Overview
ISO/IEC 11172-1:1993/Cor 2:1999 is Technical Corrigendum 2 to the MPEG-1 Systems standard. It publishes corrections and clarifications to the original Part 1 text for coding moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s. The corrigendum updates key algorithmic formulas, timing relationships, sample stream examples and many subclause headings to remove ambiguity for implementers of MPEG-1 systems, multiplexing and decoding workflows.
Key Topics
- Corrections to multiplexing calculations - the corrigendum amends the formula in A.5.4 that relates video/audio data rates, packet headers and packet data sizing used in stream rate computations.
- System Clock Reference (SCR) - explicit timing corrections: the SCR2 field is specified to occur 6 184 bytes after the first pack, with the corrected relation:
SCR2 = SCR1 + 6 184 * 90 000 / 176 059
- Sample data stream - A.5.9 replaces the sample stream table, showing corrected pack and packet sequences, start codes (e.g., 000001BA for pack_start_code), system header (000001BB), packet_start_code_prefix (000001), stream IDs (video E3, audio C0), packet_length, stuffing bytes, and PTS/DTS markers.
- Clarified function and section names - several subclauses were renamed or split for clarity, including definitions for bytealigned, nextbits, next_start_code, and structured subsections on System Clock Frequency, Input to the System Target Decoder, Buffering, Decoding, Presentation, Pack, System Header, Packet Rate, and System Target Decoder buffer size.
- Timing and timestamp fields - corrected presentation (PTS) and decoding (DTS) examples and placement within packet structures.
Applications and Who Uses This Standard
- Implementers of MPEG-1 encoders, multiplexers, decoders and firmware/software that handle low-bitrate digital storage media (around 1.5 Mbit/s).
- Developers and testers ensuring interoperability between stream producers and System Target Decoders (STDs).
- Engineers validating correct handling of SCR, PTS/DTS, packet structure, stuffing and system headers in hardware (ASIC/FPGA) and software players.
- Archivists and media system designers working with legacy MPEG-1 streams on constrained storage/media.
Related Standards
- ISO/IEC 11172 series (MPEG-1): Part 2 (Video) and Part 3 (Audio) - complements this Systems corrigendum.
- Later standards in the MPEG family expand or refine system and compression techniques (e.g., MPEG-2), for broader or higher-bitrate applications.
Keywords: ISO/IEC 11172-1, MPEG-1 Systems, Technical Corrigendum 2, SCR2, PTS DTS, packet_start_code, multiplexing, system target decoder, buffering, 1.5 Mbit/s.