ffmpeg: Correct inter stream timestamp discontinuities

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

ffmpeg.c

@@ -2942,6 +2942,23 @@ static int process_input(int file_index)
     if (pkt.dts != AV_NOPTS_VALUE)
         pkt.dts *= ist->ts_scale;
 
+    if (pkt.dts != AV_NOPTS_VALUE && ist->next_dts == AV_NOPTS_VALUE && !copy_ts
+        && (is->iformat->flags & AVFMT_TS_DISCONT) && ifile->last_ts != AV_NOPTS_VALUE) {
+        int64_t pkt_dts = av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q);
+        int64_t delta   = pkt_dts - ifile->last_ts;
+        if(delta < -1LL*dts_delta_threshold*AV_TIME_BASE ||
+            (delta > 1LL*dts_delta_threshold*AV_TIME_BASE &&
+                ist->st->codec->codec_type != AVMEDIA_TYPE_SUBTITLE)){
+            ifile->ts_offset -= delta;
+            av_log(NULL, AV_LOG_DEBUG,
+                   "Inter stream timestamp discontinuity %"PRId64", new offset= %"PRId64"\n",
+                   delta, ifile->ts_offset);
+            pkt.dts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
+            if (pkt.pts != AV_NOPTS_VALUE)
+                pkt.pts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
+        }
+    }
+
     if (pkt.dts != AV_NOPTS_VALUE && ist->next_dts != AV_NOPTS_VALUE &&
         !copy_ts) {
         int64_t pkt_dts = av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q);
@@ -2979,6 +2996,9 @@ static int process_input(int file_index)
         }
     }
 
+    if (pkt.dts != AV_NOPTS_VALUE)
+        ifile->last_ts = av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q);
+
     if (debug_ts) {
         av_log(NULL, AV_LOG_INFO, "demuxer+ffmpeg -> ist_index:%d type:%s pkt_pts:%s pkt_pts_time:%s pkt_dts:%s pkt_dts_time:%s off:%s off_time:%s\n",
                ifile->ist_index + pkt.stream_index, av_get_media_type_string(ist->st->codec->codec_type),

ffmpeg.h

@@ -278,6 +278,7 @@ typedef struct InputFile {
     int eagain;           /* true if last read attempt returned EAGAIN */
     int ist_index;        /* index of first stream in input_streams */
     int64_t ts_offset;
+    int64_t last_ts;
     int nb_streams;       /* number of stream that ffmpeg is aware of; may be different
                              from ctx.nb_streams if new streams appear during av_read_frame() */
     int nb_streams_warn;  /* number of streams that the user was warned of */