ffmpegX is a command line tool that allows to embed subtitles or open captions in your media files. This tutorial shows how to use this tool via Mac GUI (there are GUI versions for both Windows and Mac OS X).
ffmpegX is an encoder and it will take several different types of video formats as source input and will transcode the video to a different target format as needed, using "filters" to transform the video. However, be aware that not all of the target formats included with ffmpegX allow burning in open captions. AVI DivX, which is the default target format for ffmpegX, is one that does allow burn-in, but for this article we will show the process using "h.264 mencoder." This selection allows you to create an MP4 video with open captions or burned-in subtitles that is compatible with players on both Windows and Mac OS X.
After you've made your captioning request, download the SRT format from your CaptionSync account. Start ffmpegX, click Open and select your source video. Next, under the Target format pane, select h.264 mencoder from the pull-down list next to To. The result should look like the screenshot below.
Next, click on the Filters tab and then Load subs. Select the SRT file that contains the captions or subtitles that you want to burn in to the video. Leave the option Burn selected at the top of the Subtitles pane. Note that you can adjust the fonts and font sizes, to some extent. You can also adjust the vertical position (Pos). The default value of 80 positions the captions 80 percent down the screen. If you want them lower, you can try a larger value such as 90 (the attached sample video used a value of 90). You can preview the positioning and fonts using the Play button on the upper right.
When you are satisfied with your settings, click Encode. The resulting video will have burned-in captions or subtitles. You can download the attached sample video for an example with open captions in English encoded using ffmpegX.