How exactly are subtitles created for videos?

The demand for subtitles is on the rise. This is down to accessibility requirements but also the fact that providing subtitles in multiple languages allows content creators in multilingual Switzerland to reach a wider national and international audience. But how are subtitles created? And what does the translation process involve?

We all know that we need a source text to start off with. This is the speech to text stage. Traditionally, the words spoken in a video are typed out. This process is called transcription. But we need more than just the spoken text to produce subtitles – and the time codes are the most important information of all. This is because we need to know when each sentence is spoken and how long the subtitles will appear on screen for. Transcription is a skill in itself. If you’ve ever had a go, you’ll know how much time and effort is involved.

illustration subtitles

Prep work by artificial intelligence

It probably won’t come as much of a surprise that transcription is largely automated these days. Here at Apostroph, we use an AI tool called Whisper. The automatic speech recognition system developed by OpenAI (the company behind ChatGPT) offers surprisingly high recognition accuracy. We feed a video file into Whisper, which returns a subtitle file, usually in SRT format. This contains the transcription of the text in the video with the time codes included. So far so good!

Even though we’re pleasantly surprised by its recognition accuracy, Whisper isn’t perfect. Knowing that, we check the accuracy of the source text produced by the system and make sure the subtitles are the right length and the position of the time codes is correct, so that the subtitles are shown at the right time and for the right length of time (spotting). And then we can be happy that the subtitle file is ready for translation.

Translation tools for subtitle files

When you open the file for translation in Word, it’ll look something like this:

Illustration subtitles

Sure, you can read and translate the text in that format. But it could be much better. You see, subtitles are presented more clearly in specialist subtitling software like Aegisub and Subtitle Edit. And you can integrate the corresponding video file so you can check that the subtitles work as you go. Are they shown at the right point in the video? Are they on screen for long enough (at least one second)? Are they the right length? You can translate the subtitles directly in these tools and then save the file under a new name – just like you would if you were working in Word.

You do also have the option of translating subtitle files in Trados Studio. If you install the Studio Subtitling plugin (available from the RWS AppStore), you’ll be shown a video preview of your subtitles as you translate them. There’s also a Subtitling Data tab at the bottom of the window that provides important details like the length of your text.

What’s the process for working on subtitling projects?

  • If we’ve asked you to check a subtitle source file for us, we’ll send you an SRT file and all the details you need. It’s then over to you to edit the subtitles in one of the tools we mentioned before and deliver the updated SRT file, adding _edit to the end of the file name.
  • Subtitle translation projects will usually be sent as a Studio project, which you can work with as normal. You’ll need to download the Studio Subtitling plugin we already mentioned to be able to translate the subtitles. As usual, we expect you to deliver the target file and the SDLXLIFF.
  • For very urgent translation projects, we might ask you to work directly with the source text created by AI or we might provide you with an SRT file that has been generated by AI and then pre-translated using machine translation. If this happens, we ask that you open the transcript/SRT file in your subtitling software or Studio (with the video) and check the quality first of all (make sure the file is linguistically correct, the time codes are right and the standard subtitling guidelines have been followed). You should speak to the project manager if you notice that the spotting is completely wrong or the pre-translation isn’t fit for purpose.

Further information

Special rules apply  to transcription and subtitling projects. You can find our guidelines in the Knowledge Portal on myFREELANCE:

We also ran a training session on this topic in January and looked at Whisper in more detail. You can find the recording here:


All three tools are free. Try them out!

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