// ranges: ranges in seconds
sS ffmpeg_makeSpliceFilter(L<DoubleRange> ranges) {
  new LS out;
  int i = 0;
  fOr (DoubleRange r : ranges) {
    int lbl = ++i;
    S start = ffmpeg_formatSeconds(r.start);
    S end = ffmpeg_formatSeconds(r.end);
    out.add("[0:v]trim=start=" + start + ":end=" + end + ",setpts=PTS-STARTPTS[v" + lbl + "]");
    out.add("[0:a]atrim=start=" + start + ":end=" + end + ",asetpts=PTS-STARTPTS[a" + lbl + "]");
  }
  S concat = "concat=n=" + l(ranges);
  out.add(joinMap(iota(i), j -> "[v" + j + "]") + concat + "[outv]");
  out.add(joinMap(iota(i), j -> "[a" + j + "]") + + concat + ":v=0:a=1[outa]");
  ret joinWithSemicolon(out);
}