| Full title | SMPTE ST 2110, Professional Media Over Managed IP Networks. AES67, AES standard for audio applications of networks: High-performance streaming audio-over-IP interoperability |
| Publisher | Society of Motion Picture and Television Engineers (SMPTE); Audio Engineering Society (AES) |
| Current editions | ST 2110-10:2022 (system timing); ST 2110-30:2025 (PCM audio); AES67-2023 (printed 18 December 2023) |
| Status | Active. ST 2110 parts are revised individually |
| Timing standards | SMPTE ST 2059-1:2021 and ST 2059-2:2021, based on IEEE Std 1588-2008 |
| Related standards | SMPTE ST 2022-7 (seamless protection switching), IEEE 802.3 |
What it covers
SMPTE ST 2110 defines how professional video, audio and ancillary data travel as separate real-time streams over IP networks inside broadcast and production facilities. Each essence is its own RTP stream, and all streams are tied to a common reference clock so they can be time-aligned at the receiver.
The suite builds on the work of VSF TR03 and TR04 and of AES67. Each production element is carried separately over IP, so video, audio and data can be switched separately.
AES67 is an interoperability standard for high-performance audio over IP. It targets professional audio at 16-bit, 44.1 kHz and higher with latency under 10 ms, on local area networks and enterprise-scale networks. It covers synchronisation, media clock identification, network transport, encoding and streaming, session description and connection management.
ST 2110 parts
| Document | Subject | Latest version |
|---|---|---|
| ST 2110-10 | System timing and definitions | 2022 |
| ST 2110-20 | Uncompressed active video | 2022 |
| ST 2110-21 | Traffic shaping and delivery timing for video | 2022 |
| ST 2110-22 | Constant bit-rate compressed video | 2022 |
| ST 2110-30 | PCM digital audio | 2025 |
| ST 2110-31 | AES3 transparent transport | 2022 |
| ST 2110-40 | SMPTE ST 291-1 ancillary data | 2023 |
| ST 2110-41 | Fast metadata framework | 2026 |
| ST 2110-43 | Timed Text Markup Language for captions and subtitles | 2021 |
SMPTE also publishes OV 2110-0 (roadmap for the suite, 2018) and recommended practices RP 2110-23 (single video essence over multiple ST 2110-20 streams), RP 2110-24 (standard definition video) and RP 2110-25 (measurement practices).
Timing
ST 2110-10 requires all devices to support a common reference clock delivered by IEEE Std 1588-2008 Precision Time Protocol (PTP), at any message rate allowed by the SMPTE ST 2059-2 profile. If no common clock is available, devices can signal another clock source.
| Document | Content |
|---|---|
| SMPTE ST 2059-1:2021 | Defines the SMPTE Epoch and the alignment of real-time signals to it |
| SMPTE ST 2059-2:2021 | SMPTE profile of IEEE 1588-2008 PTP for professional broadcast, with parameters, defaults and permitted ranges |
| AES-R16-2016 | AES technical report on parameter compatibility between the AES67 media profile and ST 2059-2 |
Where audio must be exchanged with AES67 devices, ST 2110-10 says PTP message rates should meet the limits of both the ST 2059-2 profile and the AES67 media profile.
ST 2110-30 and AES67
ST 2110-30 carries PCM audio by reference to AES67, with constraints. Streams must conform to AES67, but receivers need not support SIP or any other AES67 connection management method. All devices must support 48 kHz. Support for 44.1 kHz or 96 kHz is recommended. Compressed and non-PCM audio are out of scope. ST 2110-31 carries AES3 signals transparently, including AES3 signals that carry non-PCM data.
The 2025 revision explicitly defines conformance levels for both senders and receivers. Every sender and receiver must meet Level A.
| Sender level | Sampling rate | Packet time | Channels |
|---|---|---|---|
| A | 48 kHz | 1000 µs | 1 to 8 |
| AX | 96 kHz | 1000 µs | 1 to 4 |
| B | 48 kHz | 125 µs | 1 to 8 |
| BX | 96 kHz | 125 µs | 1 to 8 |
| C | 48 kHz | 125 µs | 9 to 64 |
| CX | 96 kHz | 125 µs | 9 to 32 |
AES67-2023 replaced AES67-2018. It added a protocol implementation conformance statement (Annex G), a sender keep-alive recommendation, MTU requirements when RTP header extensions are used, corrected SDP examples and a corrected PTP domainNumber range.
Network requirements stated in ST 2110-10
- Network interfaces must support IPv4. IPv6 support is recommended.
- Streams use RTP over UDP. Senders and receivers must support IPv4 multicast with IGMP signalling (IETF RFC 3376), and IPv4 unicast.
- The Standard UDP Size Limit is 1460 octets. An optional Extended UDP Size Limit of 8960 octets may be used where the essence standard allows it. Senders must not send fragmented IP packets.
- Redundant streams use SMPTE ST 2022-7, and two or more networks in parallel may be used.
- ST 2110-21 defines narrow (Type N), narrow linear (Type NL) and wide (Type W) video senders, and a network compatibility model intended to suit switches with varied buffer sizes.
What it means for network cabling
The ST 2110 documents set requirements at the IP layer and above. They do not specify an Ethernet physical layer, link speed or cabling. The physical links are standard Ethernet to IEEE 802.3, so cabling is selected and tested to the structured cabling standards for the link speed in use.
- Ask the system designer for the Ethernet link speed at each port. Then choose the cabling class or fibre type that supports that PHY.
- Where ST 2022-7 redundancy is used, expect two separate network paths to each device and plan cabling routes to match.
- Expect the network to carry PTP timing, IGMP multicast and, if used, the extended 8960 octet UDP size. These are switch and configuration matters, not cabling ones.
- The ST 2110 documents set no cable lengths or cabling performance limits.