cinepak: detect keyframes

Code by DivX, Inc.
Taken from drffmpeg
Author: unknown

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/cinepak.c

@@ -355,6 +355,8 @@ static int cinepak_decode (CinepakContext *s)
     if (num_strips > MAX_STRIPS)
         num_strips = MAX_STRIPS;
 
+    s->frame.key_frame = 0;
+
     for (i=0; i < num_strips; i++) {
         if ((s->data + 12) > eod)
             return -1;
@@ -365,6 +367,9 @@ static int cinepak_decode (CinepakContext *s)
         s->strips[i].y2 = y0 + AV_RB16 (&s->data[8]);
         s->strips[i].x2 = s->avctx->width;
 
+        if (s->strips[i].id == 0x10)
+            s->frame.key_frame = 1;
+
         strip_size = AV_RB24 (&s->data[1]) - 12;
         s->data   += 12;
         strip_size = ((s->data + strip_size) > eod) ? (eod - s->data) : strip_size;