ISO/IEC 23008-1:2023/Amd 1:2025

International
Standard
ISO/IEC 23008-1
Third edition
Information technology — High
2023-01
efficiency coding and media
delivery in heterogeneous
AMENDMENT 1
environments —
2025-05
Part 1:
MPEG media transport (MMT)
AMENDMENT 1: Signalling of adaptive
FEC scheme
Reference number
ISO/IEC 23008-1:2023/Amd. 1:2025(en) © ISO/IEC 2025

ISO/IEC 23008-1:2023/Amd. 1:2025(en)
© ISO/IEC 2025
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© ISO/IEC 2025 – All rights reserved
ii
ISO/IEC 23008-1:2023/Amd. 1:2025(en)
Foreword
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Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
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© ISO/IEC 2025 – All rights reserved
iii
ISO/IEC 23008-1:2023/Amd. 1:2025(en)
Information technology — High efficiency coding and media
delivery in heterogeneous environments —
Part 1:
MPEG media transport (MMT)
AMENDMENT 1: Signalling of adaptive FEC scheme

C.2.4
Add the following new subclause after C.2.3 and before C.3:

C.2.4  Adaptive FEC coding structure
Adaptive FEC specified the structure that can be applied with any FEC code and is specific for protecting a
source packet block which consists of different priorities MMT packets.
The MMTP packets from one MMTP flow are divided into different classes based on the different priorities
defined in the DU header. When Adaptive FEC structure is used, the sequence of original MMTP packets
may be changed according to the class order in generation of source symbols. The highest priority source
symbols are presented before lower priority. Then these symbols are grouped into a source symbol sub-
block and the source sub-symbols can be indexed by the repair FEC payload ID. After the FEC encoding, a
FEC repair symbol block will be generated from the source symbol block combining the different sub-blocks
of symbols.
Figure C.20 shows an example of source symbol block generation for media data with two classes for
Adaptive FEC. The source symbol block can be divided into the source symbol sub-block. The number of
source symbol sub-block can be determined based on the number of the class. The FEC code matrix will be
generated based on the number of source symbols and repair symbols in different sub-blocks.
Figure C.20 — Adaptive FEC coding structure

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-1:2023/Amd. 1:2025(en)
Table C.3
Replace Table C.3 with the following table:
Table C.3 — AL-FEC message
No. of
Syntax Values Mnemonic
bits
AL_FEC ( ){
message_id 16
version
length
message_payload{
fec_flag
1 bslbf
private_fec_flag 1 bslbf
reserved “111111” 6 bslbf
if (fec_flag==1) {
length_of_fec_flow_descriptor
16 uimsbf
fec_flow_descriptor() {
number_of_fec_flows
N1 8 uimbsf
for ( i=0; i fec_flow_id 8 uimbsf
source_flow_id
8 uimbsf
number_of_assets
N2 8 uimbsf
for ( j=0; j packet_id
16 uimbsf
}
fec_coding_structure 4 uimbsf
ssbg_mode
2 uimbsf
ffsrpts_flag
1 bslbf
fec_payload_id_mode
1 bslbf
length_of_repair_symbol
16 uimbsf
if (ssbg_mode == 10) {
num_of_repair_symbol_per_packet 16 uimbsf
num_of_symbol_element_per_source_symbol
16 uimbsf
}
if (fec_coding_structure == 0001) {

repair_flow_id
16 uimbsf
fec_code_id_for_repair_flow 8 uimbsf
if (private_fec_flag == 1) {
private_flag
1 bslbf
pri
...