fftools/ffmpeg_dec: pass input timebase through DecoderOpts

Do not read it from AVStream directly.

This is a step towards decoupling Decoder and InputStream.

fftools/ffmpeg.h

@@ -298,6 +298,8 @@ typedef struct DecoderOpts {
     char                       *hwaccel_device;
     enum AVPixelFormat          hwaccel_output_format;
 
+    AVRational                  time_base;
+
     // Either forced (when DECODER_FLAG_FRAMERATE_FORCED is set) or
     // estimated (otherwise) video framerate.
     AVRational                  framerate;

fftools/ffmpeg_dec.c

@@ -998,10 +998,7 @@ int dec_open(InputStream *ist, Scheduler *sch, unsigned sch_idx,
 
     dp->dec_ctx->opaque                = dp;
     dp->dec_ctx->get_format            = get_format;
-
-    /* Useful for subtitles retiming by lavf (FIXME), skipping samples in
-     * audio, and video decoders such as cuvid or mediacodec */
-    dp->dec_ctx->pkt_timebase = ist->st->time_base;
+    dp->dec_ctx->pkt_timebase          = o->time_base;
 
     if (!av_dict_get(*dec_opts, "threads", NULL, 0))
         av_dict_set(dec_opts, "threads", "auto", 0);

fftools/ffmpeg_demux.c

@@ -1152,6 +1152,8 @@ static int ist_add(const OptionsContext *o, Demuxer *d, AVStream *st)
     ds->first_dts   = AV_NOPTS_VALUE;
     ds->next_dts    = AV_NOPTS_VALUE;
 
+    ds->dec_opts.time_base = st->time_base;
+
     ds->ts_scale = 1.0;
     MATCH_PER_STREAM_OPT(ts_scale, dbl, ds->ts_scale, ic, st);