reduce ffmpeg warnings part 2 , thx DboxOldie

- part 1 see here ff91a9a


Origin commit data
------------------
Commit: 3badd9110a
Author: Frankenstone <dampf_acc@online.de>
Date: 2019-03-01 (Fri, 01 Mar 2019)

src/driver/audiodec/ffmpegdec.cpp

@@ -405,7 +405,11 @@ CBaseDec::RetCode CFfmpegDec::Decoder(FILE *_in, int /*OutputFd*/, State* state,
 					fprintf(stderr,"%s: PCM write error (%s).\n", ProgName, strerror(errno));
 					Status=WRITE_ERR;
 				}
+#if (LIBAVUTIL_VERSION_MAJOR < 54)
 				pts = av_frame_get_best_effort_timestamp(frame);
+#else
+				pts = frame->best_effort_timestamp;
+#endif
 				if (!start_pts)
 					start_pts = pts;
 			}