avcodec/mpeg4videodec: Fix integer overflow in num_sprite_warping_points=2 case

Fixes: runtime error: signed integer overflow: 131072 + 2147352576 cannot be represented in type 'int'
Fixes: 2192/clusterfuzz-testcase-minimized-5370387988742144

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mpeg4videodec.c

@@ -284,26 +284,26 @@ static int mpeg4_decode_sprite_trajectory(Mpeg4DecContext *ctx, GetBitContext *g
         ctx->sprite_shift[1]   = 0;
         break;
     case 2:
-        sprite_offset[0][0]    = (sprite_ref[0][0] * (1 << alpha + rho)) +
-                                 (-r * sprite_ref[0][0] + virtual_ref[0][0]) *
-                                 (-vop_ref[0][0]) +
-                                 (r * sprite_ref[0][1] - virtual_ref[0][1]) *
-                                 (-vop_ref[0][1]) + (1 << (alpha + rho - 1));
-        sprite_offset[0][1]    = (sprite_ref[0][1] * (1 << alpha + rho)) +
-                                 (-r * sprite_ref[0][1] + virtual_ref[0][1]) *
-                                 (-vop_ref[0][0]) +
-                                 (-r * sprite_ref[0][0] + virtual_ref[0][0]) *
-                                 (-vop_ref[0][1]) + (1 << (alpha + rho - 1));
-        sprite_offset[1][0]    = ((-r * sprite_ref[0][0] + virtual_ref[0][0]) *
-                                  (-2 * vop_ref[0][0] + 1) +
-                                  (r * sprite_ref[0][1] - virtual_ref[0][1]) *
-                                  (-2 * vop_ref[0][1] + 1) + 2 * w2 * r *
-                                  sprite_ref[0][0] - 16 * w2 + (1 << (alpha + rho + 1)));
-        sprite_offset[1][1]    = ((-r * sprite_ref[0][1] + virtual_ref[0][1]) *
-                                  (-2 * vop_ref[0][0] + 1) +
-                                  (-r * sprite_ref[0][0] + virtual_ref[0][0]) *
-                                  (-2 * vop_ref[0][1] + 1) + 2 * w2 * r *
-                                  sprite_ref[0][1] - 16 * w2 + (1 << (alpha + rho + 1)));
+        sprite_offset[0][0]    = ((int64_t)      sprite_ref[0][0] * (1 << alpha + rho)) +
+                                 ((int64_t) -r * sprite_ref[0][0] + virtual_ref[0][0]) *
+                                 ((int64_t)        -vop_ref[0][0]) +
+                                 ((int64_t)  r * sprite_ref[0][1] - virtual_ref[0][1]) *
+                                 ((int64_t)        -vop_ref[0][1]) + (1 << (alpha + rho - 1));
+        sprite_offset[0][1]    = ((int64_t)      sprite_ref[0][1] * (1 << alpha + rho)) +
+                                 ((int64_t) -r * sprite_ref[0][1] + virtual_ref[0][1]) *
+                                 ((int64_t)        -vop_ref[0][0]) +
+                                 ((int64_t) -r * sprite_ref[0][0] + virtual_ref[0][0]) *
+                                 ((int64_t)        -vop_ref[0][1]) + (1 << (alpha + rho - 1));
+        sprite_offset[1][0]    = (((int64_t)-r * sprite_ref[0][0] + virtual_ref[0][0]) *
+                                  ((int64_t)-2 *    vop_ref[0][0] + 1) +
+                                  ((int64_t) r * sprite_ref[0][1] - virtual_ref[0][1]) *
+                                  ((int64_t)-2 *    vop_ref[0][1] + 1) + 2 * w2 * r *
+                                   (int64_t)     sprite_ref[0][0] - 16 * w2 + (1 << (alpha + rho + 1)));
+        sprite_offset[1][1]    = (((int64_t)-r * sprite_ref[0][1] + virtual_ref[0][1]) *
+                                  ((int64_t)-2 *    vop_ref[0][0] + 1) +
+                                  ((int64_t)-r * sprite_ref[0][0] + virtual_ref[0][0]) *
+                                  ((int64_t)-2 *    vop_ref[0][1] + 1) + 2 * w2 * r *
+                                  (int64_t)      sprite_ref[0][1] - 16 * w2 + (1 << (alpha + rho + 1)));
         s->sprite_delta[0][0] = (-r * sprite_ref[0][0] + virtual_ref[0][0]);
         s->sprite_delta[0][1] = (+r * sprite_ref[0][1] - virtual_ref[0][1]);
         s->sprite_delta[1][0] = (-r * sprite_ref[0][1] + virtual_ref[0][1]);