avformat/movenchint: Fix movhinting with ff_rtp_chain_mux_open() from abb810db03

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

libavformat/movenchint.c

@@ -33,6 +33,7 @@ int ff_mov_init_hinting(AVFormatContext *s, int index, int src_index)
     MOVTrack *src_track = &mov->tracks[src_index];
     AVStream *src_st    = s->streams[src_index];
     int ret = AVERROR(ENOMEM);
+    AVRational src_timebase = src_st->time_base;
 
     track->tag = MKTAG('r','t','p',' ');
     track->src_track = src_index;
@@ -48,6 +49,8 @@ int ff_mov_init_hinting(AVFormatContext *s, int index, int src_index)
     if (ret < 0)
         goto fail;
 
+    src_st->time_base = src_timebase; // prevent ff_rtp_chain_mux_open() from corrupting the timebase
+
     /* Copy the RTP AVStream timebase back to the hint AVStream */
     track->timescale = track->rtp_ctx->streams[0]->time_base.den;