add debug msg

cgo/ffmpeg/ffmpeg.c

@@ -16,7 +16,7 @@ int decode(AVCodecContext *avctx, AVFrame *frame, uint8_t *data, int size, int *
 
     *got_frame = 0;
     
-	printf("avctx: %p\n", avctx);
+	printf("avctx: %p, data: %p, size: %d\n", avctx, data, size);
 	printf("avctx->internal: %p->%p\n", avctx, avctx->internal);
 
     ret = avcodec_send_packet(avctx, &pkt);