How to Add Subtitles to TV Broadcast and Why it Matters
November 12, 2020
Subtitles, or closed captions, can play a decisive role for many viewers of television programs. Without subtitles, programs will not be watched by the hearing impaired or those who do not know the main language of the TV program and the broadcaster will lose the viewers. Besides such obvious functions, subtitles play an important role in analytics.
There are laws and regulations in different countries that require a broadcaster to add subtitles to their programs. This applies to linear, satellite, and cable broadcasting. However, in IPTV, these requirements are not always met since the process of adding subtitles to a video stream can in some cases be complicated - it all depends on the standards and video transmission protocols used.
Closed Captions vs Open Captions
Closed captions in the video stream go in the form of text, where one letter is considered to be 1 byte. There is also a DVB standard, in which subtitles are transmitted as images. Accordingly, the text in them is not edited, and it is also impossible to quickly convert them to another format. For IPTV, the WebVTT format is used. Subtitles are sent as text data but already formatted with the font set. Solutions that would allow converting subtitles from DVB into a format suitable for transmission in an IP environment did not exist for a long time. You can burn subtitles in using transcoding to a video stream, however, this turns closed captions into open captions, which cannot be removed from the screen. Of course, this is not very convenient and it causes losses in the quality of the video stream.
At the end of last summer, Flussonic released a solution for converting subtitles from one format to another using OCR. In real time, OCR can convert text from a picture to an HLS text data format. There is also an additional option that allows for automatic translation with minimal delay.
In Canada and the United States, there are regulations that require subtitles to appear on most programs provided by a broadcaster. US operator Southern Fibernet used our subtitling solution as a critical precondition for launching their IPTV service. Now the operator complies with the requirements of the US regulator FCC and can provide its customers with subtitles on demand.
In European countries and Latin American countries, the possibility of automatic translation of subtitles into different languages is especially relevant. For example, programs in Spanish are very popular in Portugal, but until recently, local operators also had the problem of converting DVB subtitles to WebVTT. We helped Latin American operator Glidertek to implement the conversion solution.
Today, the ability to convert subtitles using OCR in real time is a rarity on the market, however, it is a very important detail that plays a big role for broadcasters and becomes a decisive factor for viewers when choosing a telecom operator.