avdevice/lavfi: do not rescale AV_NOPTS_VALUE in lavfi_read_packet()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 913685f5)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavdevice/lavfi.c

@@ -343,7 +343,7 @@ static int lavfi_read_packet(AVFormatContext *avctx, AVPacket *pkt)
             continue;
         } else if (ret < 0)
             return ret;
-        d = av_rescale_q(frame->pts, tb, AV_TIME_BASE_Q);
+        d = av_rescale_q_rnd(frame->pts, tb, AV_TIME_BASE_Q, AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
         av_dlog(avctx, "sink_idx:%d time:%f\n", i, d);
         av_frame_unref(frame);