AN2014-19 4K Change-over.pdf

4K Change-over

An Axon application note

4K integrity checking probe with 2x1 switch-over function

Copyright Š 2014 Axon Digital Design b.v.

All right reserved No part of this document may be reproduced in any form without the permission of Axon Digital Design b.v.

4K INTEGRITY PROBE WITH 2X1 SWITCH-OVER

Introduction 4K Signal Transport

Customer Requirements

There are currently several methods of transporting Ultra High definition (UHD), otherwise known as 4K signals, within a production environment. This AppNote focuses solely on those using 4 separate, but related, 3G (2,970Gb/s) SDI streams.

A major, UK based, signal distribution organization required the integration of 2 x1 change-over functionality in to its 4K distribution system. The originators of the signal were to provide a main and reserve 4K feed, presented as 4 x 3G SDI signals and the customer required an autonomous system to detect signal loss or errors on any of the four streams and change-over to the other source, but only if the other source was not also showing errors. The change-over should not generate any audio noise and it should be possible to configure the probing functions for each quadrant's signal to match the expected content, i.e. only the Top-Left (TL) quadrant probe should monitor the presence of audio.

Each stream carries 1 quadrant of a subdivided 3840 x 2160 pixel image, by convention the Top-Left (TL) stream additionally carries up to 16-channels of audio and also any data to be contained within the signal.

The use of 3G-SDI allows existing broadcast infrastructure to be utilized for UHD production however special care has to be taken to ensure that the signal carrying each quadrant passes through any routing or processing without losing synchronicity with the other quadrants.

Particular care should be taken if audio is Dolby processed or Watermarked as these will involve considerable delay of the TL signal and therefore compensating delay needs to be added to the other three quadrants.

Input A (TL) Input B (TL) Input A (TR) Input B (TR) Input A (BL) Input B (BL) Input A (BR) Input B (BR)

All four change-over operations where to take place within the same frame and there was to be the facility for manual control of the change-over so the switch could also be used if maintenance was required on either input path.

Ideally the switch would have multiple outputs and no external control systems were to be used.

2x1 Switch & Probe 2x1 Switch & Probe 2x1 Switch & Probe 2x1 Switch & Probe

Output (TL)

Output (TR)

Output (BL)

Output (BR)

Figure 1: Customer Requirements functional block diagram

4K INTEGRITY PROBE WITH 2X1 SWITCH-OVER

Synapse Solution GIX110 Module

CRC errors and loss of subtitling. The module also has frame synchronization for each input and silent audio switching providing a seamless switch between two signals. Figure 2 shows the block diagram for the GIX110, as can be seen the module has other advanced features including internal test signal generation, audio track shuffling and a 4 x 2 input router.

Many Synapse modules have monitoring functionality however within the range there are a number specifically designed to monitor a wide range of signal parameters and, depending on user configuration, automatically switch to an alternative source. One such card is the 3G capable GIX110, which provides probing for two 3G SDI streams and is able to monitor such parameters as audio silence, video loss or freeze,

Combining four GIX110 cards provides the basis for a 4K probing and 2 x1 change-over system.

GIX-HIX100–110

3Gb/s, HD, SD IN 1

3Gb/s, HD, SD IN 2

3Gb/s, HD, SD IN 3

3Gb/s, HD, SD IN 4

[QUAD SPEED AUDIO BUS]

MAIN

EQ

EQ

‘110’ MODELS ONLY

3Gb/s, HD, SD OUT B1 2X1

FRAME-SYNC TEST PATTERN AUTOPHASER & OFFSET DELAY

EQ

MAIN VIDEO PROBE

3Gb/s, HD, SD OUT B2

MAIN AUDIO PROBE

BACKUP VIDEO PROBE

3Gb/s. HD, SD OUT A2

2X2 BACKUP SWITCH

BACKUP

EQ

3Gb/s, HD, SD OUT A1

16 CHANNEL EMBEDDER [BYPASS]

FRAME-SYNC TEST PATTERN AUTOPHASER & OFFSET DELAY

PROBE LOGIC

16 CH

BACKUP AUDIO PROBE

16 CHANNEL DE-EMBEDDING

TRACKING DELAY

16 CHANNEL DE-EMBEDDING

TRACKING DELAY

BY-PASS 16 CHANNEL V-FADE CLEAN SWITCH

GPI-IN (MANUAL SW)

RACK CONTROLLER 1

REFERENCE INPUTS 2

‘110’ MODELS ONLY

TDM MUX 16CH OUT

QUAD SPEED MULTIPLEXING AUDIO BUS

TDM DE-MUX

GPI/O OR TRIGGER LOGIC

GPI OUT (STATUS)

16CH IN TO ADD-ON

PLL

FROM ADD-ON

µP [LINUX]

INTERNAL SYNAPSE BUS

Figure 2: GIX110 Block Diagram Practical Application A complete, autonomous, 4K change-over system comprises 4 x GIX110 and a GPI16 module, all located in the same frame.

Each GIX110 module is configured to initiate a changeover (set to A + B or Switch) on some or all of Video configuration tab with switching triggered by carrier loss, video freeze, black and by CRC errors

the possible probing triggers and these can be different for each quadrant's module. Figure 3 (next page) shows a typical configuration for the TL module, the other modules would probably be configured in a similar manner for the video triggers but set to ignore any audio triggers.

Audio Configuration tab, switching triggered by audio loss on channels 1/8 and Dolby channel

Figure 3: GIX110 Probe Configuration

4K INTEGRITY PROBE WITH 2X1 SWITCH-OVER Control In single-stream SDI environments (SD, HD or 3G) the card may be configured to detect video or audio errors within the stream and switch to the other input. The module works autonomously without the requirement for an additional control and monitoring application. So a basic system could be formed by simply utilizing four modules.

In this application the customer requires that if one of the four streams, making up a UHD signal, develops an error all streams should switch from the faulty input to the other at the same time, so some form of communication between modules is required.

However the customer did not what to use an external application, such as Axon’s Cerebrum, to moderate information from the four probing modules and issue switching instructions accordingly.

transmitting one of two codes to all other modules in a frame. The first code is the On code and the Off code is always 128(dec) higher.

The GIX110 uses Generic Event_5 to indicate the overall error status of Probe A and Generic Event_6 for Probe B. If the Probe A is in-error a 62(dec) code is transmitted and when Probe A returns to OK a 190(dec) (62 + 128) code is sent. Probe B will send 63(dec) and 191(dec) codes respectively.

The GPI16 module can detect changes in codes being sent from one or all cards in a frame and close, or open, a GPO relay accordingly. Although the Event messages are transitory the GPI16 can latch the output relay and here it is used as a memory store holding the current Event status.

To satisfy the customer's requirements to produce a simple and reliable 4K change-over switch the solution utilizes the "Events" messaging feature on the module coupled with a Synapse GPI16 general purpose interface card Card Generated Messages: "Events" An Event is a special message generated on the module asynchronously. The goal of an Event is to inform the local system about a changed condition on the module such as a status change, for instance a message could be generated if there is a loss of external reference and another when it returns. These messages are only used within the frame housing the module, communication to external devices uses either the Axon Control Protocol (ACP) or SNMP (if fitted).

The GIX110 generates Event messages for such occurrences as change of Input, Freeze and Black status, further details can be found in the GIX100/110 manual.

In addition to Event messages being generated for changes in specific conditions, more generic messages are also generated by the GIX110 when anything that has been configured to be an error for each probing channel changes. It is these "Probe A (or B) Total sum of errors" Event messages that will be used to trigger all of the modules to change-over at the same time.

Management of Events The GPI16 module is a Synapse card that contains 10 General Purpose Interface (GPI) Inputs, termed GPI and 16 GPI Outputs, termed GPO and it is these GPO that are used in the management of the Event messages from the GIX110 modules.

Each Event message has two states “On” and “Off” e.g. a Probing channel can be “OK” or “In-error” and the module communicates the status of each Event by

GPI16 Control tab showing the first 4 GPO configured to respond to Event messages 62 or 63 originating from any card within the frame.

Configuring a GPO to respond to 62 also means it will respond to 62+128 = 190. Note the relay has been set to default to the Off position on power-up.

Figure 4: GPI16 Control Configuration (Screen Grab from Cortex configuration appliaction)

4K INTEGRITY PROBE WITH 2X1 SWITCH-OVER

GIX110 Classic View tab shows the card configuration in a raw form, it also provides access to the Event message configuration in the Alarm section. The switching system relies on Tags 62 and 63 being sent to the GPI16 card, to enable these select the drop-down list next to the relevant Tag item and select “On”.

Figure 5: GIX110 Alarm Configuration

GIX110 Input A (TL) Input B (TL)

SDI 1

Probe

SDI 2 SDI 3 SDI 4 GPI

GIX110 SDI

Output (TL)

SDI Frame Sync 2x1 Switch

Input A (TR) Input B (TR)

SDI 1

SDI

SDI 3

SDI

SDI 4 GPI

Audio Shuffle

GIX110 Input A (BL) Input B (BL)

SDI 1 SDI 2 SDI 3 SDI 4

GPI16 GPI 1 GPI 2

GPI Logic

GPI GPO 1

Probe

2x1 Switch Audio Shuffle

SDI

Output (TR)

SDI Frame Sync 2x1 Switch

SDI SDI

Audio Shuffle

GIX110 SDI SDI

Frame Sync

Probe

SDI 2

Output (BL)

Input A (BR) Input B (BR)

SDI 1

Probe

SDI 2

SDI

SDI 3

SDI

SDI 4 GPI

SDI

Output (BR)

SDI Frame Sync 2x1 Switch

SDI SDI

Audio Shuffle

GPO 2

GPI 3

GPO 3

GPI 4

GPO 4

GPI 5

GPO 5

GPI 6

GPO 6

GPI 7

GPO 7

GPI 8

GPO 8

GPI 9

GPO 9

GPI 10

GPO 10 GPO 11 GPO 12 GPO 13 GPO 14 GPO 15 GPO 16 Synapse Bus

Figure 6: System Inter-connection

4K INTEGRITY PROBE WITH 2X1 SWITCH-OVER Each module would have the appropriate video connections made as shown in Figure 6.

To ensure that all modules switch at the same point in time the module that has detects the error must not change-over immediately but wait for the same trigger as the other modules. To achieve this the modules are set to be controlled by the GPI input only, they are also configured to use GPI Mode 2 which uses GPI-1 to switch to Input A and GPI-2 to switch to Input B as shown in Figure 7.

Each Event message controls two GPO relays, the arrangement shown ensures that a change-over will only occur if the other channel is not in an error state.

If any GIX110 module detects an error with a parameter being monitored by probe A (Input A) it will issue an Event message with code 62, this operates GPI-1 and GPI-4. Pin 2 (Select input B) on all GIX110 control connectors is routed to the ganged Pin 8 (Common Ground) via GPI-1 (pins 14 & 2) and GPI-3 (pins 4 & 17). This will select Input B. GPI-3 is control by Event message 63 which is generated when any module's probe B detects an error.

Therefore if any module has already detected an error on Input B, GPI-3 will be open and the system will not issue a "switch to Input B" command.

Once a changeover has occurred the cards will remain in that state until either manually switched or a fault occurs on Input-B.

Figure 7: GIX110 Control Configuration Modules also need to be referenced to an external source of either Color Black or Tri-Level Syncs, if no reference is available the system will still switch if a fault is detected however each quadrant will re-sync to the new video source in a different time period to the others producing obvious on-screen artifacts.

Figure 8 shows the connections and GPI pin-out for the GIX110 module and Figure 9 (next page) shows a suggested wiring diagram to connect the GPI16 module to the four GIX110 modules. Diodes have been indicate to provide DC isolation between the GIX110 modules.

A similar situation would occur if the system was already switched to Input B and error was detected on any module's probe B; a code 63 message would be generated, GPI-2 and GPI-3 would open but the system would only change to Input A if GPI-4 was not operated (closed) indicating there was no fault with any module’s input A. When a relay is operated it will remain latched until another message releases it. The modules will then remain routed to the selected input until an another switching command is issued.

The combination of common reference and common control ensures that each quadrant switches at the same point without any on-screen effects being visible.

Ground GPI Input 3

Audio preset selection (110 only)

Output-B route

A = 0, B = 1 (Active-B status)

Output-A route

A = 0, B = 1 (Active-A status)

Probe-B status

Ok = 0, Error = 1 (video and audio alarms for channel B)

Probe-A status

Ok = 0, Error = 1 (video and audio alarms for channel A)

GPI select Input B GPI select Input A

BNC 1

Input 1

BNC 2

Input 2

BNC 3

Output 1

PIN 8 PIN 7 BNC 4 PIN 6

Output 2

PIN 5 RJ45 PIN 4

GPI I/O

PIN 3 PIN 2

BNC 5

PIN 1

BNC 6

BNC 7

BNC 8

Output 3 Output 4 Input 3 Input 4

Figure 8: GIX110 Connections and GPI Pin-out

4K INTEGRITY PROBE WITH 2X1 SWITCH-OVER

1

GIX110 Control 2

8

1

GIX110 Control 2

8

1

GIX110 Control 2

8

1

GIX110 Control 2

8

GPI16 Configuration Default = Off

Tag = 63

GPI 1

Default = Off

Tag = 62

GPI 2

Default = Off

Tag = 62

GPI 3

Default = Off

Tag = 63

GPI 4 GPI 5 GPI 6 GPI 7 GPI 8

1 14 2 15 3 16 4 17 5 18 6 19 7 20 8 21 9 22 10 23 11 24 12 25 13

Figure 9: 4K Change-over System GPI Wiring