ISO/IEC 14496-17:2006 PDF
Information technology — Coding of audio-visual objects — Part 17: Streaming text format
Information technology — Coding of audio-visual objects — Part 17: Streaming text format
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 21
- Дата публикации:
- 23 марта 2006 г.
- Издание:
- ISO/IEC IS 14496 edition 1 version 1
- ICS:
- 35.040
ISO/IEC 14496-17:2006 was developed in response to the need for a generic method for coding of text at very low bitrate as one of the multimedia components within an audiovisual presentation. ISO/IEC 14496-17:2006 allows for example subtitles and Karaoke song texts to be coded and transported as separate text streams at bitrates that are sufficently low for use in mobile services over IP. Target applications are in particular found in areas with severe transmission bandwidth constraints, such as mobile services over IP. However, services over broadband IP, over broadcast channels and over optical media may also benefit from the low bandwidth of ISO/IEC 14496-17:2006 text streams. ISO/IEC 14496-17:2006 specifies a text stream as a concatenation of text access units. A text access unit contains text information of a specific format. For each text stream, the format of the text information within the text access units is signalled. Each text access unit within a text stream is intended to be displayed at a specific instance in time. Note that ISO/IEC 14496-17:2006 signals the format of the text contained in text access units, but that it does not contain any text format specification. Within ISO/IEC 14496-17:2006, a particular instance of text streams are 3GPP text streams. Each text access unit contained in a 3GPP text stream carries 3GPP Timed Text data, as specified in 3GPP TS 26.245. For 3GPP text streams, ISO/IEC 14496-17:2006 defines a generic framing structure suitable for transport of 3GPP text streams across a variety of networks, such as RTP for transport over IP, and MPEG-2 Systems for use in media such as broadcast and optical discs. The flexible framing structure for text streams, consisting of so-called TTUs (Timed Text Units), allows for easy and convenient adaptation to the various transport layers. By using TTUs, multiple small text access units can be aggregated into one transport packet, but TTUs can also be used to fragment large text access units across multiple transport packets, while providing a reasonable level of error resilience in case of packet loss or non-recoverable packet errors. For each transport layer, the most suitable TTU structure can be chosen. If so desired, the text access units can be re-partitioned into TTUs for most effective adaptation to other transport systems.
Abstract
Overview - ISO/IEC 14496-17:2006 (Streaming text format)
ISO/IEC 14496-17:2006 defines a transport-agnostic streaming text format for timed presentation of textual data in audiovisual services. It provides a low-bitrate, byte-stream representation for subtitles, karaoke lyrics and other timed text components that can be carried as separate streams alongside audio/video. The standard specifies the concept of text streams, text access units, and a decoder configuration (TextConfig) that signals the text data format (for example, 3GPP Timed Text). It focuses on efficient carriage, timing, random access and reasonable error robustness for bandwidth-constrained networks such as mobile IP.
Key topics and technical requirements
- Text stream and access unit model: A text stream is a byte stream carrying sequential text access units; each access unit has a single timestamp that specifies when it must be presented.
- TextConfig: A configuration box that signals the textFormat (e.g., 0x01 = 3GPP Timed Text) and format-specific parameters required by the decoder.
- 3GPP text support: The standard defines how 3GPP Timed Text (per 3GPP TS 26.245) is carried - including text samples, text strings (UTF-8/UTF-16) and text modifiers, plus sample descriptions (fonts, positioning).
- Framing for transport (TTU): Introduces Timed Text Units (TTUs) - a flexible framing structure to aggregate small text access units into larger transport packets or to fragment large units across packets, improving adaptation to different transports and error resilience.
- Transport-agnostic signaling: Specifies usage within MPEG-4 (streamType 0x0D, objectTypeIndication 0x08) while allowing transport over RTP, MPEG-2 Systems, optical media or other IP/broadcast systems.
- Interleaving and in-band sample descriptions: Allows sample descriptions to be carried in-band or out-of-band; each text sample refers to one sample description index.
Applications and who uses it
- Mobile service providers and streaming platform engineers needing low-bitrate subtitles and timed text for bandwidth-limited networks.
- Broadcasters and OTT providers implementing subtitle/closed-caption carriage over RTP, MPEG-2 Systems or MP4-based workflows.
- Device manufacturers and media player developers building timed-text decoders compatible with MPEG-4 systems and 3GPP timed text.
- Content creators for Karaoke, accessibility (hard-of-hearing captions), multi-language subtitle distribution, and lightweight standalone text streaming services.
Related standards
- ISO/IEC 14496 (MPEG-4) family - particularly Part 12 (ISO base media file format) and Part 14 (MP4 file format) for storage/packaging.
- ISO/IEC 14496-18:2004 (Font compression and streaming)
- 3GPP TS 26.245 (Timed Text format) - defines the timed text sample and modifier formats referenced by this part.
- Transport systems referenced: RTP, MPEG-2 Systems (for broadcast/optical media transport)
Keywords: ISO/IEC 14496-17, streaming text format, timed text, TTU, 3GPP Timed Text, subtitles, low bitrate, TextConfig, text access unit, MPEG-4.
Технические детали
- Технический комитет
- ISO/IEC JTC 1/SC 29 - Coding of audio, picture, multimedia and hypermedia information
- SKU
- ISO/IEC 14496-17:2006
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