ff_dlog(ctx, "process_work_frame()\n");
 
@@ -385,28 +392,26 @@ static int process_work_frame(AVFilterContext *ctx, int stop)
     // calculate interpolation
     interpolate = ((s->pts - s->srce_pts_dest[s->crnt]) * 256.0 / s->average_srce_pts_dest_delta);
     ff_dlog(ctx, "process_work_frame() interpolate:%f/256\n", interpolate);
-    copy_src1 = s->srce[s->crnt];
+    src1 = s->crnt;
     if (interpolate > s->interp_end) {
         ff_dlog(ctx, "process_work_frame() source is:NEXT\n");
-        copy_src1 = s->srce[s->next];
+        src1 = s->next;
     }
     if (s->srce[s->prev] && interpolate < -s->interp_end) {
         ff_dlog(ctx, "process_work_frame() source is:PREV\n");
-        copy_src1 = s->srce[s->prev];
+        src1 = s->prev;
     }
 
     // decide whether to blend two frames
     if ((interpolate >= s->interp_start && interpolate <= s->interp_end) || (interpolate <= -s->interp_start && interpolate >= -s->interp_end)) {
-        AVFrame *copy_src2;
-
         if (interpolate > 0) {
             ff_dlog(ctx, "process_work_frame() interpolate source is:NEXT\n");
-            copy_src2 = s->srce[s->next];
+            src2 = s->next;
         } else {
             ff_dlog(ctx, "process_work_frame() interpolate source is:PREV\n");
-            copy_src2 = s->srce[s->prev];
+            src2 = s->prev;
         }
-        if (blend_frames(ctx, interpolate, copy_src1, copy_src2))
+        if (blend_frames(ctx, interpolate, src1, src2))
             goto copy_done;
         else
             ff_dlog(ctx, "process_work_frame() CUT - DON'T INTERPOLATE\n");
@@ -414,7 +419,7 @@ static int process_work_frame(AVFilterContext *ctx, int stop)
 
     ff_dlog(ctx, "process_work_frame() COPY to the work frame\n");
     // copy the frame we decided is our base source
-    s->work = av_frame_clone(copy_src1);
+    s->work = av_frame_clone(s->srce[src1]);
     if (!s->work)
         return AVERROR(ENOMEM);
 
@@ -504,6 +509,7 @@ static void set_work_frame_pts(AVFilterContext *ctx)
 static av_cold int init(AVFilterContext *ctx)
 {
     FrameRateContext *s = ctx->priv;
+    int i;
 
     s->dest_frame_num = 0;
 
@@ -513,6 +519,9 @@ static av_cold int init(AVFilterContext *ctx)
     s->next = s->crnt - 1;
     s->prev = s->crnt + 1;
 
+    for (i = 0; i < N_SRCE; i++)
+        s->srce_score[i] = -1.0;
+
     return 0;
 }