Soft Subtitle and Language Tracks Defined:   Subtitles may be added to .m4v video files and are most often used to provide a textual representation of spoken dialog in one language or another. Additional text to represent environmental sounds (e.g. "dog barking" or "light rock music") may also be present to assist the hearing impaired.

Subtitles may be "hard" or "soft." Hard subtitles are simply text that is permanantly "burned" onto the video during the editing process. They cannot be turned off and, so, supporting more than one language is not generally feasible. Soft subtitles, on the other hand, exist as one or more tracks that can be made visible or not visible, one at a time, by the learner. The default for soft subtitles is "None." This enables support for multiple languages as well as assistance to hearing impaired persons. Subtitles may also be used to convey textual information other than dialog and environmental sounds, things like a director's commentary or the notation of an analyst, reviewer, critic, student or teacher. Therefore, the focus here is exclusive to soft subtitles because of their greater flexibility.

Note: Closed Captions (CC), an artifact of broadcast television, are sometimes confused with soft subtitles. Although closed captions can be toggled on and off, they are confined to a single language, are difficult and expensive to make and are aesthetically lacking. Thus, closed captions will also be ignored here.

An .m4v video file may also have one or more audio tracks to accompany the video track, one for each supported language with one of those tracks being the default. These, too, can be selected by the audience one at a time. In addition to supporting more than one language, multiple audio tracks may be used to convey other audible information, such as commentary or descriptions of the video for visually impaired persons. This additional audio may be dubbed over the original dialog, musical score and environmental sounds and is especially effective where the "ducking" technique in audio applications is used. Ducking is where the onset of an announcer's voice causes other audio, such as music, to be attenuated and then recover when the announcer stops speaking.

Thus, one can develop mobile, podcastable video files with multiple soft subtitle and alternate audio tracks that audiences can mix and match to suit a variety of learning and other objectives.

Multiple Soft Subtitle & Audio Tracks in Action:   Soft subtitle and alternate audio track controls will vary by playback environment. Thus, we present the following screencasts showing how multiple soft subtitle and language tracks in .m4v files look and behave as well as how they are commonly used.

The Pedagogy of Multiple Soft Subtitle & Language Tracks:   Soft subtitles and language tracks provide those faculty, students and staff who want to publish mobile, podcastable learning materials with a number of options that can substantially enhance the value of video files in pursuing important educational objectives. The following is a partial list:

  • Accessibility (Section 508 and Section 504)
  • Language instruction
  • Film Criticism and Analysis
  • Questions to Consider at Various Points in a Video
  • Assignments In-context (along with with Chapter Tracks)
  • Annotation as a Learning Exercise
  • Learning Song Lyrics in an Unfamiliar Language
  • Additional Cues for Promoting Increased Comprehension

Major Applications of Multiple Soft Subtitle and Language Tracks:   One or more soft subtitle tracks may be added to an .m4v file for the purpose of providing alternative or additional ways to comprehend dialog and action in a movie or add information not otherwise available. Adding multiple audio tracks is often done for very similar reasons. Editing these track types is currently possible only by replacement. The methods involved will vary depending upon the video source and playback environment as well as the objectives of the project as follows:

  • Enhancing an Original Video Production with Soft Subtitles
    This is where the person adding the soft subtitle tracks is also the author of the video file content. At this time, the only Mac application with a Graphical User Interface (GUI) capable of adding both soft subtitle and extra audio tracks to .m4v files is a freeware, Mac-only tool called Subler. Subler takes as input a plain ASCII text file that carries the suffix .srt indicating that the Sub Rip Text (SRT) format has been followed in composing the file. The .srt format is quite simple and is described in this Wikipedia article and illustrated in this explainer screencast. One can create an .srt file with a text editor such as BBEdit and QuickTime Player (to identify where on the timeline a subtitle should appear) or a dedicated .srt editor such as Jubler or SubsFactory. The following screencast provides a simple example of creating an .srt file and adding it to an .m4v file as a soft subtitle track using BBEdit, QuickTime Player and Subler. The commercial application, iSubtitle, now in version 2, is quite capable and easy to use. It creates and installs soft subtitles, chapter markers and meta data. Unfortunately, it does not currently handle alternate audio tracks.
  • Enhancing an Original Video Production with Alternate Audio Tracks
    Adding alternate audio tracks is much simpler than producing them. However, developing audio tracks to support multiple languages can benefit from the earlier production of a subtitle track. Simply translate the text of the SRT file to the second language and then use that as a script for voice talent to create the second audio track and so on. Be sure to provide your voice talent with additional script notation so that they can easily differentiate their parts from others' and provide them with the opportunity to view the video as well while recording. This is the way animated movies are done and how on-location recording errors are re-recorded and corrected in the studio. The following screencast provides a simple example of creating a second language track with GarageBand and adding it to an .m4v file with Subler.
  • Repurposing an Extant Video Production with Alternate Audio Tracks
    It is common for DVDs to offer multiple audio tracks to support several languages and director commentary. The Handbrake application can now extract up to four different language tracks in addition to the DVD video and save that as an .m4v file using presets for iPhone, iPod and AppleTV among others. Handbrake will even queue multiple encodes so is an essential tool for re-purposing DVD video for educational purposes.
    The following screencast provides a typical example of the use of Handbrake to extract multiple language tracks from a DVD in addition to the video.
    While Handbrake has a subtitles feature, this is for the much less useful "hard" subtitles approach. Where the goal is to have both multiple audio tracks and multiple soft subtitle tracks, it is usually best to extract the video and audio tracks first and then extract and install the soft subtitle tracks as described next.
  • Repurposing an Extant Video Production with Soft Subtitles
    It is also common for DVDs to offer multiple subtitle tracks to support several languages that assist both the hearing impaired and those not fully conversant with the language of the selected audio track. Extracting this data into a usable format is challenging because DVD subtitle text exists as a series of bit-mapped graphic overlays. To convert these graphics into machine-readable text requires a process called Optical Character Recognition or OCR. The application D-Subtitler 1.0 does just this. It extracts the graphic overlays and timing data then uses OCR to convert that into a text file in the .srt format. Unfortunately, as with all OCR operations, the result is imperfect and usually has to be manually edited to correct errors. D-Subtitler offers some help in this area but other applications such as Jubler, BBEdit, Subs Factory and Sub Cleaner may be needed to produce an accurate and well-formed .srt file for Subler to install into the .m4v file.
    Originally, creating subtitles was the exclusive province of "fansubbers" who wanted to create subtitles in their native language for titles only available in some other language. Japanese Anime was and remains a favorite genre. Fansubbers would often add their own commentary as well. Educators owe a debt of gratitude to these early pioneers for without their enthusiasm and hard work, there would be no tools to extract extant subtitles or create new soft subtitles.
    The following screencast provides a typical example of the use of D-Subtitler to extract subtitle data from a DVD and apply OCR techniques to convert that data into machine-readable form. Also shown is the use of Jubler to review and correct the text. Subler is used to install the resulting .srt file as a subtitle track.
  • The Special Case of Soft Subtitles in Audio-only Files
    In those cses where adding soft subtitles to audio-only files is desireable, one has to first add a visual background of some sort so that the subtitle text is visible. That background can be as simple as a single monocolor graphic that displays for the duration of the audio or as complex as one or more themed photographic or other complex images appearing at specific points along the time line. The image or images chosen for this task need only be of sufficient size (400-600 pixels wide) to properly display the subtitle text for comfortable reading. Although this creates a video file, the frame rate is much lower than the typical 15-30 frames per second (fps) of a standard video file. Thus, this technique produces a much smaller file.
    The following screencast illustrates the use of QuickTime Player Pro in creating a visual backdrop for subtitles that accompany an audio track in an .m4v file. With subtitles added, this technique could be useful in providing lyrics to students learning how to sing in a language other than their primary language, point out significan events or points in music or speech, assist persons with partial hearing loss with spoken dialog and so on.
  • Lryics Metadata vs Soft Subtitles
    Of course, lyrics are also available as meta-data that are easily added to podcastable files. Any text can be inserted (lyrics, instructions, commentary, etc.). However, iTunes lyrics have two major shortcomings as compared to multiple soft subtitles. First, they are not synched to the audio as soft subtitles are. This places quite a burden on the audience where timing is important. Second, the lyrics field is confined to one version of the audio. Soft subtitles, on the other hand, can be available in multiple versions (e.g. languages, phonetic guides, etc). This is not an either/or situation. One can use the Lyrics data field to convey a substantial body of text along with the media file. Thus, the Lyrics field could be used to convey general information such as advance organizers and guides on how to approach the media while soft subtitles could provide text that is time and/or context-sensitive. The following screencast illustrates the use of the Lyrics field in the iTunes.app for other kinds of data besides traditional song lyrics.


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