The MPEG-4 Standard:   The MPEG-4 Standard is the latest work of the Moving Picture Experts Group and represents the current state-of-the-art in video compression, display and interactivity. Its development and deployment is still unfolding. MPEG-4 is of particular interest here because it is a key technology in Mobile Learning (mLearning) via the free, cross-platform iTunes application, the "classic" iPods and, now, for devices such as the iPhone and iPod touch as well as the AppleTV set top box. MPEG-4 files normally have a file name suffix of .mp4 but those with special attributes may instead have an .m4a, .m4v, .m4b or .m4p file name suffix which helps assure proper handling and presentation of those special attributes.

QuickTime and MPEG-4:   MPEG-4 is based upon the QuickTime track-based file system and the MPEG-4 road map calls for it to eventually do all that QuickTime does now and then some. For the present, however, we are in a transitional period where both architectures are necessary to being competitive and productive in the mLearning space. For example, mobile devices such as the iPhone and iPod touch use firmware that understands only certain aspects of MPEG-4 and very little of QuickTime. Transparent interoperability via on-the-fly translations minimize these differences from the audience's perspective but educational content and application developers need to be aware of them in order to make the best use of these technologies and provide superior learning experiences.

Thus, the differences between QuickTime and MPEG-4 containers need to be carefully considered where educational programs make use of podcasting, mLearning and other environments. At present, the QuickTime .mov container provides far more interactivity, better immersive experience and a wider range of CODEC and format support, including the most recent MPEG-4 video and audio CODECs: H.264 and AAC. On the other hand, many of these advanced QuickTime features such as QuickTime Virtual Reality (QTVR or VR) cannot be played by the Videos.app on video iPods, the iPhone, iPod touch nor on the AppleTV because the MPEG-4 firmware CODECs in these devices cannot yet understand virtual reality and several other important advanced techniques.

Adding to the potential confusion is the fact that the iTunes application, which is based largely on QuickTime and is the gateway to the iPod, iPhone, iPod touch and AppleTV, will play some media that these devices cannot play. So the iTunes app will play media that it will subsequently refuse to synchronize to an iPod, iPhone, iPod touch or AppleTV. What's more, the iTunes application will not properly play all QuickTime media as the QuickTime Player and other QuickTime-based applications will.

It gets even more interesting and confusing when you consider the fact that there are like-named functions in both QuickTime .mov containers and in MPEG-4 files, especially the .m4v file type used for video in the iPod, iPhone, iPod touch and AppleTV. These functions include Chapter Markers, Alternate Audio (Language) Tracks, Soft Subtitle Tracks and Poster Frames (treated here). Closed Captioning, a vestige of broadcast television, is not treated here because it is redundant of and inferior to soft subtitle tracks. The methods one would use to create Chapter Markers, Alternate Audio Tracks, Soft Subtitle Tracks and Movie Poster Frames in a QuickTime .mov container are completely different from the methods one needs to employ in order to create similar effects in an .m4v container. Yet, they will look and behave almost identically to your audiences.

What throws many content developers is the similarity in appearance of these features in .mov and .m4v files when viewed in the QuickTime Player. Take Chapter Markers, for example. One can easily come to the erroneous conclusion that they are interchangable. In the QuickTime Player, they look and behave exactly the same regardless of whether it is a .mov or .m4v file. However, if you create a chapter track containing chapter markers in a QuickTime .mov file and then Export to iPod format using QuickTime Player Pro, the chapter track is lost. Ditto for soft subtitle tracks, alternate audio tracks and movie poster frames. Conversely, .m4v files loose their chapter markers, soft subtitle tracks, alternate audio tracks and album art when being saved as a .mov file. It gets worse. Make even minor changes in a .m4v file (e.g. edit a movie annotation) and you will be forced to save it as a .mov file which will then strip out Chapter Tracks, etc. It cannot be saved in place. I believe that this last item is a bug (MPEG-4 Exporter handles only one audio and one video track) and I have entered an Apple bugreport on it (6693000).

Current Solutions:   Documentation and applications for creating Chapter Tracks, Subtitle Tracks, Alternate Audio Tracks and Movie Poster Frames in .mov containers are plentiful. Here is a brief sample listing:

Creating equivalent structures in .m4v files for podcasting and mLearning is much less well known and, thus, deserving of extensive further explanation and illustration. Consequently, you will find four separate sections that are accessible from the links that appear in the menu in the upper right-hand column of this page:
  • Chapter Marker Tracks (plus HREF Tracks)
  • Soft Subtitle Tracks (plus Alternate Audio Tracks)
  • Cover Flow "Art"
  • Metadata

QuickTime 1.0 debuted in December, 1991 and is now in version seven (7.6 as of this writing). It has a long history and backward compatibility has been more or less maintained throughout this period. However, backward compatibility eventually becomes untenable. That point appears to have been reached with the advent of QuickTime X (MacOS X 10.6 only as of this writing).

QuickTime X is not backward compatible in many areas such as QTVR and "wired" QuickTime. Although QuickTime Player 7.6 is also available in MacOS X 10.6 (Snow Leopard) to support "legacy" media and continues to be available for earlier versions of MacOS X and Windows XP or newer, it is clear that the future of QuickTime will be based upon QuickTime X. The road map for that future, if one exists, is known only to a few key people at Apple, Inc. However, it is already quite clear from looking at the current iteration of QuickTime X that MPEG-4 technologies such as the H.264 and AAC CODECs are central to that future and that there will be a fairly substantial transition period before QuickTime X is fully in place.

Thus, content and application developers will need to keep a foot in both camps but use QuickTime X and MPEG-4 technologies wherever they can so as to assure the greatest longevity of their work and leverage the advanced capabilities of MPEG-4.