MP4/M4V Playback Issues

How do I turn on Subtitles on my Player?

Not all players display subtitles with a MP4 video. This is the case for Windows Media Player, for instance. However, display of encoded subtitles is supported by many mp4 players, including the iOS devices, AppleTV, iTunes, QuickTime, JW Player, Flow Player, VLC, RealPlayer, and many others. Learn more about how to turn on subtitles on some of the most common players.

Why doesn't my player display subtitles when the extension is MP4?

Some players, like iTunes and QuickTime on Windows, need the file to have the .m4v extension to display the subtitles. So, after you download the encoded output, ensure you change the extension to .m4v.

Why am I seeing frame skipping when watching my video?

Playing back an MP4 video is a very CPU intensive task. Presenting subtitles to the display just adds extra work to do. As a result, you may experience some frame skipping (the video decoder is trying to keep up) which was not evident before turning subtitles on. Even if there was frame skipping before subtitles, the same solutions below apply. QuickTime playback on Windows (including iTunes) and first generation iPads seem more susceptible to this.

There are three broad solutions:

• Use decoding software that employs the computing resources more efficiently. E.g. VLC Player for Windows seems to do a better job than QuickTime on Windows.
• Make the video encoding less challenging for the existing computing resources. E.g. Encode at 720 instead of 1024 HD.
• Get more computing resources. E.g. Use an iPad2 instead of iPad, use a computer with an i7 CPU instead one with a Core Duo CPU.