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Embedding Captions in MP4 Video

By: Brent Robertson
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At long last MPEG4 H.264 video has emerged as the pervasive standard for web video. For example, Flash players like JW Player and Flowplayer use .F4V files, iPads, iPods, and iPhones use .M4V files, and desktop players such as QuickTime, Windows Media Player, VLC Player, and RealPlayer can play .MP4 files. Though it took a while (and there are a variety of filename extensions) there’s never been this degree of convergence around a web video standard as this before!

Subtitling or SDH (Subtitling for the Deaf and Hard-of-hearing) is also becoming similarly standardized in H.264 video. All of the aforementioned players (except unfortunately Windows Media Player) also support the display of subtitle tracks embedded directly in the H.264 video. Multiple tracks can be added too, so you can have translated versions such as Spanish to expand your audience reach. [See more about captioning other languages and details about our coming translation service in this week’s newsletter.]

Embedding the subtitles into H.264 video also makes your life a lot easier. Embedding eliminates extra caption files that need to be moved around, could get lost, or could get corrupted in email. There is however a bit of work involved in doing the embedding yourself. The easy part is getting caption files in the correct format — but you already know to go to AST for that.

So with all this convergence around a standard (which is pretty rare in the web world), wouldn’t it be great if there was a easy way to get the subtitles and have them embedded into H.264 video for you?

AST’s Video Encoding service fills that gap. Before you upload a M4V, MP4, F4V, or MOV you can add Video Encoding via the Advanced Settings button on the submission page.

There are two options with Video Encoding: Subtitle Tracks or Open Captions. Subtitle Tracks are very flexible, and users can select them to appear or disappear at will via their player. With Open Captions part of the video information is overwritten by captions, but this leaves you with a video that is guaranteed to display captions even when using “unhelpful” players. Open Captions are also helpful for applications where you need to ensure the captions are always being displayed.

Once selected, your Video Encoding choice will show on the yellow Summary Sticky before you submit.

The resulting M4V file is typically too large to email, so you will receive an email when it is ready to download (unless you’ve disabled receiving these emails on the Contact Settings page).

Pricing for Post-Production Captioning can be found on your supplemental services price sheet on the help page. Please feel free to comment here on the blog and let us know how we can make it even more useful for you!