avformat/wavdec: Fix smv packet interleaving

This strips the relative timestamp "flag" off.

Fixes Ticket2849
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/wavdec.c

@@ -466,8 +466,8 @@ static int wav_read_packet(AVFormatContext *s, AVPacket *pkt)
     if (wav->smv_data_ofs > 0) {
         int64_t audio_dts, video_dts;
 smv_retry:
-        audio_dts = s->streams[0]->cur_dts;
-        video_dts = s->streams[1]->cur_dts;
+        audio_dts = (int32_t)s->streams[0]->cur_dts;
+        video_dts = (int32_t)s->streams[1]->cur_dts;
 
         if (audio_dts != AV_NOPTS_VALUE && video_dts != AV_NOPTS_VALUE) {
             /*We always return a video frame first to get the pixel format first*/