Make Bink decoder to stop decoding planes after all bits are used.

This prevents crashes during decoding grayscale Bink files like
samples from Impossible Creatures game demo.

Originally committed as revision 21961 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/bink.c

@@ -681,6 +681,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPac
     DECLARE_ALIGNED_16(DCTELEM, block[64]);
     DECLARE_ALIGNED_16(uint8_t, ublock[64]);
     int coordmap[64];
+    int bits_count = pkt->size << 3;
 
     if(c->pic.data[0])
         avctx->release_buffer(avctx, &c->pic);
@@ -690,7 +691,7 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPac
         return -1;
     }
 
-    init_get_bits(&gb, pkt->data, pkt->size*8);
+    init_get_bits(&gb, pkt->data, bits_count);
     if (c->version >= 'i')
         skip_bits_long(&gb, 32);
 
@@ -901,6 +902,8 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPac
         }
         if (get_bits_count(&gb) & 0x1F) //next plane data starts at 32-bit boundary
             skip_bits_long(&gb, 32 - (get_bits_count(&gb) & 0x1F));
+        if (get_bits_count(&gb) >= bits_count)
+            break;
     }
     emms_c();