MPEG-4 Part 17
Encyclopedia
MPEG-4 Part 17, or MPEG-4 Timed Text, or MPEG-4 Streaming text format is the text based subtitle
Subtitle (captioning)
Subtitles are textual versions of the dialog in films and television programs, usually displayed at the bottom of the screen. They can either be a form of written translation of a dialog in a foreign language, or a written rendering of the dialog in the same language, with or without added...

 format for MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...

, published as ISO/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...

 14496-17 in 2006. It was developed in response to the need for a generic method for coding of text as one of the multimedia components within audiovisual presentations.

It is also streamable, which was one of the main aspects when creating the format. It is mainly aimed for use in the .mp4
MPEG-4 Part 14
MPEG-4 Part 14 or MP4 is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital video and digital audio streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images...

 container, but can also be used in the .3gp
3GP
3GP is a multimedia container format defined by the Third Generation Partnership Project for 3G UMTS multimedia services. It is used on 3G mobile phones but can also be played on some 2G and 4G phones....

 container (as 3GPP Timed Text), which is technically almost identical with .mp4 but more used in cell phones. 3GPP Timed Text is exactly the same as MPEG-4 Timed Text when used in the .mp4 container. It can be also used in other file formats based on the ISO base media file format
ISO base media file format
ISO base media file format defines a general structure for time-based multimedia files such as video and audio. It is used as the basis for other media file formats...

.

3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...

 approved the Timed text format for 3G
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...

 multimedia services in 3GPP TS 26.245 in 2004. MPEG-4 Part 17 (ISO/IEC 14496-17:2006) defined Text Streams that are capable of carrying 3GPP Timed Text. For 3GPP text streams, ISO/IEC 14496-17:2006 defined a generic framing structure suitable for transport of 3GPP text streams across a variety of networks (RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...

 and MPEG transport stream and MPEG program stream). The framing structure for text streams consists of so-called Timed Text Units (TTU).

Supporting implementations

QuickTime Pro
QuickTime
QuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...

 and MP4Box can create or produce these kind of subtitle streams out of various subtitle input formats. MP4Box uses the fourcc
FourCC
A FourCC is a sequence of four bytes used to uniquely identify data formats.The concept originated in the OSType scheme used in the Macintosh system software and was adopted for the Amiga/Electronic Arts Interchange File Format and derivatives...

 tx3g for MPEG-4 Timed Text because of its inherently higher compatibility. MPEG-4 Timed Text is heavily based on XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

 semantics.

On October 7, 2005, VideoLAN
VideoLAN
VideoLAN is a project that develops software for playing video and other media formats across a local area network . It originally developed two programs for media streaming, VideoLAN Client and VideoLAN Server , but most of the features of VLS have been incorporated into VLC, with the result...

 added decoding support for MPEG-4 Timed Text subtitles in VLC
VLC media player
VLC media player is a free and open source media player and multimedia framework written by the VideoLAN project.VLC is a portable multimedia player, encoder, and streamer supporting many audio and video codecs and file formats as well as DVDs, VCDs, and various streaming protocols. It is able to...

.

On October 30, 2005, Gabest added decoding support for MPEG-4 Timed Text subtitles in MPC
Media Player Classic
Media Player Classic is a compact media player for 32-bit and 64-bit Microsoft Windows. The application mimics the look and feel of the old, lightweight Windows Media Player 6.4 but integrates most options and features found in modern media players...

.

External links

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