IEC TS 63499:2024
Encoding guidelines for interoperable master format - Application #6
- Standard No.
- IEC TS 63499:2024
- Release Date
- 2024
- Published By
- International Electrotechnical Commission (IEC) IX / IEC
- Latest
- IEC TS 63499:2024
- Introduction
Standard Overview and Technical Background
IEC TS 63499:2024 is a technical specification developed by the International Electrotechnical Commission (IEC) that provides video coding guidelines for Interoperable Master Format (IMF) Application 6. Published in February 2024, this standard is the product of TA 6, a subcommittee within IEC Technical Committee TC 100, focusing on storage media, data structures, and system equipment.
With the rapid growth of ultra-high-definition television (UHDTV) content, broadcasters face the dual challenges of processing time and storage capacity. IMF Application 6 (SMPTE ST 2067-60) is designed to address these challenges, optimizing the workflow of master program files through file-based operations. For example, when editing and revisions are required in the later stages of production, rendering and quality control can be performed on only the modified frames, avoiding reprocessing the entire film and significantly improving efficiency.
IMF framework structure and technical advantages
The Interoperable Master Format is a file-based workflow component framework used to provide interchangeable final master files. The core components of IMF include:
Component Name Function Description Technical Specifications Image Track File Stores video encoding data in frame packaging MXF OP1a format Composition Playlist (CPL) Points to each element file and contains timeline-related metadata SMPTE ST 2067-2 Asset Map Provides location information of all necessary files SMPTE ST 2067-3 Packaging List (PKL) Contains a list of all files in the IMP SMPTE ST 2067-4 IMF's primary advantages lie in file management and storage capacity. As shown in Figure 3, when a program has multiple versions (e.g., different language audio tracks) but the same video content, traditional methods require generating complete files separately. However, the IMF approach can significantly save storage space by including common elements in a single package.
AVC/H.264 Coding Constraints
Chapter 5 of the standard details the AVC/H.264 encoding constraints within IMF applications6. These constraints are designed to provide fast access to target pictures and reduce decoder complexity.
GOP structure constraints
According to the recommendations of SMPTE ST 381-3 Annex C, Long GOP streams should meet the following constraints:
- All P frames should contain only P slices, and all B frames or Br frames should contain only B slices
- The first access unit in coding order should be an IDR or non-IDR I frame in the GOP
- The key frame corresponding to each picture in the GOP should exist in the same GOP or the previous GOP
- P frames should not reference B frames
- The coding order of all I frames and/or P frames should be the same as the display order
These constraints make the GOP structure equivalent to MPEG-2 (except Br frames), so that variable rate decoding and editing techniques developed for MPEG-2 can be applied to AVC/H.264 video streams.
Parameter Set (SPS/PPS) Configuration Guide
Sequence Parameter Set (SPS) and Picture Parameter Set (PPS) contain key information required to decode AVC/H.264 compressed streams. The standard provides three implementation schemes:
Configuration scheme Technical features Applicable scenarios Advantages and disadvantages analysis Starting position of each frame SPS/PPS is placed at the beginning of the access unit of each picture Scenarios with frequent video editing Easy editing but parameter redundancy Starting position of each GOP SPS/PPS is placed in the access unit of the starting I frame of each GOP Long GOP stream decoding High decoding efficiency, support for GOP-level editing Stream starting position SPS/PPS are placed only in the access unit at the beginning of the stream Parameter sequences are constant Easy to encode, but requires additional processing during editing SMPTE ST 381-3 defines metadata elements in the AVC subdescriptor within the MXF header metadata to identify the implementation of SPS and PPS in AVC/H.264 streams. Decoders can identify the parameter set configuration by referencing these metadata elements.
Technical Analysis of Multi-Slice Coding
Multi-slice coding divides a picture into multiple slices for encoding, which is important for achieving high-speed video decoding on multi-core processors. The standard recommends using 4 to 16 slices for UHDTV pictures.
Advantages of Parallel Processing
Since the decoding process for each slice is essentially independent (except for deblocking filtering), it can be performed in parallel. The prevalence of multi-core processors in modern computers enables high performance in both hardware and software through parallel processing.
Encoding Challenges and Quality Control
Multi-slice encoding also presents challenges: it is necessary to coordinate the processing of each slice to determine the optimal compression ratio. Video compression exploits the redundancy of moving images, but this redundancy can vary significantly depending on the image content, and even exhibit extreme spatial deviations within a single image.
When encoding multiple slices, the image redundancy contained in each slice can vary significantly. Generally speaking, when image redundancy is high, image quality degradation is not noticeable even if a higher compression ratio reduces the amount of data. However, when redundancy is low, image quality degradation may be noticeable unless a lower compression ratio is used to increase the amount of data.
Therefore, when encoding multiple slices, the amount of compressed data must be adaptively allocated to each slice. If this adaptive allocation process is difficult, localized image quality degradation may occur. Adaptive allocation within a single slice can be performed as a series of processes, which offers advantages in image quality control.
NAL unit appearance conditions and metadata processing
Table 1 of the standard lists the NAL unit types related to video elementary streams specified in ISO/IEC 14496-10. For the implementation of End_of_Sequence and End_of_stream, it is necessary to note that if the endpoint changes during stream editing, these data need to be regenerated.
In the SEI NAL unit, AVC/H.264 stream attribute information such as unregistered user data specified by individual users can be recorded. However, if this data is only recorded in the SEI NAL unit, this information cannot be extracted unless all AVC/H.264 streams are decoded.
The standard recommends placing attribute information (such as shooting date and time information) in MXF metadata instead of recording it in the SEI NAL unit. This can reduce the burden on playback devices and editing applications and improve operational responsiveness.
Implementation Recommendations and Best Practices
Based on the technical requirements of IEC TS 63499:2024, the following implementation recommendations are provided to broadcasters:
System Architecture Design
When designing and implementing IMF Application 6 workflows, the overall system architecture should be considered. Factors such as the file storage system, network transmission bandwidth, and processing node performance all need to be coordinated with the encoding parameter selection.
Encoding Parameter Optimization
Given the characteristics of UHDTV content, it is recommended to use the High 4:2:2 profile for 3840×2160 image format. When selecting the number of slices, a balance should be struck between the advantages of parallel processing and image quality control requirements. 8-12 slices are generally recommended.
Metadata Management Strategy
Establish a comprehensive metadata management strategy, storing technical metadata and descriptive metadata in appropriate locations. Technical parameters should be stored in the SPS/PPS, while production metadata should be stored in the MXF header.
Quality Control Process
Establishing an IMF-based quality control process, leveraging the flexibility of CPL to implement partial rendering and quality inspection, significantly improves the efficiency of post-production modifications while ensuring consistency across different versions.
Technological Evolution and Future Outlook
IEC TS 63499:2024 represents a significant advancement in broadcast workflow standardization. With the continuous advancement of technology, further evolution is possible in the following areas:
First, advancements in coding technology may support more efficient video coding standards, such as HEVC/H.265 or VVC/H.266, further reducing bitrates while maintaining the same visual quality.
Second, the development of cloud computing and edge computing will bring new possibilities to IMF workflows, and distributed processing and storage will further improve workflow efficiency.
Finally, the application of artificial intelligence and machine learning technologies will optimize encoding parameter selection and quality control processes, enabling more intelligent content production workflows.
By following the guidance provided by IEC TS 63499:2024, broadcasters can establish efficient, standardized workflows and better address the technical challenges of the UHD era.
IEC TS 63499:2024 Referenced Document
- ISO/IEC 14496-10:2020 Information technology -- Coding of audio-visual objects-- Part 10:Advanced video coding
- SMPTE ST 2067-60:2023 ST 2067-60:2023 - SMPTE Standard - Interoperable Master Format — Application #6 UHDTV Program Workflow (AVC)
- SMPTE ST 377-1:2019 ST 377-1:2019 - SMPTE Standard - Material Exchange Format (MXF) — File Format Specification
- SMPTE ST 381-3:2017 ST 381-3:2017 - SMPTE Standard - Material Exchange Format—Mapping AVC Streams into the MXF Generic Container
IEC TS 63499:2024 history
- 2024 IEC TS 63499:2024 Encoding guidelines for interoperable master format - Application #6
