ST2110 & AES67 Commonalities & Constraints - Andreas Hildebrand ALC NetworX, Munich
A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Andreas Hildebrand, RAVENNA Technology Evangelist • more than 25 years in the professional audio / broadcasting industry • graduate diploma in computer science • R&D, project & product management experience • member of AES67 TG and ST2110 DG ALC NetworX GmbH, Munich / Germany • established 2008 • R&D center • developing & promoting RAVENNA • Partnerships with > 40 manufacturers RAVENNA • IP media networking technology • designed to meet requirements of professional audio / broadcasting applications • open technology approach, license-free • fully AES67-compliant (built-in) #2
A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110
SDI
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110 (32NF-60 SVIP - Studio Video over IP) Document structure:
• 2110-10: System Timing & Definitions defines transport layer and synchronization (SMPTE2059, clocks, RTP, SDP etc.) • 2110-20: Uncompressed Active Video defines payload format for raw video (RFC4175, RTP, SDP, constraints) • 2110-21: Timing Model for Uncompressed Active Video defines timing model for senders and receivers (traffic shaping requirements)
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110 (32NF-60 SVIP - Studio Video over IP) Document structure:
• 2110-30: PCM Digital Audio defines payload format for linear audio (AES67, constraints) • 2110-31: AES3 Transparent Transport defines payload format for non-linear audio (RAVENNA AM824)
• 2110-40: Ancillary Data defines RTP payload format for SDI ancillary data (new IETF draft) • 2110-50: Interoperation of ST 2022-6 Streams what it says… (VSF TR-04) #5
A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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AES67-2015 Standard for Audio Applications of Networks: High-performance Streaming Audioover-IP Interoperability
AES67 #6
A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
published on September, 11th, 2013
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Scope: •
Interoperability guidelines for professional, low‐latency audio over campus and local area IP networks using existing protocols wherever possible.
•
Excludes:
Non‐IP networking Low‐bandwidth media Data compression Low‐performance WANs and public Internet Video (should provide good basis for follow‐on video project)
Goal: •
Technology providers may choose to implement interoperability as a special mode, or transition to it as their native mode
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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AES67
X
Dante
X
WheatNet
RAVENNA
Livewire
Q-LAN
X
X
IP A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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AES67 – the “O negative” of audio networking ACIP AES67 AES67
AES67
A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
RAVENNA
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AES67 technology components: •
Synchronization: IEEE 1588-2008, default profile (media profile suggested)
•
local media clock generation
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Synchronization & media clocks •
All nodes are running local clocks
•
Local clocks are precisely synchronized to a common wall clock via PTP
•
Media clocks are generated locally from synchronized local clock
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Synchronization & media clocks Master Clock
PTP Slave Clocks (nodes)
Media Clocks
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Synchronization & media clocks •
All nodes are running local clocks
•
Local clocks are precisely synchronized to a common wall clock via PTP
•
Media clocks are generated locally from synchronized local clock
•
Generation of any desired media clock (sample rate) possible
•
Concurrent operation of different media clocks possible
•
Phase accuracy of AES 11 (± 5% of sample period) achievable by deployment of PTP-aware switches (BC or TC)
•
Synchronization across facilities possible by reference to absolute time (TAI)
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Synchronization & media clocks •
3 type of clocks in the system: •
Wall clock - provided by Grandmaster
local copy of the wall clock in each node
•
•
Media clock – derived from the local clock (i.e. 48 kHz for audio, 90 kHz for video)
•
RTP clock – derived from the media clock
Essence data (audio samples or video frames) is related to the media clock upon intake - essentially receiving a generation “time stamp” with respect to the media clock
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Synchronization & media clocks
Wall clock PTP
(PTP Grandmaster)
(copy)
• Relations T and R are established on node start-up • Relation S is established on stream start-up • S may be random to defeat cryptotext attacks • This offset will be constant throughout the stream’s lifetime
(copy)
Sender
Receiver
Local clock
T
PTP
Local clock
Stream clock
S
R SDP
Media clock
Media clock
Stream data
• The offset will be conveyed via SDP (a=mediaclk:direct=<offset>) – “0” in ST2110 # 15
A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Synchronization & media clocks •
3 type of clocks in the system: •
Wall clock - provided by Grandmaster •
A local copy of the wall clock in each node
•
Media clock – derived from local clock (i.e. 48 kHz for audio, 90 kHz for video)
•
RTP clock – derived from the media clock
•
Essence data (audio samples or video frames) is related to the media clock upon intake (essentially receiving a generation “time stamp” with respect to the wall clock)
•
Fixed / determinable latency by configuring a suitable link offset (“playout delay”)
•
Inter-stream alignment by comparing and relating the time stamps of individual essence data
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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AES67 technology components: •
Synchronization: IEEE 1588-2008, default profile (media profile suggested)
•
local media clock generation
•
Network: IPv4 (IPv6), unicast / multicast & IGMPv2
•
Transport: RTP/AVP (RFC 3550 & 3551) / UDP / IP
•
Encoding: 16 / 24 bit linear, 48 (44.1 / 96) kHz, channel count: 1..8
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Packet Setup: 48 samples (6 / 12 / 16 / 192), max. payload size: 1440 bytes
•
Quality of service: DiffServ w/ 3 suggested traffic classes (DSCP)
•
Connection management: SDP, IGMP (multicast), SIP (unicast)
•
Discovery: excluded, but several possibilities mentioned (i.e. ZeroConf, SAP and others)
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110 (32NF-60 SVIP - Studio Video over IP) Constraints of 2110-10 & -30 w/ respect to AES67 - Synchronisation & Timing -
• PTP: support of SMPTE 2059-2 required message rate according to AES-R16-2016 (AES67 PTP Media profile) defaultDS.slaveOnly=true for devices not capable of entering PTP master state a=ts-refclk:ptp=traceable and a=tsrefclkts-refclk:localmac=<mac_addr> allowed
• RTP clock: offset= 0 w/ respect to media clock / network clock a=mediaclk:direct=0
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110 (32NF-60 SVIP - Studio Video over IP) Constraints of 2110-10 & -30 w/ respect to AES67 - Protocols -
• Support of RTCP not required (but must be tolerated) • Support of SIP (or any other connection management protocol) not required • Redundancy: SMPTE 2022-7 no identical IP source and destination addresses • Optional channel assignment map (SDP) a=fmtp:<payload type> channel-order=<convention>.<order> Example: a=fmtp:101 channel-order=SMPTE2110.(51,ST)
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110 (32NF-60 SVIP - Studio Video over IP) Constraints of 2110-30 w/ respect to AES67:
• 4 conformance levels: Level
Supported by the Receiver
A
Reception of 48 kHz streams with 1 to 8 audio channels at packet times of 1 ms
B
Level A + 1 to 8 channels at packet times of 125 µs
C
Level A + 1 to 64 channels at packet times of 125 µs
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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SMPTE 2110 (32NF-60 SVIP - Studio Video over IP) Constraints of 2110-30 w/ respect to AES67:
â&#x20AC;˘ 4 conformance levels: Level
Supported by the Receiver
D
Level C + Reception of 96 kHz streams with 1 to 4 channels at packet times of 1 ms and 1 to 32 channels at packet times of 125 Âľs
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A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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Contact information:
Andreas Hildebrand Technology Evangelist ravenna@alcnetworx.de
ALC NetworX GmbH Am Loferfeld 58 81249 Munich Germany
www.ravenna-network.com A. Hildebrand: ST2110 & AES67 - Commonalities & Constraints
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