Clarifying Processing Delays Specific to a Riedel
MediorNet IP System
by Renaud Lavoie, Francois Gagnon, Daniel Tremblay

Introduction
The goal of this white paper is to provide some insight into the delays1 occurring inside the basic blocks of an ST 2110 system. While thisdocument mainly focuses on Riedel products (because not all gateways and processing devices act the same in ST 2110 systems), it also
provides a general rule of thumb for delays in switches and in traditional SDI systems.
In this paper, we address one of the most frequent questions from customers who are still at the beginning of their transition from SDI to
IP: What is the latency in a MediorNet IP ST 2110 system and how does it differ from an SDI system?
To this end, we divide the system into its basic blocks: the encapsulators and de-encapsulators, the switches, the processing devices, andthe encoders and decoders.

1. Basic 2110 Encapsulator Delays
The encapsulator is also referred to as the sender gateway. Encap in NMOS and control systems is composed of the SDI / HDMI input andthe output to the network. Riedel’s MediorNet IP product line is equipped with frame synchronizers and audio sample rate converters(except the J2K encoders, which do not need such functionality as they do not need PTP reference) to synchronize free run signals to the
PTP flow in ST 2110. Of course, the frame synchronizer will add delay for the signal not in sync. For synchronous signals (PTP locked), thisfunction can be disabled to minimize the encapsulator delay (eDelay). The following figure shows the encap blocks:

2110 SDI GATEWAY
Video

SDI

FS

GW
SDI to 2110

Audio

...

...

...

Metadata

eDELAY

Figure 1. ST 2110 SDI encapsulator delays (eDelay) with/without ST 2022-72

Essence

Async eDelay with FS

Sync eDelay without FS

Video

Up to 1 frame½ lines

Audio

Up to 1 frame

1 packet: Dependent of packet time (pTime; max 1msec)

ANC

Up to 1 frame

Mode 1 (M-bit): 1 frame (1 packet per frame)
Mode 2 (MTU mode): Fill MTU (1500 bytes of data)
Mode 3 (Quick): Send packet per ANC (packet time at 10G or 25G)

Table 1. ST 2110 SDI encapsulator delays (eDelay)____________________
Delay and latency are often used interchangeably, but they are not always the same. While there is no universally valid distinction between the two, latency is often associated with the round-trip
time (the time it takes for a packet to be sent plus the time it takes for it to return back). This paper, howver, investigates the different parts that make up the “overall latency” in a system, like thedelays inside the senders or receivers.
2
Only de-encapsulators are affected by 2022-7.
1

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2021-06 | Subject to change without notice. Errors and omissions excepted.

The eDelay depends on the frame synchronizer (FS). Accordingly, the following table is divided into eDelay with and without FS:

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﻿Note on Audio: The audio delay depends on the packet time (pTime). For a 1ms pTime, the delay will match this 1 ms delay + transmission time,
which is neglectable.
Note on ANC: There are different ANC modes in ST 2110 encapsulators.
In Mode 1, also referred to as the M-bit mode, the ANC packets are kept in the encapsulator until the M-bit arrives.
Mode 2 is MTU mode, where packets are filled with ANC before sending. MTU is 1500 bytes per payload. The total MTU is 1526 bytes with the
Ethernet header. Jumbo Frame is not supported in ST2110.
Mode 3 is the quickest mode: each time an ANC in blanking is completed, the packet is sent over the network.
The following image summarizes the 3 modes (the number of ANC packets is arbitrary and does not reflect reality)

MODE 1

MODE 2

Internal
memory pkts
Vblank2
2

3

1
Vblank4

4

Vblank

2

5

H

2

1
3

Vblank1

H

H

3

MemoryunusedVblankVblank1

H

MODE 3

Internal
memory pkts

H

6
6

5

5

H

6

4

3
M-bit = 1 in ST 2110 packets

Figure 2. ANC modes in ST 2110 encapsulators

2. Basic 2110 De-encapsulator Delays
The de-encapsulator is also referred to as the receiver gateway. The De-encapsulator receives an ST 2110 set of flows and provides an
SDI / HDMI output. Riedel MediorNet IP de-encapsulators are equipped with ST 2022-7 buffers for network redundancy (please note that
encapsulators provide ST 2022-7 packet duplication without requiring additional buffer.
Lost, Delayed or
Damaged Packet

3

Video

2

1

IP
Encap
3

2

1

Network Blue
3

2

1

Network Red
3

2

1

HITLESS DESTINATION END POINT (Receiver)
3

1

Buffer
IP
Decap

3

2

1

BufferVideo

Pkt Merge
3

Seamless Failover Switching

Figure 3. ST 2022-7 explained

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12021-06 | Subject to change without notice. Errors and omissions excepted.

SOURCE END POINT (Sender)

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﻿

The buffer produces the biggest part of the delay inside the receiver, but fortunately, it is configurable to be adapted to your needs.
Different types of ST 2022-7 modes are specified as follows:
Class

SBR

HDBR

A

10 ms

10 ms

B

50 ms

50 ms

450 ms

150 ms150 μs150 μsC
D

3

Table 2. ST 2022-7 delay table
The high bit rate (HBR) is defined as a data rate from 270Mbps, HD, 3G up to UHD and more. The SBR is a lower bit rate defined as lower
than 270Mbps.
The following picture represents a de-encapsulator. The table below shows the delay the device will exhibit with and without ST 2022-7.

SMPTE ST 2110

2110 SDI GATEWAY
Video
Buffer2022-7

Audio

2110 to
SDI

SDI

...

...

...

Metadata

dDELAY

Figure 4. ST 2110 SDI de-encapsulator delays (dDelay)

Essence

Sync (dDelay) with 2022-7

Sync (dDelay) without 2022-7

Video

2022-7 D: 150 μs

7 lines HD
14 lines in 3G
56 lines in UHD mode

Audio

Audio is realigned with video 20227 D: 150 μs

Audio is realigned with video.
7 lines HD
14 lines in 3G
56 lines in UHD mode

ANC

Always 1 frame (mode M-bit to
support all 2110 senders)

Always 1 frame (mode M-bit to support all 2110 senders)Table 3. ST 2110 SDI de-encapsulator delays (dDelay)____________________
3

ST 2022-7 Class D with short delays was added for live production, room to room or studio applications.

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2021-06 | Subject to change without notice. Errors and omissions excepted.

As you can see from the following table, in order to support all ST 2110 in the market, the receiver will add 1 frame of delay on the ANC in
M-bit mode.

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﻿

3. A Rule of Thumb for Network Switch Delays
Today’s network switches are more predictable than old ones. The following rule of thumb assumes that the switch is well-configured(IGMP enabled, ports are not oversubscribed, QoS is present or not, no deep buffers active, packet size MTU 1500, cut through config orstore and forward mode, etc.)
With these assumptions, it is fair and realistic to say that the delay per switch is 5 μs. The following image shows a spine-leaf
configuration, but we can assume that any configuration (spine-leaf, monolith core), each switch will have the same 5 μs delay.
The total delay on an encapsulator to an de-encapsulator path is 15 μs: 5μs for the TOR switch connected with the encapsulator + 5 μsfor the core switch + 5 μs for the TOR switch connected with the de-encapsulator.

SPINE SWITCHING+5uS

Ethernet / IP Core Switch (Primary)

Ethernet / IP Core Switch (Secondary)

10/25/40/50/100GE
LEAF SWITCHING

+5uS

+5uS

TOR

TOR

TOR

10/25GE

Figure 5. Switch delays in a spine/leaf architecture

The J2K encoders and decoders described here are the ones used for SDI to J2K compression and J2K to SDI decompression. To calculate
the delay for this type of compression, all you have to do is combine the J2K delay with the ST 2110 delay. Just be sure not to add the ST
2022-7 block twice, as there’s only a single ST 2022-7 delay period present in this path.
The following images show the J2K encoder and J2K decoder without any blocks of automatic repeat request (ARQ). Attached with theimage you can see the delay of the J2K encoders and decoders. In addition, ultra-low latency (ULL) is not enabled in the following delay.

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2021-06 | Subject to change without notice. Errors and omissions excepted.

4. JPEG2000 (J2K) Delays

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﻿

SDI TO J2K GATEWAYJ2K OVER TSVideo

SDI to
Y/C

SDI

J2K
Encoder

Audio

Metadata

eDELAY

Figure 6. J2K encoder delays (eDelay)

Essence(eDelay)A

2 framesB

2 framesC

2 frames

Table 4. J2K encoder (eDelay) with/without ST2022-7
The J2K decoder block is composed of a buffer for ST 2022-7 and network jitter. The buffer delay is either 2022-7 (A, B, C or D, please see
Table 5.) or a manually configured WAN jitter buffer (when 2022-7 is not used). This buffer has a maximum jitter tolerance of 120 ms asrecommended by the ST 2022-2 specification4.
When ARQ is used, the buffer size will be adjusted based on the number of round trips needed to keep the time for retries long enough to
avoid glitches in the essences.

J2K OVER TS

J2K SDI GATEWAY
Video
J2K
decoder
1 frameconstant

Audio

Y/C toSDISDI

Metadata

dDELAY

Figure 7. J2K decoder delays (dDelay)
Note: J2K encode with ULL profile active could reduce the entire eDelay to a minimum of 1/16 video frame processing delay. J2K decoder with ULL
profile active can reduce the dDelay to Network buffer + 1/16 frames processing delay.

____________________
4

Riedel MediorNet JPEG-2000 solutions also support 10ms.

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2021-06 | Subject to change without notice. Errors and omissions excepted.

Buffer2022-7 +WAN jitter
bufferwww.riedel.net

﻿

Essence

Sync (dDelay) with 2022-7

Sync (dDelay) without 2022-7

Video
Audio
ANC

1 frame + buffer size(2022-7A: 1frame + 10ms)(2022-7B: 1frame + 50ms)(2022-7C: 1frame + 450ms)(2022-7D: 1frame + 150μs)

1 frame + buffer size (100µs granularity)

Table 5. J2K decoder (dDelay) with/without ST 2022-7
Note: These delays do not consider wide area networks. Please contact Riedel system consulting to calculate these delays.

5. JPEG-XS Delays
The JPEG-XS encoders and decoders described here are the ones used from SDI to JPEG-XS and vice versa. To calculate the delay for thistype of compression, all you have to do is combine the JPEG-XS delay with the ST 2110 delay. Just be sure not to add the ST 2022-7 block
twice, as there’s only a single ST 2022-7 delay period present in this path.
The following images show the JPEG-XS encoder and JPEG-XS decoder without any blocks of automatic repeat request (ARQ). Attached with
the image you can see the delay of the JPEG-XS encoders and decoders.

JPEG-XSSDI TO JPEG-XS GATEWAY

SDI

...

...

...

...

...

2110-40...

Metadata

2110-22...

2110-30/31

...

Audio

SDI to Y/C...

JPEG-XS

...

Video

eDELAY

Essence

Async (Frame Sync on)

Sync (dDelay) without FSVideo

10 lines + 1 frame

10 lines

Audio

Up to 1 frame

1 packet: dependent of pTime (max 1ms)

ANC

Up to 1 frame

Mode 1 (Mbit): 1 frame (1 packet per frame)
Mode 2 (MTU mode) : Fill MTU (1500 bytes of data)
Mode 3 (Quick): send packet per ANC (packet time at 10G or 25G)

Table 6. JPEG-XS encoder delays (eDelay)

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2021-06 | Subject to change without notice. Errors and omissions excepted.

Figure 8. JPEG-XS encoder delays (eDelay)

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﻿JPEG-XS

JPEG-XS TO SDI GATEWAY
Video

2110-22

...

...

...

...

...

...

...

Buffer 2022-7+ WAN jitter
buffer

2110-30/31

JPEG-XS

Audio

2110-40

Y/C to SDI

SDIMetadata
dDELAY

Figure 9. JPEG-XS decoder delays (dDelay)

Essence

With 2022-7

Without 2022-7

Video

10 lines + 2022-7 delay

10 lines

Audio

Audio is realigned with video 2022-7 delay

Audio is realigned with video. 10 lines

ANC

Always 1 frame (mode M-bit to support all 2110 senders)

Always 1 frame (mode M-bit to support all 2110 senders)Table 7. JPEG-XS decoder delays (dDelay)
Note: These delays do not consider wide area networks. Please contact Riedel system consulting to calculate the delay.

6. 2110 Encapsulator to 2110 De-encapsulator Delays
The following figures give some estimates on delays from ST 2110 encapsulators to ST 2110 de-encapsulators.
Figures 10 and 11 show an encapsulator to de-encapsulator without frame sync (input is already synchronized) with & without ST 2022-7
redundancy (please note that only 1 network is shown). Figures 12 and 13 show an encapsulator to de-encapsulator with frame sync (input
is asynchronous / freerun) with & without ST 2022-7 redundancy (please note that only 1 network is shown).

VIDEO & AUDIO

ANC½ line+5 μs* inlines switches+

HD: 7 lines
3G: 14 lines
4K: 56 lines< 1 frame+

5 μs* inlines switches+

1 frameFigure 10. ST 2110 delay without frame sync and without ST 2022-7 redundancy

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2021-06 | Subject to change without notice. Errors and omissions excepted.

INPUT SYNCHRONIZED

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﻿

INPUT SYNCHRONIZEDVIDEO & AUDIO

ANC½ line+5 μs* inlines switches+

2022-7 bufferfrom 150 μs to 150 ms< 1 frame+

5 μs* Inlines switches+

2022-7 bufferfrom 150 μs to 150 ms

Figure 11. ST 2110 delay without frame sync and with ST 2022-7 redundancy

ASYNCHRONOUS INPUTVIDEO & AUDIO

1 frame+5 μs* inlines switches+

HD: 7 lines
3G: 14 lines
4K: 56 lines

ANC

1 frame+5 μs* inlines switches+

1 frameFigure 12. ST 2110 delay with frame sync and without ST 2022-7 redundancy

VIDEO & AUDIO

1 frame+5 μs* inlines switches+

2022-7 bufferfrom 150 μs to 150 ms

ANC

1 frame+5 μs* Inlines switches+

2022-7 bufferfrom 150 μs to 150 ms

Figure 13. ST 2110 delay with frame sync and with ST 2022-7 redundancy

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2021-06 | Subject to change without notice. Errors and omissions excepted.

ASYNCHRONOUS INPUT

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﻿

7. Audio Delay and Lip Sync
The de-encapsulator, or ST 2110 receiver, realigns the RTP timestamp per essence, but does not directly realign the audio on the video
timestamp. One important aspect is that the base frequency of the timestamp is different in audio and video: 48Khz for ST 2110-30/31 and90Khz for ST 2110-20.
This difference is not impossible to overcome. It does, however, make the process less trivial. More importantly, an ‘automatic’ alignment
makes the audio move in time, which creates pops and glitches! To avoid such problems, you can configure the MediorNet IP receiver
manually to compensate the delay – and therefore the lip sync. After this compensation, the devices will keep this in memory and no more
lip sync errors will be observed.
Please note that having a PTP in ST 2110 does not ensure lip sync, because it is the receiver devices that align the essences.

8. Conclusion
As stated in the introduction, this white paper aimed to shed some light on the various delays inside encapsulators, de-encapsulators, andswitches, and explain the various buffers (ST2022-7 and network buffer) and their impact on delay.
All in all, the video over IP path does not exhibit a large delay compared to traditional routers, and the large delay in the encapsulator(eDelay) is present in the same blocks as in SDI (frame synchronizer). On the de-encapsulator or receiver, the delay is adjustable dependingon the system and the network’s expected delay. For a studio, the redundancy could be minimized to make the dDelay imperceptible.
So you might ask yourself: If I replace my SDI router with an IP system, what’s the delay I should expect? Well, there’s no straightforward
answer to this question, because the delays in IP systems are determined by a range of different factors. Just to name a few: Are your inputs
synchronized with PTP? Are they compressed and have to be decompressed or decoded (and then encapsulated in the network)? How
many switches do your signals have to travel through? There’s no easy equation, no clear-cut rule of thumb, because it all depends on theproperties of your network.
If you are looking for an accurate calculation of the delays in your future system, we recommend you contact a Riedel system consultant,
who will be happy to answer all your questions and help you design the network to suit your needs!

2021-06 | Subject to change without notice. Errors and omissions excepted.

To make a long story short: In a studio with a thoughtfully designed network, the total delay is comparable to traditional SDI.

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