add debug msg

cgo/ffmpeg/ffmpeg.c

@@ -17,7 +17,7 @@ int decode(AVCodecContext *avctx, AVFrame *frame, uint8_t *data, int size, int *
     *got_frame = 0;
     
 	printf("avctx: %p\n", avctx);
-	printf("avctx->internal: %p\n", avctx->internal);
+	printf("avctx->internal: %p->%p\n", avctx, avctx->internal);
 
     ret = avcodec_send_packet(avctx, &pkt);