static L<DoubleRange> parseTimestampRanges(S s) {
  new L<DoubleRange> l;
  for (S line : tlft(s)) {
    int i = indexOf(s, '-');
    LS x = trimAll(splitAt_withEmptyLast(line, "-"));
    if (l(x) != 2) continue with print("parseTimestampRanges unknown line: " + line);
    l.add(doubleRange(
      ffmpeg_parseTimestamp(first(x)),
      ffmpeg_parseTimestamp(second(x))));
  }
  ret l;
}