Experiments in writing, by Marjolein Hoekstra @OneNoteC

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Creating Office Mix Closed Captions

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Ever since the Microsoft Office Mix team announced that their PowerPoint 2013 add-in was now supporting closed captions, I’ve been wanting to try it out. I’m a very strong proponent of producing videos #WithCaptions and I thank the Office Mix Team wholeheartedly for acknowledging the importance of offering this courteous feature.

When I talked to Microsoft’s Preston Peine about his #OneNoteWithPreston series, he challenged me to go for it with his most recent Office Mix presentation “Class Notebooks with Shared Computers“. It so happens that Preston – through the Mix privacy settings – made the .PPTX source of his Office Mix presentation available for remixing, so I could just download that .PPTX file and open it in my own copy of PowerPoint 2013.

For those with little time on their hands, here’s the end result of my efforts:

Preston Peine’s Mix presentation:

Class Notebooks with Shared Computers #WithCaptions


Class Notebooks with Shared Computers - with captions

Class Notebooks with Shared Computers – with captions


Why closed captions?

There are multiple reasons to caption a video. I can think of these reasons:

  • as a courtesy to the hearing-impaired
  • to support non-native speakers
  • to promote better comprehension and retention
  • for SEO motives – captions are indexed by search engines

There’s an upcoming movement that promotes video captioning. It uses the #WithCaptions hashtag on social media. For more inspiration, watch the video in this recent Upworthy article Pretty Much a No-Brainer.

The remainder of this post contains notes about my first experiences creating closed captions for Office Mix. I followed the development team’s excellent instructions for closed captions on the Office Mix Uservoice Knowledge Base, basically boiling down to a few steps. If you want to follow along with the steps in this post, make sure you have performed these three:

  1. download a copy of the original .PPTX of an Office Mix and open it in PowerPoint 2013 + Office Mix
  2. upload the new Mix to the Office Mix website, enabling offline video creation and mobile viewing
  3. downloading an .MP4 video to produce closed captions using 3rd-party services


Office Mix Closed Captions Basics

If you haven’t read up about the new Office Mix closed-captions feature, I suggest you read up about it at these two links:

Deliver Compelling Presentations Using Office Mix Slide Notes and Closed Captioning (Office Mix Team for Microsoft Office Blogs, April 14, 2015)
Office Mix – How to Add Closed Captions (Office Mix Team on Uservoice forum, continually updated tutorial)



Closed Captioning feature announcement


Using YouTube’s Subtitle Generator

To create the subtitles, I first uploaded the video version of my Office Mix to YouTube. Next, I opened the YouTube Video Manager onto the Subtitles and CC tab.

The Subtitles and CC tab of YouTube’s Video Manager


As you may know, YouTube provides automatic subtitles for videos in many languages, based on its speech recogntion technology. You can read more about this feature in YouTube Help – Automatic Captions.

The Automatic Captions feature of YouTube is the reason I first uploaded my video to YouTube. You don’t have to start from scratch, but can use the auto-generated captions provided by YouTube as your starting point.

Now, although YouTube does a fair job at speech recognition, the resulting subtitles still have to be checked and corrected manually – one by one. The YouTube caption editor is very easy to use, and probably couldn’t be made more efficient. Still, in my experience, correcting each of the captions remains a lot of work. It can help a great deal if you already have an accurate script available up front – in my case, I didn’t.

More about editing auto-captions here: YouTube Help – Edit Captions

A tiny hurdle is that YouTube doesn’t natively support the file format .TTML that is required by Office Mix, so I ended up exporting the subtitles intermediately in the .SRT format. See which subtitle formats are supported by YouTube, and why the .TTML subtitle format that is required by Office Mix isn’t one of them, in YouTube Help – Upload subtitles and closed captions


Converting subtitle file format .SRT to .TTML

The next hurdle was how to convert YouTube’s closed-captioning format .SRT to .TTML, the format required by Office Mix. I discovered that the free video captioning service Amara lets you add existing .SRT subtitle files to imported YouTube videos, and also lets you export those subtitles again in .DFXP format. The DFXP subtitle format turns out to be compatible with .TTML.

Exporting Amara subtitles into the TTML-compatible DFXP file format

Exporting Amara subtitles into the TTML-compatible DFXP file format

Two Amara help pages are relevant here:

How to add existing subtitles, captions, or transcripts to videos

How do I download subtitles and translations from a video on Amara?


Final step: adding the subtitles file to Office Mix Online

Office Mix Online requires the import file for your subtitles to have the .TTML file extension. Now that turned out easy enough: if you simply edit the file extension of the .DFXP file (downloaded from Amara) and rename it to .TTML, Office Mix Online will accept it.

Office Mix Online successfully imported the TTML file

Office Mix Online successfully imported the TTML file


Have you tried your hand at creating closed captions for Office Mix yet? How did you do it?