WO2009037365A1

WO2009037365A1 - Remultiplexer system and method for mpeg transport flows

Info

Publication number: WO2009037365A1
Application number: PCT/ES2007/000528
Authority: WO
Inventors: Luis Villa Sanz
Original assignee: Terminales De Telecomunicaciones Terrestre, S.L.
Priority date: 2007-09-19
Filing date: 2007-09-19
Publication date: 2009-03-26

Abstract

The subject of the present invention is a system and a method for assigning the content of a broadband transport network to a narrowband access network by implementing intelligent multiplexing of programs under demand in real-time to access network level.

Description

MPEG transport stream remultiplexer system and method

OBJECT OF THE INVENTION

The present invention, system and method of remultiplexer of MPEG transport flows, refers to a system and method that allows multiplexing a number of transport flows at the entrance of a multiplexer system into a smaller number of transport flows at the exit of the Real-time multiplexer on demand of the user. This multiplexing results in a bandwidth less than the output of the remultiplexer system.

The present invention is encompassed within the field of telecommunications, especially that comprising the transport of video carriers through heterogeneous networks.

STATE OF THE TECHNIQUE

A digital television and / or radio broadcast signal is the result of combining multiple streams that come from different sources. Each of these flows is in baseband and will be modulated by a carrier that will be transmitted through a transport network.

At present there are different video transmission standards depending on the geographical location in which the transmission will take place. For example, in Europe, Africa, Asia and South America, the DVB standard (Digital Video Broadcasting, Digital Video Broadcasting) is implemented, however in Canada, Mexico and the United States the ATSC standard (Advanced Television Systems Committee, Committee for Systems) has been defined Advanced Television) while in Japan the ISDB standard (Integrated Services Digital Broadcasting, Digital Transmission of Integrated Services) is defined.

Each standard specifies the channel coding and modulation schemes for the transmission medium in question, but in all cases the source coding is an adaptation of the audio coding standards, data and video defined by the Moving Picture Experts Group (MPEG).

Therefore the MPEG-x coding standards, those defined by the MPEG group; They are used in conjunction with digital broadcasting standards to stream digital programs.

The MPEG-x standards were developed to be independent of the specific network through which the signals are transported, providing an interoperability point in heterogeneous network environments. However, this causes that even when the bandwidth of the signal is not a problem in transport networks, it can cause saturation of the access networks.

Therefore, since the composite broadcasting signal must be distributed across various types of networks, with bandwidth restrictions, it will be necessary that the original broadcasting signal be remultiplexed into a new signal to adapt to such restrictions in the bandwidth.

It is therefore an object of the present invention to assign the content of a broadband transport network to a narrowband access network by implementing intelligent multiplexing of programs on demand in real time at the access network level.

A transmission of this type, where the content of programs is offered selectively according to the demand of the users, can be easily implemented in IP networks. In this type of networks, the information packets include a destination address field so that any node of the network can route the requested flow to a specific user.

A set of users who demand the same information, commonly called multicast group or multicast group, causes the header to send in response to that demand from the multicast group, a single data stream with a multicast destination address. This flow is referred to most of the network nodes but is replicated only when necessary (when users cannot be reached using a single route). An example of this is the DSLAM IP multiplexers (Digital Subscriber Access Multiplexer, Digital Multiplexer Access to the Subscriber Line), placed in the local exchanges and that selectively send the requested data flow only to the DSL users (Digital Subscriber Line).

A broadcasting network, however, is not designed to provide mechanisms that selectively offer the content in response to user demands.

So far, remultiplexers have been installed, especially in the headers of digital terrestrial, cable and satellite digital television operators, so that a set of elementary streams are multiplexed to be efficiently transported on a reduced number of carriers.

The above remultiplexers can work either at a fixed coding rate or at a statistical coding rate. A fixed speed video re-multiplexer works based on a time division and assigns a fixed bandwidth to each of the input streams. However, statistical multiplexers offer a more flexible method of allocation. The latter can dynamically give priority to active flows over those that are not being demanded, thus not wasting bandwidth and consequently increasing the effective capacity.

Recently, other types of remultiplexers are being used at the border nodes with the ability to insert local and / or regional content. The border nodes are elements located in the trunk networks that act as an interface between the header and the end nodes of the access networks that give users access.

To this type of remultiplexers at the ends of the backbone networks, wavelength tunable optical filters are added so that they are able to select the wavelength that the digital program requested by a number of users takes.

The remultiplexers with fixed or statistical coding speed are not really time-adaptive and therefore your routing table must be defined in a fixed way. This type of remultiplexers are designed to be used in the header of the transport network, where the information is transmitted independently of the user demand. In addition, they cannot provide multiple transport flows to the exit.

As for the remultiplexer with the tunable optical filter, it works as if it were a remultiplexer, although it is really based on a wavelength selector. This type of configuration is associated with a complex centralized management system, since the header must be synchronized with all these remultiplexers that act as concentrators.

Another series of existing solutions in the state of

The technique in reference to systems with the ability to adapt the output signals and therefore the bandwidth depending on the user demand.

The US patent document US6909726-B1 describes a system whose objective is to provide only the services required by users in a broadcast-oriented network. The patent focuses on various algorithms that can be used to manage bandwidth efficiently. Thus, for example, the device is fed back with information about the use of the services by the users and, before unused services, allocates that bandwidth to other services that are being demanded by the users.

US Patent US6944186-B2 describes an MPEG multiple output remultiplexer that selects the output packets by their identifier according to a set of rules that can be modified. The remultiplexer is set with the input encoders to be able to insert video, audio and data into the device.

International application WO 98/16067 describes a device with two inputs and one output that combines two flows (typically an input stream that will be added to a local one) in a single flow.

Finally, the international application WO 99/37048 describes a system that performs a remultiplexing with two inputs and one output where the criteria of Filtration can be introduced using a keyboard and / or a mouse. The multiplexing algorithm results in better bandwidth efficiency, discarding as many null packets as possible.

In all these devices described above there is no real-time flexibility in changing environments and therefore they do not have the ability to dynamically modify the routing table to insert programs demanded by end users in the available multiple outbound transport streams.

The device and method of the present invention solves the previous drawbacks and can be used in the access network of the distributors and allowing the transformation of a pure broadcast transmission into a broadcast-multicast transmission mix.

Therefore, the device and method of the present invention is established for a defined group of users and assigns the content of the signal transmitted in a broadband network to a signal to be transmitted in a narrowband access network. This device and method filters the entire list of broadcasting programs depending on the user's instant choices, while making all programs available to the user at all times. As an additional advantage, the management of this system, which is capable of offering user demands at the local level, is completely decentralized.

Listed below are other advantages that are achieved with the device and method of the present invention and related to its main advantage that is an improved use of bandwidth in the access network:

Solution is given to the bottleneck in existing bandwidth in the segment of the access network that is closest to the user.

- The costs related to the use of a large bandwidth are reduced, for example those involved in obtaining a spectrum license in wireless scenarios. The provision of real video in services on demand is simplified. The digital programs requested can be automatically delivered to users without complex centralized management systems.

Therefore, the device and method of the present invention must process user requests automatically and in real time. User set-top boxes must be able to have knowledge of all available programs even when they are not actually being sent. Therefore, it will be necessary to solve the conflicts in the program identifiers that may occur when mixed with

The output of various incoming transport flows. The load of outbound transport flows should be balanced to avoid an overflow of outbound transport flows. Finally, low processing instability must be achieved since the device must work in real time.

DESCRIPTION OF THE INVENTION

The purpose of the device and method of the present invention is to assign the content of a broadband transport network to a narrowband access network by implementing intelligent multiplexing of programs on demand in real time at the access network level.

The MPEG-2 encoding considers a multimedia signal in its elementary streams (audo, video, data) (Elementary Stream-ES). The ES are divided into packages of variable length to which a header with the ES identifier is added, forming a Packetized Elemental Flow

Elementary Stream-PES).

PES packages are grouped and entered as payload in the Transport Package, which carries an identifier (PID), so that all Transport Packages with the same PID carry data from the same ES. Finally, several transport packets are multiplexed forming the transport frame consisting of 188 bytes. Each of these 188-byte packets will form what is called the transport stream. Some of these 188-byte packets of the transport stream are filled with a PCR (Program Clock Reference) time stamp to synchronize the set-top box decoder and there are other packages that contain PSI (Program Specific Information) tables.

The MPEG-2 standard establishes four types of tables and allows informational elements to be expanded, adding other types of tables:

- Program Map Table (PMT Program Map Table): indicates the locator) of the start chain of each service (associates each program with the PIDs of the packages that compose it), as well as the location of the synchronism reference of the same.

Network Information Table (NIT Network Information Table): it is a private table.

Program Association Table (PAT Program Association Table): is one of the tables for which PIDs are reserved; In its packages the information related to the PID values corresponding to the Program Map Table (PMT) and the Network Information Table (NIT) travels. Its function is therefore to indicate to the receiver where he can find the other information tables.

Conditional Access Table (CAT Conditional Access Table): reports the PIDs of the packages that contain the information of the management and control messages of each Conditional Access System.

A set of elementary streams is successively combined into a single program transport stream (SPTS Single Program Transport Stream) if only one program is involved, or a multiple program transport stream (MPTS Multiple Program Transport Stream) if the elementary streams are Associated with different programs. A number of transport flows are transmitted through the operator's network, thus requiring a large amount of bandwidth.

The proposed device is a processing system with multiple inputs and multiple MPEG-x packet outputs, which remultiplexes several input transport streams into a smaller number of outbound transport streams, leaving out some elementary input streams and giving as result a width of minor band, necessary requirement at the exit of the system. The remultiplexer maintains a table that relates the list of the program available at the exit and the outbound transport flows that transport them.

When a program request arrives at the remultiplexer, it looks in its routing table. If the program is already broadcasting, you only have to inform the set top box about the transport flow that transports the requested program. If, on the contrary, the program is not being transmitted, the remultiplexer has to add the MPEG-x packets related to the selected program to one of the outbound transport streams and therefore perform the updating of all the tables.

The MPEG-x transport stream remultiplexer system to multiplex a number of transport streams at the input of said remultiplexer system into a smaller number of transport streams at the output of said real-time remultiplexer system on demand, comprises:

- At least one reception section with means to demodulate said transport flows to the input and means to route packets of said input transport flows.

At least one transmission section with means for encoding and modulating at least one baseband signal.

- At least one multiplexing section with means for multiplexing said packets of said number of inbound transport streams into a smaller number of outbound transport streams as a function of said demand.

At least one processing section with means to establish the content of said transport flows at the exit.

Said means for demodulating said transport flows of said reception section are composed of a number of reception blocks equal to said number of input transport flows. The means of coding and modulation of said transmission section comprise at least one row of transmitter blocks and in front of said row at least one buffer.

The means of said reception section for routing said packets of said transport flows to the input comprise means for sending information packets with PSI tables to said processing section and means for sending information packets of a program demanded to a transport flow determined output, means for sending information packets with a PCR time stamp to said processing section and finally means for discarding packets other than the previous ones.

The means for multiplexing of said multiplexing section are composed of a number of multiplexer blocks equal to said number of outbound transport streams and a number of buffers. Said means perform the multiplexing:

By inserting said program information packets into said determined outbound transport stream.

Introducing PSI tables in these program packages.

Adding null padding packages.

The means for establishing the content of said transport flows in said processing section comprise

- Means for assigning PID to said packets of said transport stream.

Means for adjusting a PCR time stamp.

Means to manage at least one message with the destination set top box. These means update a program table based on said message with a received set top box, identify PID of said demanded program.

Another object of the invention is a MPEG-x transport stream remultiplexer method to multiplex a number of transport streams at the input of at least a remultiplexer system in a smaller number of transport flows at the output of said real-time remultiplexer system on demand for programs comprising:

Check if said demanded program is in said transport flow to the entrance.

Check if said demanded program is in said outbound transport flow.

Decide on the transport flow that will be carried out by said defendant program.

Decrease at least one counter.

- Manage MPEG tables consisting of:

• Update PID tables by removing unclaimed PIDs and adding new demanded PIDs

• Resolve PID conflicts

• Update PSI tables.

- Provide the set top box with information to find said demanded program

DETAILED DESCRIPTION OF THE DRAWINGS

To complete the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of figures in the accompanying part is attached as an integral part of said description. where, as an illustration and not limitation, the following has been represented:

Figure 1 shows a general scheme of the remultiplexer system with the number of incoming transport flows and the number of outgoing transport flows. Figure 2.- Shows a general scheme of a remultiplexer system.

Figure 3.- Shows a flow chart of a remultiplexing method.

Figure 4.- Shows the actions of the message manager of the processing section of a remultiplexer system.

DESCRIPTION OF A PREFERRED EMBODIMENT

In a preferred embodiment, the system and method of the present invention is implemented under the DVB standard.

The DVB standard involves inserting Service Information Tables Sl (Service Information Tables) into the MPEG stream, giving frequency / modulation data (NIT - Network Information Table), service information (SDT - Service Description Table), events (EIT - Event Information Table), and time synchronization (DTT - Tinme & Date Table). Other tables make an aggregation of services under a single entity (BAT - Bouquet Association Table), put information related to current events (RST - Running Status Table), contain a time offset to calculate the local time (TOT -Time Offset Table) or cancel invalid tables (ST - Stuffing Tables)

As shown in Figure 1, the proposed device 3 multiplexes a number n of input transport flows 1 into a smaller number m of output transport flows 2.

Figure 2 shows the system of the present invention which is formed by a reception section 200 located before the multiplexing section 210. The reception section 200 is formed by a set of demodulation cards and is responsible for providing to the multiplexing section a demodulated input signal. Therefore, the reception section 200 will be responsible for extracting MPEG-x packets from a multiplexed signal flow regardless of the broadcast transmission standard used (DVB, ATSC, ISDB)

Behind the multiplexing section 210 is the transmission section 230. The transmission section 230 is formed by a set of Modulation cards and is responsible for coding and modulating the baseband signal at the output of the multiplexing section. The transmission section 230 performs the coding and modulation according to the broadcasting transmission standard used (DVB, ATSC, ISDB)

In one embodiment, the system can be implemented with baseband (ASI) signals such as input signals and / or output signals.

The system is completed with a multiplexing section 210 and a processing section 220.

The reception section 200 comprises a number of reception blocks 201 equal to the number n of incoming transport streams. Each of the reception blocks 201 is in charge of receiving the packets of the n transport streams and routing them according to a series of internal tables fed by the main processor. Said tables dedicated to routing the packets consist of a table dedicated to the routing of the packets with the audio, data and video information (PID_Filter_Table) and another tab that routes the packets containing tables (EIT,

SDT) with the same PID but are exclusive to a program (Program_Number_Table).

In this way the packages that carry the PSI / SI tables and that are not linked to a single digital program, are sent to the processing section 220. The packages that contain compressed information of a program that must be available at the exit of the system , as well as the exclusive tables of the requested programs, are routed to the assigned outbound transport flow. Packages with PIDs corresponding to unsolicited programs will be discarded. Finally, packets containing a PCR time stamp are sent to a PCR control module, which will inform the involved multiplexer of the adjustment of this value. All these tasks are performed using the PID_Filter_Table table that associates each PID packet of information with its corresponding outbound transport flow.

The multiplexing section 210 logically connects an input with its assigned output. The multiplexing section 210 comprises a number of multiplexer blocks 212 that is equal to the number m of outbound transport streams. In Ia Multiplexing section The input data to each multiplexer block 212 may be packets with compressed data or packets of PSI / SI tables.

Packages containing compressed information are multiplexed in a scheduled outbound transport stream. Data packets with compressed information are received in each of the multiplexer blocks 212 from an array of buffers 211 (n x m). The previous arrays of buffers 211 are responsible for the variable bit rate of the incoming transport streams.

A row of n buffers 211 (i, 1 -> i, n) feeds multiplexer 212 number i which accesses its data in a fixed time division. Each multiplexer 212, by means of a Scheduler module, generates a constant bit rate (Constant Bit Rate -CBR) packet flow according to the following steps.

First, multiplexers 212 insert the PSI / SI tables periodically in each generated flow according to the time intervals defined in each of the broadcasting standards. The internal TableJJst table contains a list of the PSI / SI tables to be included in each outbound transport flow.

Secondly, the information of the programs that will be transmitted at a fixed data transfer rate is inserted into the flow generated by each multiplexer block 212.

Finally, if the data transfer rate of the flow generated by multiplexer blocks 212 is not met according to each particular standard, multiplexer blocks 212 add fill packets. To add null fill packages they will use the null packet generator.

The multiplexing action in each multiplexer block 212 involves performing two main tasks. First of all, a reallocation of the PIDs must be carried out. That is, multiplexing block 212 must resolve PID conflicts between packets that come from various transport streams. In an internal PID reallocation table, called PID_Mapping_Table, the correspondence between the new PIDs and the old PIDs is stored. Secondly the PCR must be adjusted. For this, the homonymous field of the MPEG-x packets must be modified in order to achieve the desired synchronization in the user decoders.

The correction made of the PCR value is expressed by the following formula.

New_PCR = Old_PCR + (Transfer Time - Reception Time) - Avergage_Dwell_Time

That is, for each packet the new PCR is equal to the old PCR plus its differential delay, the amount of time above or below the average delay time in the buffer that affects all packets equally.

The formula is evaluated when the PCR packet leaves multiplexer block 212

(transfer time). The reception time has been previously entered in a specific internal table, the PCR_Table, at the time it was received and the average delay (Average_Dwell_Time) is finally subtracted from the absolute delay to obtain the differential delay.

The transmission section 230 consists of a row of transmitter blocks 232 that generate the outbound transport stream in a given broadcast format. Between the output of the multiplexer blocks 212 and the transmitter blocks 232 a buffer 231 is added to avoid packet losses due to sudden bursts of data.

The processing section 220 acts as the system control module.

This module is the base section of the system since it supports the interactivity, and implements the method followed to carry out the multiplexing as shown in Figure 3.

First of all this section 220 receives the requests of a user. These user requests 310 are formed by the new program that you wish to view as well as by the old program that you wish to stop watching. In the event that the set top box was off 320, the seventh stage 360 would continue. Secondly, the processing section 220 checks if the digital program demanded by the user is available at the input of the system from the broadband transport network 330.

Next, it is checked whether the desired digital program is included in any of the outbound transport streams 340. If the program is already available, the set top box of the place where the desired program can be found is informed. If, in the opposite case, the desired program is not in the outflow, the next step is continued.

Fourthly, it is decided which transport stream the requested program 341 will carry, taking into account, on the one hand, the remaining bandwidth in each outgoing transport stream and the necessary bandwidth for the necessary digital program. The remaining bandwidth in each digital stream can be obtained from the internal occupation table (Occupation_table), which stores the data of the average bit rate of each program, as well as the total bit rate and the available bit rate in each output stream.

Fifthly, the management of the tables is carried out, both internal

(filtered / redirected), such as external MPEG / DVB PSI / SI, which are stored in the memory of the 342 350 processing system. These tables, for whose control the processor has the internal Program_Map tables (descriptive information of each program: PIDs of the audio / video / data packets, PIDs of the packets with PCR information, transport flows to the input and output) and Tablejnfo (addressing PSI / SI tables), are:

Tables of the reception section 200. The PIDs to be accepted / rejected and the outbound transport flows for the PSI / SI tables change

- Tables of the section of the multiplexing 220. The reallocation table of

PIDs are updated to resolve new PID conflicts and all PSI / SI tables are sent to the corresponding multiplexer organizer to insert them into their outbound transport streams. PSI / SI tables. Memory 222 receives the PSI / SI tables of each input transport stream, storing and updating them (if necessary) to send them to the corresponding multiplexers. The output PAT tables and PMT tables are first created by combining and rearranging the original PAT and PMT tables, and these together with the NIT tables are modified each time a digital program is changed to a different output transport stream .

Next, the counter that measures the number of spectators that the old program 361 is watching is decreased, unless the set-top box is being turned on since in that case it is not necessary to reduce the number of users by not ceasing to be seen No previous channel.

In seventh and last place, the set-top box is provided with the information necessary to host the new requested program 370.

The message management module 223 is responsible for the interaction with the user set-top boxes. The messages of the set top boxes are received through the message queue 224. In Figure 4 it is described how the communication is made between the set top box 41 and the system 40.

First, a program request 42 is made. The set top box 41 asks the system 40 for a television program demanded by a viewer.

Secondly, the updating of the program table 43 is performed. The remultiplexer 40 updates its program table with the new requested program.

Subsequently, the identification of PIDs 44 is performed. Remultiplexer 40 collects all PIDs related to the program demanded. Consequently, the remultiplexer stops the rejection of packets containing those PIDs related to the desired program.

The packets then begin to be multiplexed in the transport stream chosen by the processor 45. Fifthly, the indication is made to the set top box 41 that the program is available 46, that is, the remultiplexer 40 indicates to the set-top box 41 that the new program is ready to be received and decoded.

The set-top box 41 updates its program table 47. And finally the set-top box 41 orders its decoder to initiate the decoding of the requested program 48.

In another embodiment, the same device and method could be applied to the ATSC broadcasting standard, with the reception / transmission blocks conforming to this standard. Although some ATSC tables are named differently, both the equivalent ATSC and DVB tables share a similar structure.

In another exemplary embodiment, the same device and method could be applied for the ISDB broadcasting standard, with the reception / transmission blocks conforming to this standard. Although some ISDB tables are named differently, both the equivalent ISDB and DVB tables share a similar structure.

Claims

1. Remultiplexer system (3) of MPEG-x transport streams to multiplex a number of transport streams at the entrance (1) of said remultiplexer system into a smaller number of transport streams at the exit (2) of said remultiplexer system in real time on demand, characterized in that it comprises:

At least one reception section (220) with means for demodulating said transport flows to the input (1) and means for routing packets of said input transport flows.

At least one transmission section (230) with means for encoding and modulating at least one baseband signal.

At least one multiplexing section (210) with means for multiplexing said packets of said number of inbound transport streams (1) into a smaller number of outbound transport streams (2) as a function of said demand.

- At least one processing section (220) with means to establish the content of said transport flows at the exit (2).

2. Remultiplexer system (3) according to claim 1 characterized in that said means for demodulating said transport flows of said reception section (220) are composed of a number of reception blocks (201) equal to said number of input transport flows (one).

3. Remultiplexer system (3) according to claim 1 characterized in that said means of said reception section (220) for routing said packets of said transport flows to the input (1) comprise:

Means for sending information packets with PSI tables to said processing section (220).

Means for sending information packets of a requested program to a given outbound transport stream (2). Means for sending information packets with a PCR time stamp to said processing section (220).

Means for discarding packages other than the previous ones.

4. Remultiplexer system (3) according to claim 1 characterized in that said means for multiplexing said multiplexing section (210) is composed of a number of multiplexer blocks (212) equal to said number of outgoing transport streams (2) and a number of buffers (211).

5. Remultiplexer system according to claim 1 characterized in that said multiplexing means of said multiplexing section (210) perform the multiplexing:

Multiplexing said program information packets in said determined output transport stream (2).

Inserting PSI tables in these program packages.

Adding null padding packages

6. Remultiplexer system (3) according to claim 1 characterized in that said coding and modulation means of said transmission section (230) comprise at least one row of transmitter blocks (232) and in front of said row at least one buffer (231).

7. Remultiplexer system (3) according to claim 1 characterized in that said means for establishing the content of said transport flows in said processing section (220) comprise

Means for assigning PID to said packets of said transport stream.

Means for adjusting a PCR time stamp

Means to manage at least one message with the destination set top box.

8. Remultiplexer system (3) according to claim 7, characterized in that said means for managing at least one request message of a program with a destination set top box updates a program table based on said message with a received set top box, identifies PID of said defendant program.

9. MPEG-x transport stream remultiplexer method to multiplex a number of transport streams at the input (1) of at least one remultiplexer system (3) into a smaller number of transport streams at the output of said remultiplexer system ( 3) in real time on demand for programs characterized in that it includes:

a.- Check (320) if said demanded program is in said transport flow to the entrance (1).

b.- Check (330) if said demanded program is in said outbound transport flow (2).

c- Decide (340) said transport flow that will take said defendant program.

d.- Decrease at least one counter (361).

e.- Manage MPEG tables (342-350).

f.- Provide (370) to the set top box information to find said demanded program

10. Method according to claim 8 characterized in that said management of the MPEG tables comprises:

a.- Update PID tables eliminating PID not demanded by demanded PID,

b.- Resolve PID conflicts.

c- Update PSI tables.