The way to guarantee a clean switch

Safe Switch-L 3G is the way to guarantee a clean switch – and protect your output.

It provides clean and intelligent 2 x 2 switching between two 3Gb/s, HD or SD sources containing up to four groups of embedded audio, with the full framestore synchroniser on each input allowing it to correct for any timing difference (big or small) between the two inputs – resulting in no disruption to the output picture when a switch takes place.

Ideal for planned maintenance switches to manually re-route a good signal around broken equipment, it can also be used as an intelligent emergency transmission switch by engineers who do not want to restrict themselves to timed inputs, with the option of selecting from 16 different fault conditions to automatically trigger the switch.

With the ability to deal with any type of timing issues, Safe Switch-L 3G gives you a clean switch that can survive even the most catastrophic failure. It can even lose the reference signal and not affect the output. Your viewers will never know there’s a problem.

Why do you need a clean switch?

Continuity of service is vital and it’s crucial you don’t go off air. This is why Safe Switch-L 3G is ideal for use on the final output stage of a transmission system, before the signal gets to the MPEG encoder.

Typically the main programme path goes through various ‘boxes’ before going into a 2 x 1 switch. The second input of the switch is fed the backup signal – often the same material but gone a more simplified route. If something goes wrong on the main programme path you can switch to backup, but the issue is that there will be a delay because the backup has gone through less ‘boxes’.

This time difference between the main and backup signals upsets the MPEG encoder. With the MPEG encoder only transmitting differences between one frame and the next, the consequence of a sudden jump in timing is that the excessive information generated by the disrupted stream causes the MPEG encoder to reach its bandwidth limit and fall over. One frame glitch on the input to the MPEG encoder could lead to up to 15 frames of corrupted video coming out of it.

To balance the delays between the main and backup feeds you could of course use three boards – a switch and two synchronisers – but Crystal Vision saves you space and money by doing it all on one board: Safe Switch-L 3G.

Safe Switch-L 3G is a 2 x 2 switch and you could use the second output to feed a backup redundant MPEG encoder, or your second output could go a completely different route to the transmitter after the MPEG encoder – such as via a microwave link, with the other feed going via fibre.

Another application could be to switch between the main and backup of a server system. Here the second output could be fed to a preview monitor for monitoring the servers.

You could also use the Safe Switch-L 3G with its input loop-throughs to dynamically bypass an individual piece of equipment – such as a DVE that you don’t want to be in your signal path all the time.

Sometimes you need to switch to backup in non-emergency situations – when one of the ‘boxes’ in the chain needs fixing or updating and you want to ignore the path that the box is in.

For all these applications Safe Switch-L 3G will provide the most robust solution possible.

Switch it manually or automatically

Safe Switch-L 3G can either be switched manually or automatically – making it equally suited to planned maintenance switches or emergency transmission applications.

Manual switching takes place according to the setting of the switch timing control. Automatic switching will occur at the switching point given in SMPTE RP168:2009 when the switch timing is set to ‘Field’ or ‘Frame’, or immediately if triggered by the input missing or input video standard fault conditions.

There’s no underlying preference for either input. Being a symmetrical switch means you can select your preferred input by means of a 2 x 2 routing grid, rather than having pre-assigned main and secondary feeds.

Each of the two inputs can be switched to either or both of the two outputs, with up to two reclocked feeds of each switched signal available.

There are lots of switching options available. For example, Output B can be configured to be the opposite of Output A, making B a preview that will always show what will be transmitted if you change the switch allowing you to easily swap to a good secondary feed. Output B can be requested to be the same as Output A – like a 2 x 1 switch with more outputs.

How to get a really clean switch

With Safe Switch-L 3G you never have to worry about a difference in timing between your main and backup feeds – you are always going to get a clean and seamless switch.

The synchroniser in each input stream will ensure that both inputs to the switch are correctly timed to the external analogue reference so that there is no disruption during a switch. Safe Switch-L 3G synchronises sources between 0 and 1 frame. The synchronisers act as a self-adjusting delay, allowing a clean transition between the two channels even if their relative timing has slipped.

It is easy to compensate for mistimed sources elsewhere in the system by adjusting the output timing relative to the reference through an entire frame using horizontal and vertical settings.

Cross-locking allows a 3Gb/s, HD or SD input to be referenced to either HD tri-level syncs or SD Black and Burst – allowing the convenient use of any existing timing signals.

Loss of reference protection

Loss of reference protection – where Safe Switch-L 3G will change its timing smoothly between the reference and the inputs, keeping the output valid at all times – is an unusual and technically-advanced feature which further extends the board’s primary purpose of protecting the output from any disruption.

In normal operation the output timing is derived from the reference. If the reference is lost, Safe Switch-L 3G will switch to input 1 or (if not available or subsequently lost) input 2 as an alternate clock source, changing to the same sample/line/frame rate as the input without disrupting the output video. If the signal input is genlocked to the reference the output will be unchanged, while if not locked to the reference the output data rate will change smoothly, slowly drifting relative to the reference and remaining in spec at all times.

If the reference returns, the board will gently drift from the input source to line up with the reference over a period of time – again without disrupting the output signal.

Intelligent automatic switching - select from 16 fault conditions

Safe Switch-L 3G constantly checks both of the inputs so that the output of the switch always remains proper and valid.

It can be set to automatically switch away from the user-selected input if it does not meet the set requirements. It extracts information about various parts of the video signal to decide which of the two inputs is better, based on the engineer’s selection of which faults are significant.

The 16 video and audio parameters which can be selected to perform a switch, and which are listed in order of priority, are input missing, input video standard incorrect, EDH missing, EDH full field error, EDH active picture error, line CRC error, audio group 1 missing, audio group 2 missing, audio group 3 missing, audio group 4 missing, active video black, active video frozen (including processed frozen picture detection) and audio silence on any channel in a selected group.

Audio silence level settings can be selected from -48dBFs, -54dBFs, -60dBFs, -66dBFs, -72dBFs, -78dBFs, -84dBFs and -90dBFs.

With some processes – such as video compression or converting to analogue and back – introducing small changes frame-to-frame even if the input picture is frozen, the processed frozen picture detection feature allows Safe Switch-L 3G to intelligently distinguish between this noise and real changes in the picture content – and so correctly flag up an error condition and auto switch.

Further flexibility comes from the option to set a time period of between two and 120 seconds before the video black, video frozen and audio silence parameters trigger a switch.

Safe Switch-L 3G will switch away from an error on the user-selected input only if the other input is free of that fault. If both inputs have different alarms, it will use the most significant alarm to decide which feed to select. It works down the list, checking everything that has been chosen by the engineer as being of interest. As long as it does not find an error on the selected input without a corresponding error on the non-selected input, it stays with the selected input. If it finds such an error it switches to the other input.

Following a switch it can either reselect the main feed automatically (with the option to set a time period for which the signal must be good before switching back) or by user intervention.

Safe Switch-L 3G will additionally report the reference video standard.

Easy to monitor for any faults

In addition to the automatic switching, two fault indications can also be set and assigned to GPIs if desired, allowing very flexible monitoring.

These fault indications are very useful, whatever type of switching you are doing. If Safe Switch-L 3G is set to manual switching, the fault indications will tell you that you should switch. If Safe Switch-L 3G is set to auto switching, the fault indications will inform you of the faults that need fixing – otherwise the board could just switch without you knowing why.

The fault indications each have their own list of chosen parameters which can be different from the auto switch selection. Each fault indication can be assigned to a specific input, to either input, or to only become active if both inputs show a selected fault. For example, you could monitor for audio silence on your main channel and get a separate indication if both channels freeze.

Choose your control - with the most flexible GPIs

The Statesman PC control software can be used to either ignore or create an alarm on any of the features that Safe Switch-L 3G can measure. Up to eight Statesman menu tabs provide status information, configuration of the switching characteristics, video timing adjustments, selection of the auto switch criteria, alarm monitoring and configuration of the GPIs.

Safe Switch-L 3G has exceptional GPIs flexibility – ideal for GPI-focused broadcasters who want to have direct control of the board. The 12 GPIs on the Safe Switch-L 3G are all bi-directional, allowing them to be configured as either GPI inputs or GPI outputs and so giving you real flexibility when setting up buttons and lights for GPI control and monitoring of alarm conditions. All 12 GPIs are available via the 26-way high density D-Type on the rear module, as well as the rear of the frame.

Other control options include board edge switches, an active front panel on the frame, a remote control panel and SNMP.

Frames, rear modules - and relay bypass protection

Safe Switch-L 3G is a space-saving 'double decker' 100mm x 266mm module which can be housed alongside any other products in the standard Crystal Vision frames – available in 4U, 2U, 1U and desk top box sizes. Up to six of Safe Switch-L 3G can fit in a 2U frame.

To access the inputs and outputs, Safe Switch-L 3G is used with the RM63 frame rear module.

The RM63 provides the two inputs, two feeds of output A, two feeds of output B, input and reference loop-throughs, extra GPI connections and an analogue reference connection.

The input loop-throughs make it easy to monitor that the source has successfully reached the Safe Switch-L 3G, while the reference loop-through allows you to loop the analogue reference through a number of boards in a single frame – saving a DA and making cabling easy.

The RM63 rear module includes relay bypass protection on power failure or board removal, giving the system an extra layer of security and preventing signal loss.