SIST ETS 300 472 E1:2005

SIST ETS 300 472 E1:2005 is a Slovenian adoption of an ETSI/EBU standard for carrying ITU-R System B Teletext, also known as EBU Teletext and World System Teletext (WST), in DVB bitstreams. It specifies the packet syntax and timing needed to move teletext and teletext subtitles through MPEG-2 transport streams for broadcasters, multiplex operators, and receiver or decoder manufacturers.

What does SIST ETS 300 472 E1:2005 specify?

SIST ETS 300 472 E1:2005 specifies how ITU-R System B Teletext can be transported in DVB bitstreams. Its scope is limited to teletext carriage that can be transcoded back into the Vertical Blanking Interval (VBI) of analogue video, with a per-service data rate equivalent to 16 lines per field and timing accurate enough for subtitles near frame accuracy.

The standard also says that the transport syntax can be adapted for other data, but it is not a general-purpose data transport specification.

The document is organized into scope, normative references, definitions and abbreviations, insertion of teletext into the MPEG-2 transport multiplex, and a teletext decoder model.

What are the key requirements of SIST ETS 300 472 E1:2005?

SIST ETS 300 472 E1:2005 uses a defined MPEG-2 carriage structure and tight packet rules so teletext can be identified, timed, and, if needed, transcoded back to analogue VBI. Clause 4 sets the packet syntax, and Clause 5 sets the decoder timing model.

Carriage and signalling

• Teletext data are carried in Packetized Elementary Stream (PES) packets inside Transport Stream packets, and the Program Map Table (PMT) identifies the Packet Identifier (PID) for each teletext stream. In practice, this is how a receiver finds the teletext service inside a DVB multiplex.
• The teletext stream_type is 0x06, meaning private data, and the teletext descriptor from ETS 300 468 appears in the Program Specific Information (PSI) for that service. In practice, this tells the receiver that the private data is teletext, not another proprietary stream.
• A service may carry more than one teletext data stream if each stream uses a different data_identifier and the streams can be distinguished by their teletext descriptors. That matters when a service separates subtitle and non-subtitle teletext.

Packet syntax constraints

• In Clause 4.1, only Transport Stream adaptation_field_control values 01 and 10 are permitted. That keeps the teletext carriage within the expected MPEG-2 transport structure.
• In Clause 4.2, PES packets use stream_id private_stream_1, a fixed PES_header_data_length of 0x24, and a PES_packet_length chosen so the packet ends at the end of a Transport packet. The data_alignment_indicator is set to 1, which keeps access units aligned for decoding.
• In Clause 4.3 and 4.4, the PES data field uses a fixed data_identifier for a stream, and only data_unit_id values 0x02, 0x03, and 0xFF are allowed for streams identified by the DVB teletext descriptor. This separates ordinary teletext, teletext subtitles, and stuffing.
• For EBU Teletext data units, data_unit_length is fixed at 0x2C, and line_offset is restricted to values that correspond to usable VBI line positions. That is what makes the stream suitable for transcoding back into analogue teletext insertion lines.
• The framing_code, magazine_and_packet_address, and data_block fields carry the 43 bytes that follow the clock-run-in sequence in the original teletext packet, and packets are inserted in presentation order. This preserves the teletext packet sequence expected by the decoder.

Timing and decoder model

• Clause 5 treats a teletext access unit as a teletext data packet, and the Presentation Time Stamp (PTS) applies to the first access unit after the PTS field. In practice, this is what keeps teletext subtitles aligned with the video.
• The target decoder model uses buffers TBttx = 480 bytes and Bttx = 1 504 bytes, a transfer rate of 6.75 Mbit/s, and a maximum residence time of 40 milliseconds in Bttx. Encoders and multiplexers therefore need to keep teletext moving through the system on that timing budget.
• For transcoding, an access unit is released when the matching video line and field parity are available and the system clock has reached the relevant PTS. For direct decoding, release happens when a complete access unit is available and the PTS condition is met.

What terms does SIST ETS 300 472 E1:2005 define?

• MPEG-2 - The standard ISO/IEC 13818, used here for systems coding, video coding, and audio coding.
• Section - A syntax structure used to map service information into ISO/IEC 13818 Transport Stream packets.
• Service - A sequence of programmes under broadcaster control that can be scheduled and broadcast together.
• Teletext descriptor - A descriptor in the PMT that identifies streams carrying EBU data.
• Packetized Elementary Stream (PES) - The packet layer used here to carry teletext data before it is placed into Transport Stream packets.
• Presentation Time Stamp (PTS) - The timestamp that controls when decoded text is presented or transcoded into the VBI.
• Vertical Blanking Interval (VBI) - The part of analogue video used for teletext transcoding and compatibility with legacy receivers.

Who uses SIST ETS 300 472 E1:2005?

SIST ETS 300 472 E1:2005 is used by broadcasters, multiplex operators, transmission engineers, and receiver or decoder manufacturers. They use it when signalling teletext in DVB, packetizing the data, checking subtitle timing, and making sure teletext can still be transcoded into analogue VBI for existing TV receivers.

It is also relevant to teams that test interoperability, because the standard defines both the carriage syntax and the decoder timing model that implementations are expected to satisfy.

What changed in SIST ETS 300 472 E1:2005 from the previous edition?

SIST ETS 300 472 E1:2005 corresponds to ETS 300 472 Edition 1. The document history identifies it as the first edition.

Which standards are used with SIST ETS 300 472 E1:2005?

• ISO/IEC 13818-1 (1994) - Provides the MPEG-2 systems model and Transport Stream/PES framework used for carriage.
• ETS 300 468 - Provides Service Information (SI), including the Program Map Table and the teletext descriptor used to signal teletext streams.
• ITU-R Recommendation 653 - Defines System B, 625/50 teletext packet structure referenced for the teletext payload.
• EBU SPB 492 (1992) - Provides the 625-line teletext specification used together with ITU-R Recommendation 653.

What does the SIST ETS 300 472 E1:2005 document contain?

SIST ETS 300 472 E1:2005 contains packet-format rules for Transport Stream and PES carriage, plus syntax tables for the teletext payload. It also includes tables that define the allowed values of fields such as data_identifier, data_unit_id, and line_offset.

The document gives the structure of the EBU Teletext data field and explains how its bytes map to the original teletext packet fields. It uses those structures to support both decoding on a receiver and transcoding back to the VBI.

Clause 5 adds a conceptual decoder model with buffer sizes, transfer rate, and timing rules. That part is used to judge whether an implementation can present teletext and subtitles at the right time.