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ISO/IEC 13818-1:2015/Amd 6:2018 – Carriage of High Dynamic Range and Wide Color Gamut Content in MPEG-2 Transport Streams
Technical overview of the amendments introduced by IEC 13818-1-16 (Amd 6:2018) for HDR/WCG signaling in digital television infrastructures
Scope
ISO/IEC 13818-1:2015/Amd 6:2018 — the sixth amendment to the systems part of the MPEG-2 standard, often informally referred to as IEC 13818‑1‑16:2018 — specifies syntax and semantics extensions to the MPEG-2 Transport Stream (TS) for the reliable carriage of high dynamic range (HDR) and wide color gamut (WCG) video content. The amendment is primarily intended for broadcast and packaged media applications that need to convey HDR/WCG metadata together with compressed video streams based on advanced codecs such as HEVC (H.265) and AVC (H.264).
Key additions include new descriptors, extended value ranges for existing colour‑related fields, and backward‑compatible signaling mechanisms that allow legacy decoders to safely ignore HDR/WCG metadata while enabling HDR‑capable receivers to reconstruct the full dynamic range and color volume of the original production content.
Technical Requirements
The amendment introduces several normative changes to the MPEG‑2 Systems specification (ISO/IEC 13818‑1), focusing on descriptors and program‑specific information (PSI) tables. The core requirements are organized into three categories.
High Dynamic Range and Wide Color Gamut Signaling
To signal the presence and characteristics of HDR/WCG video, the amendment extends the existing Video Stream Descriptor by adding four new entries in the colour_primaries field (e.g., BT.2020, DCI‑P3), five new values in transfer_characteristics (including Hybrid Log‑Gamma and Perceptual Quantization), and two new matrix_coefficients. These allow the encoder to precisely specify the colorimetry of the HDR content.
In addition, two entirely new descriptors are defined:
- Mastering Display Colour Volume Descriptor – carries the color primaries, white point, and luminance range (max/min) of the monitor used during mastering.
- Content Light Level Information Descriptor – provides the maximum frame‑averaged light level (MaxFALL) and the maximum content light level (MaxCLL) of the sequence.
New Descriptors and Syntax
The following table summarizes the main fields added or modified by ISO/IEC 13818‑1:2015/Amd 6:2018:
| Descriptor / Field | Tag | Purpose | Payload (bytes) |
|---|---|---|---|
| Mastering Display Colour Volume | 0x36 | Communicates mastering display color primaries and luminance range | 24 |
| Content Light Level Information | 0x37 | Provides MaxCLL and MaxFALL values of the content | 4 |
colour_primaries (Video descriptor) | — | Extended to include BT.2020, DCI‑P3, ACES, etc. | 1 byte (new values) |
transfer_characteristics (Video descriptor) | — | Extended to support HLG, PQ, and other HDR EOTFs | 1 byte (new values) |
Tip: When implementing these descriptors, ensure that the carriage of metadata does not exceed the maximum descriptor length (255 bytes) and that decoding devices verify the presence of both Mastering Display Colour Volume and Content Light Level Information for complete HDR subtitle and graphics mixing workflows.
Backward Compatibility
All new descriptors are registered in the Program Map Table (PMT) and may be ignored by receivers that do not support HDR. The amendment explicitly prescribes that the presence of HDR descriptors must not alter the fundamental demultiplexing of the Transport Stream. Legacy decoders will drop the unrecognised descriptor tags without affecting audio, video, or other elementary streams.
Implementation Highlights
Adoption of this amendment in broadcast infrastructure and consumer devices involves updates throughout the delivery chain.
- Multiplexer / Encoder: The TS multiplexer must be configured to insert the new descriptors in the PMT for each video stream carrying HDR content. The mastering display metadata and content light levels should be extracted from upstream processing or manually specified during encoding.
- Transmitter / Headend: No change required in the physical layer. The descriptors are part of layer‑3 (system) metadata and pass transparently through remultiplexers, as long as the descriptor tags are not filtered out.
- Receiver / Decoder: HDR‑capable chipsets must parse the new descriptor tags and use the contained values to set display parameters. For HEVC streams, the amendment aligns with the HDR metadata already standardised in ISO/IEC 23008‑2 (HEVC), but carries it inside TS‑specific descriptors for backward compatibility.
Important: When remultiplexing TS streams from different sources, ensure that the
Mastering Display Colour Volume descriptor is not duplicated or stripped. Mismatched metadata can lead to incorrect color volume mapping on the receiver side. Bandwidth and Performance Considerations
The combined overhead of the two new descriptors is approximately 28 bytes per video elementary stream in the PMT. Since PMT tables are sent periodically (typically every 100 ms), the additional bandwidth is negligible – about 2.2 kbps per stream. For live production, encoders should recompute the MaxCLL and MaxFALL values from the incoming HDR signal on a scene‑by‑scene basis to avoid static metadata.
Compliance Notes
Testing compliance with ISO/IEC 13818‑1:2015/Amd 6:2018 involves verifying both the syntax and semantic correctness of the new descriptors as well as their interaction with the existing Transport Stream structure.
Conformance Testing
Three levels of conformance are typically considered:
- Syntax conformance: The descriptor tags (0x36, 0x37) are correctly placed inside the PMT, and each field adheres to the specified lengths and ranges.
- Semantic conformance: The numerical values for colour primaries, transfer characteristics, and mastering display parameters fall within valid ranges as defined in the amendment. For example, the encoded chromaticity coordinates must represent actual CIE 1931 xy values.
- System conformance: The Transport Stream with HDR descriptors can be demultiplexed and decoded without errors by a reference implementation, and the HDR metadata is correctly passed to the video decoder.
Good practice: Manufacturers are encouraged to participate in industry plug‑fests (e.g., DVB, CableLabs) that validate HDR signaling interoperability across different multiplexers and receivers.
Versioning and Maintenance
The amendment is fully upward compatible. Implementations that claim conformance to ISO/IEC 13818‑1:2015 do not need to alter their core demultiplexing logic. However, to claim support for HDR/WCG under this amendment, a decoder must:
- Recognise and parse descriptor tags 0x36 and 0x37;
- Interpret the extended EOTF and colour space values; and
- Apply the metadata to colour conversion and display rendering only when the video codec also conveys HDR capability.
Caution: While the amendment is backward compatible, mixing HDR descriptors from different editions (e.g., pre‑2018 proprietary extensions) can cause conflicts. Always rely on the normative descriptor tags defined in the final published amendment.
Frequently Asked Questions
Q: What is the exact change introduced by ISO/IEC 13818‑1:2015/Amd 6:2018?
A: The amendment adds two new descriptors (Mastering Display Colour Volume and Content Light Level Information) and expands several colour‑related fields in the Video Stream Descriptor. These additions allow MPEG‑2 Transport Streams to carry the metadata needed for high dynamic range and wide colour gamut content, primarily targeted at UHD‑TV broadcast services.
A: The amendment adds two new descriptors (Mastering Display Colour Volume and Content Light Level Information) and expands several colour‑related fields in the Video Stream Descriptor. These additions allow MPEG‑2 Transport Streams to carry the metadata needed for high dynamic range and wide colour gamut content, primarily targeted at UHD‑TV broadcast services.
Q: Does this amendment apply only to HEVC streams?
A: No. The descriptors can be used with any video codec carried over Transport Streams. However, they are most often paired with HEVC because that codec already supports similar HDR metadata in its Video Usability Information (VUI). The amendment aligns TS signaling with the HDR metadata defined in HEVC to avoid duplication.
A: No. The descriptors can be used with any video codec carried over Transport Streams. However, they are most often paired with HEVC because that codec already supports similar HDR metadata in its Video Usability Information (VUI). The amendment aligns TS signaling with the HDR metadata defined in HEVC to avoid duplication.
Q: How does this amendment relate to other HDR standards, such as ITU‑R BT.2100 or SMPTE ST 2084?
A: The amendment references the same colour spaces and electro‑optical transfer functions defined in these international standards. In particular, the
A: The amendment references the same colour spaces and electro‑optical transfer functions defined in these international standards. In particular, the
transfer_characteristics values for Hybrid Log‑Gamma (HLG) and Perceptual Quantization (PQ) are taken directly from ITU‑R BT.2100‑1, while mastering display data follows SMPTE ST 2086 conventions. Q: I am developing a TS analyser. What is the simplest way to test if a stream conforms to this amendment?
A: Look for descriptor tags 0x36 and 0x37 in the PMT of a video elementary stream that also reports an HEVC or AVC coding type. Validate the payload lengths (24 and 4 bytes, respectively) and verify that the
A: Look for descriptor tags 0x36 and 0x37 in the PMT of a video elementary stream that also reports an HEVC or AVC coding type. Validate the payload lengths (24 and 4 bytes, respectively) and verify that the
colour_primaries and transfer_characteristics in the Video Stream Descriptor correspond to HDR values (e.g., >9 for colour primaries and >16 for transfer characteristics). — Produced from the normative text of ISO/IEC 13818‑1:2015/Amd 6:2018 and industry best practices. Revision date: 2026.