User's Manual

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Version 1.1 SDT_ARK6_User_Manual_ENG_vATSC Page 196 of 206
A.2 Seamless input switching
SDT ARK6 series supports a seamless input switching algorithm that increases the reliability of the system in a
SFN environment. The developed algorithm is capable of changing input signal source on the basis of MIP
packets within the incoming Transport Stream. The algorithm provides a reserve feed to the apparatus in a SFN
environment in the event that the primary input signal source does not meet anymore the SFN constrains. The
device is designed to manage the redundancy between two different sources in a SFN environment by seamless
switching between them
Both HP and LP streams have two different selected inputs. The two selected input are real-time analyzed under
some presence and validity rules. The inputs that are present and valid are eligible to be sent to output in
dependence on the priority rule set. If only one input is present, then is sent to output without the application of
any validity rule.
The presence of an input is evaluated under the following rules:
 The input is an ASI compliant (CEI EN 80083-9) encoded signal.
 The input transports an MPEG-2 TS (ITU.T 13818-1) with no Synchronization Error (as defined by ETSI
ETR 290).
The validity of an input is evaluated under the following rules:
 The Transport Error flag (as defined by ITU.T 13818-1) does not rise in any packet.
 The timing of reception of each input packet is inside the standard boundaries (as defined by ETSI ETR
290).
 The SFN adaptation of the input TS is guaranteed by the presence of a correct MIP (as defined by ETSI
TR 101 191), guaranteed by a CRC32 algorithm checking.
 The TS data validity is guaranteed by the presence of PAT (as defined by ETSI EN 300 468) correct after a
CRC32 algorithm checking.
 The TS data validity is guaranteed by the presence of PMT (as defined by ETSI EN 300 468) correct after
a CRC32 algorithm checking.
 The total delay applied by the distribution network to the input signal is not higher than the Max Delay
set by the SFN adapter.
 The time window available to deliver the TS to the output is higher than the network margin applied.
When the used input check fails, the device seamlessly switches to the secondary input if present and valid,
otherwise it continue to output the same flow despite of the validity rules check.