This brief tutorial will provide a general overview on how to generate .vtt subtitle files from digital video files, such as .mp4, using Microsoft Stream. It does not not cover the Microsoft Stream application in detail, the .vtt specification, or the trouble shooting video codecs.
You might have found that Pomona College now has the Microsoft 365 Office Suite available . There are many new tools available and one of those tools is a video streaming application called Microsoft Stream. While Streams main function is to share, store, and deliver video content it also has the ability to automatically generate subtitles in the .vtt format. Explained another way, you are able to upload a video file, such as an .mp4, and Stream will use voice recognition technologies to output a text transcript of the video. That’s quite impressive!
Your output will be a .vtt file which is a specially formatted file that will have lines of text, the spoken words, along with the time that it takes place. Please see below for a link which details the .vtt format.
Now let’s do this, follow the steps below! Following the steps will be a discussion about the realities of this technology and some tips, tricks, tools and list of links.
First, find the Microsoft Stream application. You might find it in the drop down menu that is in your Office 365 web Outlook. You can also try this url: https://www.office.com/ . You may have to “Search all of your apps”.
Second, When you are in Stream you will see “Upload” in a few places. To upload a video, drag and drop it. When you drag and drop you will see some settings that are available, make sure that the “Autogenerate a caption file” has been checked.
Third, the file will usually upload rather quickly. However, autogenerating the .vtt file can take some time. Here is our experience, sometimes it is 5 minutes and sometimes it is 90 minutes for a 120 minute film. No reason, that is just the way it is, so act and plan accordingly.
Next, so you want to check to see if your file is done? To find out goto a listing of your videos and click on the “pencil” icon, that will bing up a page that will allow download of the .vtt subtitle file.
Finally, lets download the file. Just save it like you would any file. Or, you can just leave it there and it can be used with Microsoft Stream.
Realities of this technology, tips and tricks, and some useful tools.
Auto-captioning is not perfect and you should not expect it to be. Some video files work better than others. Here are some things that we have found not to caption well in English.
Musicals do not auto-caption well. Bollywood movies that are in English (or dubbed) do not caption well due to the unique accents. If you have an environment where there is a lot of background noise, like a big noisy crowd at a sporting event, this noise will often drown out the voices that need to be captioned. Finally, any file or media that has poor audio quality does not do well. Overall, a captioning success rate of 90% is generally tolerable. If you need 100% there is a way to modify the .vtt and we will cover that soon.
As of the writing of this article Microsoft Stream also can do Spanish. That means, Spanish audio in then Spanish .vtt text out. Here at Instructional Technology we have not experimented with the Spanish language captioning. There is no option for translation from English to Spanish or Spanish to English, that’s anther tool. We also don’t think language support would dynamically switch. If it does let us know.
What Video Formats Work?
We have found that most everything works and we did chuck some problematic formats at it like FLV and AVIs with H263 codecs. It all worked. If you have something that Stream balks at just transcode it to another format using a tool like Handbrake (see link below) to transform the video to a more common format.
What do I do with the .vtt file and how can I edit it?
You can use Stream to show your videos and Stream will use the .vtt file and show captions in their player. You can search and edit the transcript within Stream itself. Then download the improved file. You can fix those errors and make the transcript 100% accurate.
Additionally you can also download the .vtt file and use it somewhere else like on another web site, as a text transcript, play on the VLC player (see link below), or to add subtitles to a DVD. You will notice that the .vtt file is not easily opened with notepad or a general text editor. To edit it you will want to use a tool like Jubbler (see link below) which will allow editing. You can also use Jubbler to translate the file to other formats. Finally, please note that the textual output that is generated from video files will often take a good amount of manipulation for the text to look like it is from a book or that it reads like one.
Some Links to Software Mentioned Above
Jubbler Subtitle Editor: http://jubler.org/
Handbrake Video Transcoder: https://handbrake.fr/