Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
  • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
  • H04N21/643—Communication protocols
  • H04N21/64322—IP
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
  • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
  • H04N21/235—Processing of additional data, e.g. scrambling of additional data or processing content descriptors
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
  • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
  • H04N21/242—Synchronisation processes, e.g. processing of PCR [Programme Clock References]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
  • H04N21/4302—Content synchronisation processes, e.g. decoder synchronisation
  • H04N21/4305—Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
  • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
  • H04N21/435—Processing of additional data, e.g. decrypting of additional data, reconstructing software from modules extracted from the transport stream
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
  • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
  • H04N21/633—Control signals issued by server directed to the network components or client
  • H04N21/6332—Control signals issued by server directed to the network components or client directed to client

Definitions

• the present invention relates to the field of communication networks.
• the present invention relates more particularly to a transmitting device and to a receiving device for the secure transmission of counter values in the context of the transmission of a synchronization signal, for example of the "Genlock” type (synchronization lock), in a packet-switched network, for example of the IP ("Internet Protocol”) type.
• a synchronization signal for example of the "Genlock” type (synchronization lock)
• IP Internet Protocol
• Transmitting a Genlock signal into an IP network is an important step in converting video studios to IP networks as a single infrastructure.
• the principle consists of driving a counter by the genlock signal to be transmitted. This counter is sampled regularly. The performance of the system is based mainly on the regularity of the sampling mechanism.
• the sampled value is transmitted over the IP network by conventional means.
• the samples are taken into account on a regular basis (same times as the sampling on the receiving side) by the phase lock loop (PLL), which regulates its internal frequency so that the difference between the received sample and its internal counter is zero.
• PLL phase lock loop
• the prior art discloses, by the European patent application EP 0 624 983 (Thomson), a synchronization arrangement for a compressed video signal.
• This European patent application describes an apparatus for developing the synchronization of an intermediate layer of a signal such as the transport or multiplex layer of a multilayer compressed video signal.
• This apparatus comprises on the encoding side, means for including a time descriptor reference, such as a counter value of a modulo counter K, and means for providing a differential time descriptor which can be updated by the transit times of the respective (multiplexing) circuits when the signal passes through these circuits.
• a counter responds according to a controlled receiver clock signal and the value of this counter is sampled at the arrival of the temporal descriptors contained in the transport layer.
• the temporal descriptors and the differential temporal descriptors are extracted from the signal and combined to form a corrected temporal descriptor.
• the differences in the successive sampled counter values of the receiver counter are compared with the differences in the corresponding successive corrected time descriptors to provide a signal for controlling the receiver clock signal.
• the invention of this European patent application of the prior art falls within the framework of broadcast networks with constant transmission rate. Sampling of local counters is done at the moment of reception of the packets containing the samples of the master counter.
• the purpose of this prior invention is to provide corrective information to restore a fair value of the sample transmitted from a master counter through a link that operates but is degraded by transmission jitter. Presentation of the invention
• the present invention is in the context of a packet-switched network, for example of the IP type, in which the transmission time is not constant.
• the video stream, of which the present invention proposes to transport the synchronization signal is not supposed to be at constant bit rate, nor to be linked by a multiplexing system to the information relating to the transmission of the synchronization signal.
• the synchronization information uses its own IP packets: two streams of data, video and synchronization, independent, from the point of view of the transmission network, are present.
• the present invention assumes that a synchronous signal is available on all the stations, generated by another time base, synchronized by another independent system, based for example on the IEC61588 standard, and that it is during the occurrence of this signal that the samples are generated or taken into account, and not at the time of receiving or transmitting packets that are not important in the context of the present invention.
• the technical problem that the present invention proposes to solve is to allow a receiving station to continue to operate, even in degraded mode, while the link through the network is completely interrupted.
• the present invention relates, according to a first aspect, to a device capable of transmitting packets in a packet communication network comprising at least two stations, comprising means for: receiving a signal; driving a counter using said signal; characterized in that it comprises: sampling said counter every period T ech , where T ech is issued from a synchronized time base on all the stations of said network; calculating an increment value predicting at least one next sampled counter value; transmit sampled values and increment values associatedly in packets.
• said signal is of Genlock type (synchronization lock).
• the increment value is 135,000
• the sampling period is 5 ms
• the counter clock, driven by the Genlock signal is 27 MHz.
• the present invention relates to a device able to receive packets in a packet communication network comprising at least two stations, characterized in that it comprises: a phase-locked loop; and means for: receiving packets containing samples of said network, said samples from sampled data all periods T ech , where T ech is from a synchronized time base on all stations of said network and said samples being associated increment values predicting at least one sample; calculate, in the event of a packet reception interruption, a prediction of a sample that should have been received, by adding an increment value to a received sample value.
• the synchronized time base on all the stations of the network is IEC61588 type.
• said communication network is of IP (Internet Protocol) type.
• the principle of genlock signal transmission is based on regular sampling of the counter. Regular sampling means that the time period between two samplings must remain exactly the same. Since the counter being sampled is supposed to be stable because it is locked to the genlock signal to be transmitted, the increment between the two sampled values must remain the same once the system is stabilized.
• the increment value between a sampled value and the next sampled value may change slightly. This is due to the imprecision of the different clocks of the system: the clock of the counter driven by the Genlock signal (video counter in Figure) and the system clock (or network clock in Figure) that calculates the sampling time period. For example, assuming that the sampling period is 5 ms and the clock of the genlock-driven counter is 27 MHz, the increment value should be 135,000 precisely. Due to the relative accuracy of the clocks, the value may be slightly different (135 008 in the case of 30 ppm clocks).
• the exact increment value can be reached after several sampling periods. It can also evolve over time due to clock frequency drift. The speed for this is very low (typically 75 mHz / s).
• the transmitting part which is in charge of sampling the counter driven by the signal
• Genlock (video counter in Figure) and the transmission of the sampled value, can also calculate a precise increment and transmit it.
• the transmission part will transmit an increment value with the sampled value. This increment value is recalculated with each sample. This can evolve to follow the clock drift based on frequency characteristics of the genlock signal (maximum drift of 75 mHz / s). Faster drift can be filtered.
• the receiving part will memorize the increment value each time it receives a new sampled value, just as it will memorize the sampled value.
• the PLL calculates a prediction of the value that should have been received. It must add the increment value to the last sampled value received.
• the PLL can do this as long as no new sampled value has been received. It must memorize the calculated sampled value and use it as if it were the last value received next time.
• the mechanism will ensure that the PLL frequency remains stable and that the recalculated counter does not derive too much from the value it should have.
• the PLL will take into account the new value received and will evolve to compensate for the difference.
• the frequency characteristics of the PLL will ensure that the delivered signal does not drift too fast and that it respects the genlock signal constraints.
• the single figure illustrates the transmitter and receiver devices according to the present invention.
• the invention is described in the foregoing by way of example. It is understood that the skilled person is able to realize different variants of the invention without departing from the scope of the patent.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Synchronisation In Digital Transmission Systems (AREA)
• Data Exchanges In Wide-Area Networks (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=37546683

Family Applications (1)

Country Status (5)

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Family Cites Families (10)

• 2006
  • 2006-03-13 FR FR0650838A patent/FR2898454A1/fr active Pending
• 2007
  • 2007-03-13 EP EP07731735A patent/EP1994766A2/de not_active Withdrawn
  • 2007-03-13 WO PCT/FR2007/050919 patent/WO2007104892A2/fr not_active Ceased
  • 2007-03-13 US US12/225,016 patent/US8218577B2/en not_active Expired - Fee Related
  • 2007-03-13 JP JP2008558867A patent/JP4971374B2/ja not_active Expired - Fee Related

Non-Patent Citations (1)

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