Parsing and converting TED Talks JSON subtitles

This question is related to this other question @ SuperUser.

I want to download the TED Talks and the respective subtitles for offline viewing, for instance lets take this short talk by Richard St. John, the high-resolution video download URL is the following:

http://www.ted.com/talks/download/video/5118/talk/70

And the respective JSON encoded english subtitles can be downloaded at:

http://www.ted.com/talks/subtitles/id/70/lang/eng

Here is an except from the beginning of actual subtitle:

{
  "captions": [{
        "content": "This is really a two hour presentation I give to high school students,",
        "startTime": 0,
        "duration": 3000,
        "startOfParagraph": false
      }, {
        "content": "cut down to three minutes.",
        "startTime": 3000,
        "duration": 1000,
        "startOfParagraph": false
      }, {
        "content": "And it all started one day on a plane, on my way to TED,",
        "startTime": 4000,
        "duration": 3000,
        "startOfParagraph": false
      }, {
        "content": "seven years ago."

And from the end of the subtitle:

{
  "content": "Or failing that, do the eight things -- and trust me,",
  &quo