Why are subtitles sometimes delayed or out of sync?

For programmes which are pre-recorded, we create the subtitles in advance. A technician uses the audio and picture to sync them with what鈥檚 happening on screen.听 For a programme broadcast live, (like the News), subtitles will be generated as it is broadcast, which is a complex and problematic process. This means you鈥檒l often notice a delay when watching live programmes.