This was the original standard for analog TV where captions were "hidden" in line 21 of the vertical blanking interval of the video signal. While robust, these captions are not customizable by the viewer in terms of font or color.
This is the newer digital standard. Unlike Line 21, it allows viewers to change the appearance of captions, such as text size and background transparency. subtitle 21
Widely reviewed as the "best free subtitling tool," it has recently added features like AI audio-to-text (using Whisper or Vosk) and the ability to burn-in subtitles directly into the video. This was the original standard for analog TV
Keep text concise and on-screen long enough for a person to read comfortably. Unlike Line 21, it allows viewers to change
Interestingly, some early Blu-rays still carry "old-fashioned" Line 21 captions. However, these are often only visible if using a composite (analog) output rather than HDMI. Modern Tools for Subtitle Management
If you are looking to create or review subtitles today, several high-rated tools offer modern alternatives to legacy captioning:
