avisynth: fix setting stream timebase

Stream timebase should be set using avpriv_set_pts_info, otherwise
avctx->pkt_timebase is not correct.

This should fix ticket #4766.

Patch is only compile tested.
Signed-off-by: Marton Balint <cus@passwd.hu>
Reviewed-by: Stephen Hutchinson <qyot27@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/avisynth.c

@@ -237,13 +237,12 @@ static int avisynth_create_stream_video(AVFormatContext *s, AVStream *st)
     st->codec->width      = avs->vi->width;
     st->codec->height     = avs->vi->height;
 
-    st->time_base         = (AVRational) { avs->vi->fps_denominator,
-                                           avs->vi->fps_numerator };
     st->avg_frame_rate    = (AVRational) { avs->vi->fps_numerator,
                                            avs->vi->fps_denominator };
     st->start_time        = 0;
     st->duration          = avs->vi->num_frames;
     st->nb_frames         = avs->vi->num_frames;
+    avpriv_set_pts_info(st, 32, avs->vi->fps_denominator, avs->vi->fps_numerator);
 
     switch (avs->vi->pixel_type) {
 #ifdef USING_AVISYNTH
@@ -311,9 +310,8 @@ static int avisynth_create_stream_audio(AVFormatContext *s, AVStream *st)
     st->codec->codec_type  = AVMEDIA_TYPE_AUDIO;
     st->codec->sample_rate = avs->vi->audio_samples_per_second;
     st->codec->channels    = avs->vi->nchannels;
-    st->time_base          = (AVRational) { 1,
-                                            avs->vi->audio_samples_per_second };
     st->duration           = avs->vi->num_audio_samples;
+    avpriv_set_pts_info(st, 64, 1, avs->vi->audio_samples_per_second);
 
     switch (avs->vi->sample_type) {
     case AVS_SAMPLE_INT8: