How the YouTube Auto Captioning algorithm works

YouTube gives us the ability to generate automatic subtitles for our videos in ten different languages. By the beginning of this year, they reported that since 2009 they had subtitled more than one billion videos. But how do they do it?

The short answer: Machine Learning

The long answer:

To generate automatic captions, YouTube combines Google's automated speech recognition technology, the same device used by Google Home to understand your orders, with its own subtitling system.

The algorithm recognizes the words in the video and converts them to text, for this it uses models of Gaussian mixes and deep neural networks. It also synchronizes the text with the video to determine when each line should appear and disappear.

But the magic does not end there. Machine learning is a series of algorithms that make your application artificially intelligent. In the case of YouTube's automatic subtitling process, this means that the algorithm is learning all the time.

Using manual transcripts uploaded by users to the platform, or corrections to automatic captions, YouTube continually refines its transcription system and decreases the percentage of errors in captioned videos.

How do I enable automatic captions for my video on YouTube?

Whether you want to make your videos accessible to the hearing impaired, translate your content to other languages, or even improve the positioning of your channel in search engines, turning subtitles on your videos is an excellent practice.

The good news is you do not have to take any additional steps. If there are automatic captions available for your video, they will be posted immediately, and your subscribers can activate them by clicking the "CC" button in the lower right corner of the player. Keep in mind that there is a processing time and subtitles may not be available immediately after uploading a video.

The bad news is that there will not always be subtitles available for your video. This may be because the audio quality does not allow the algorithm to recognize the words, or the video is too long, or YouTube does not support the language within those videos.

Whatever the reason, when automatic captions are not generated, you still have the option of uploading your own transcript and letting the algorithm synchronize it with your audio, or create your own captions from scratch using YouTube's own platform. But that's the theme for another post. 😉