JP2010041494A - Network terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network terminal capable of easily obtaining a maximum band required for transmitting a stream. <P>SOLUTION: A TTS (Timestamped Transport Stream) discrimination unit 11 discriminates whether or not a packet received from a broadband network is a packet corresponding to a stream requested via a private network and the TTS. A bit rate calculation unit 12 calculates a bit rate of the stream by referring to a time stamp added to the packet discriminated as a TTS by the TTS discrimination unit 11. On the basis of the bit rate calculated by the bit rate calculation unit 12, a gate control unit 17 controls transmission of packets stored in buffers 0 to N (18-0 to 18-N), thereby controlling a band to be allocated to the stream. Therefore, the band required for transmitting the stream can be easily controlled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for transmitting an IP (Internet Protocol) packet constituted by a plurality of transport streams (TS), and in particular, transmits a TTS (Timestamped TS) stream to which a time stamp is added while securing a band. Related to the network terminal.

  In recent years, systems for transmitting and receiving video signals via the Internet network have become widespread. In a server and set top box (STB) used in such a system, a communication protocol using MPEG (Moving Picture Experts Group) 2-TS (Transport Stream) is often used for transmission and reception of video signals.

  MPEG2-TS is composed of a plurality of transport packets (hereinafter also referred to as TS packets). Each TS packet has a size of 188 bytes or 204 bytes. The TS includes a valid TS including AV information and a TS including no information (hereinafter referred to as a null TS) inserted for matching the rate.

  In the conventional TS server device, an IP packet is configured including a null TS, and the IP packet is transmitted to the decoder side. In order to solve this problem, a technique for configuring an IP packet using a TS to which a time stamp is added (hereinafter also referred to as TTS) has been conventionally used.

  FIG. 6 is a diagram for explaining TTS. As shown in FIG. 6A, the null TS is deleted from the original TS stream to form an IP packet. At this time, an IP packet is constructed by adding a time stamp (T1 to T5) to each TS packet (TS1 to TS5) so that the decoder can correctly decode.

  As shown in FIG. 6B, the TTS has a configuration in which a 4-byte time stamp is added to a 188-byte (or 204-byte) TS packet.

  There are inventions disclosed in the following Patent Documents 1 to 4 as techniques for configuring an IP packet with such TS packets and TTS packets and transmitting them to the decoder side.

  The content distribution server disclosed in Patent Document 1 stores a portion of the streaming data to which time information is added excluding the time information, using a device unique key, and stores the encrypted data in a storage unit. In response to the request for the encrypted streaming data at the position, the partial encrypted streaming data stored in the storage means is searched based on the time information.

  When receiving the content list request signal and the reproduction condition information from the client device, the server device disclosed in Patent Document 2 compares the reproduction condition information with its own content list, and there is content that cannot be decoded by the client device. In this case, it is determined whether the content can be converted in its own format. If it is not possible, it is determined whether the content can be converted in the server device by referring to the convertible information of the server device. Then, the server device transmits a content list in which only the content that can be decoded by the client device is described to the client device, and when there is a content request from the client device, the server device converts the format itself according to the content, or The second server device is requested to convert the format, and the converted content is played back on the client device.

  In the receiving apparatus disclosed in Patent Document 3, the front end unit receives a transport stream transmitted from a broadcasting station by a broadcast wave, and outputs the transport stream to a demultiplexer. The network I / F receives, for example, a packet stream composed of at least a time stamp and one or more TS packets, which are continuous in a predetermined unit, by performing communication using HTTP. The TS synchronization extraction unit outputs TS packets in a predetermined unit to the demultiplexer based on the count value supplied from the TS synchronization clock counter. The reproduction unit reproduces TS packets supplied from the front end unit and the TS synchronization extraction unit.

In the stream processing device disclosed in Patent Document 4, the PAT / PMT buffer stores the PAT / PMT and outputs it to a recording stream. The time stamp adding unit adds a time stamp indicating the input time to the transport packet of the input partial stream, and outputs it to the TS packet buffer. The TS packet buffer stores a transport packet to which a time stamp has been added with a predetermined capacity and outputs the transport packet to the recording stream generation unit. Then, the recording stream generation unit generates a recording stream in which the PAT / PMT is arranged at the head of the transport packet to which the time stamp is added.
JP 2008-9303 A JP 2008-5254 A JP 2005-151434 A JP 2003-78875 A

  When decoding the TS stream distributed from the TS server device on the decoder side, it is necessary that the TS packet to be decoded arrives at the time of decoding in order to perform decoding correctly. Therefore, when the STB or the like relays the TS stream, it is necessary to transmit the TS stream to the decoder side while securing the band.

  However, since the null TS is deleted from the TS stream to which the time stamp is added as described above, the maximum bit rate of the original TS stream cannot be grasped, and band allocation can be performed correctly by the STB or the like. There is a problem that can not be. This problem cannot be solved even if the inventions described in Patent Documents 1 to 4 described above are used.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a network terminal capable of easily obtaining the maximum bandwidth required for stream transmission.

  Another object of the present invention is to provide a network terminal capable of efficiently performing bandwidth allocation.

  According to an aspect of the present invention, a network terminal that transmits a transport stream with a time stamp added thereto, wherein a packet received from a wide area network is a packet corresponding to a stream requested via a local area network. Determining means for determining whether or not there is a bit rate calculating means for calculating a bit rate of the stream with reference to a time stamp added to a packet determined to correspond to the stream requested by the determining means; And control means for controlling the bandwidth allocated to the stream based on the bit rate calculated by the bit rate calculation means.

  Since the control means controls the bandwidth allocated to the stream based on the bit rate calculated by the bit rate calculation means, it becomes possible to easily control the bandwidth required for stream transmission.

  Preferably, the bit rate calculation means sets a minimum value of a time stamp interval added to the packet as a bit rate.

  Therefore, the bit rate of the original transport stream can be easily calculated.

  Preferably, the network terminal further includes a buffer capacity calculating unit that calculates and allocates a buffer capacity necessary for the stream based on the bit rate calculated by the bit rate calculating unit.

Therefore, the buffer can be used efficiently.
Preferably, the network terminal further includes management means for analyzing the contents of the packet received via the local network and managing the stream by extracting the stream transmission start request and the reception address.

  Therefore, it is possible to easily manage the stream requested through the local network.

  According to an aspect of the present invention, since the control unit controls the band allocated to the stream based on the bit rate calculated by the bit rate calculation unit, the band necessary for transmission of the stream can be easily controlled. Is possible.

  FIG. 1 is a block diagram showing a configuration example of a network terminal according to the embodiment of the present invention. This network terminal determines whether or not the TTS packet requires bandwidth control according to the type of packet received from a wide area network such as the Internet, and performs bandwidth control on the TTS packet to transmit the packet. Unit 1, a bandwidth management unit 2 that receives a stream request from a PC (Personal Computer), STB, etc., and manages the stream request source, and an input port 3.

  The input port 3 is connected to a terminal device such as a PC or STB via a local network such as a LAN (Local Area Network), receives a packet from the terminal device, and outputs the packet to the bandwidth management unit 2.

  The bandwidth management unit 2 analyzes the contents of the packet received from the input port 3 and extracts information such as a stream distribution start / stop request and a reception address (distribution destination address). Then, the extracted information is output to the bandwidth control unit 1 to specify stream distribution. Details of the bandwidth management unit 2 will be described later.

  The bandwidth control unit 1 includes a TTS determination unit 11, a bit rate calculation unit 12, a reception buffer creation unit 13, a management table 14, an IP packet distribution unit 15, and output ports 1 to M (16-1 to 16). -M).

  The output port 1 (16-1) includes a gate control unit 17 and buffers 0 to N (18-0 to 18-N). The output ports 2 to M (16-2 to 16-M) have the same configuration as the output port 1 (16-1).

  When receiving a packet from the wide area network, the TTS discrimination unit 11 outputs the packet to the bit rate calculation unit 12 if the packet is a stream designated by the bandwidth management unit 2 and is a TTS. If the stream is other than TTS, the packet is stored in buffer 0 (18-0) of output port 1 (16-1).

  Here, the TTS discriminating unit 11 has a size obtained by subtracting the size of the RTP header from the payload size of the UDP (User Datagram Protocol) header of the received stream, which is a multiple of 192 bytes, and the first 5 bytes of the RTP payload. If there is a Sync byte in the TS header, it is determined that the stream is a TS with a time stamp.

The bit rate calculation unit 12 calculates the bit rate of the original TS stream by extracting the time stamp added to the TTS packet received from the TTS discrimination unit 11. Assuming that the extracted time stamps are T ₁ , T ₂ ,..., T _n , first, the minimum value Tmin of the time stamp interval is calculated by the following equation.

Tmin = min (T ₂ −T ₁ , T ₃ −T ₂ ,..., T _n −T _n−1 ) (1)
Next, the bit rate calculation unit 12 calculates the bit rate Bit (n) of the original TS stream from the minimum value Tmin of the time stamp interval by the following equation.

Bit (n) = (188 bytes × 8 bits) ÷ (Tmin / 27 MHz) (2)
Also, the bit rate calculation unit 12 calculates the maximum bandwidth required for transmission of the TTS stream by the following equation. It is assumed that seven TTS packets are included in one IP packet.

Maximum bandwidth = Bit (n) × (IP packet size) / (188 bytes × 8 bits × 7 packets) (3)
The reception buffer creation unit 13 calculates a required buffer capacity (buffer depth) Ln from the bit rate Bit (n) calculated by the bit rate calculation unit 12 by the following equation. α is a predetermined constant. For example, if data transmitted in one second is stored in a buffer, α is set to a value close to “1”.

Ln = Bit (n) × α (4)
The reception buffer creation unit 13 divides the buffer in the output port 1 based on the calculated buffer capacity Ln of each stream, and assigns each stream to buffers 0 to N (18-0 to 18-N). The buffer is composed of one memory chip, and the area of the memory chip is divided according to the buffer capacity Ln and allocated for storing each stream. Further, the buffer may be constituted by a plurality of memory chips, and the total capacity of the plurality of memory chips may be divided according to the buffer capacity Ln and allocated for storing each stream.

  Further, the reception buffer creation unit 13 calculates the gate opening time from the maximum bandwidth necessary for each TTS stream.

  FIG. 2 is a diagram for explaining the gate opening time. For example, as shown in FIG. 1, a case is considered where the bit rates of the streams accumulated in the buffers 0 to 3 (18-0 to 18-3) are 75 Mbps, 10 Mbps, 10 Mbps, and 5 Mbps, respectively. As shown in FIG. 2, the gate is opened for 15 ms for transmission of packets stored in buffer 0 (18-0) in 20 ms. Assuming that the unit time (time slot) B for opening the gate is 1 ms, the gate is opened twice for transmission of the packet stored in the buffer 1 (18-1) during 20 ms, and the buffer 2 (18-2). The gate is opened twice for transmission of the packet stored in (1), and the gate is opened once for transmission of the packet stored in the buffer 3 (18-3).

  As a result, a bandwidth of 10 Mbps is secured for the TTS stream stored in the buffer 1 (18-1), and a bandwidth of 10 Mbps is secured for the TTS stream stored in the buffer 2 (18-2). 3 (18-3), a bandwidth of 5 Mbps is secured for the TTS stream accumulated. Note that the transmission rate of packets output from the output port 1 (16-1) is 100 Mbps or more.

  For each requested stream, the reception buffer creation unit 13 sends the transmission destination address of the stream received from the bandwidth management unit 2, the calculated bit rate Bit (n), the buffer number (0 to N), the buffer capacity (buffer depth). Then, information such as the gate opening time is registered in the management table 14.

  The IP packet distribution unit 15 refers to the management table 14 and determines whether or not a packet received from the wide area network corresponds to a registered stream. If it is a registered stream, it is determined in which buffer it is stored by referring to the IP address. If the stream is not registered, it is stored in buffer 0 (18-0).

  The gate control unit 17 refers to the gate opening time of each stream registered in the management table 14 and secures the bandwidth of each stream by opening the gate as described with reference to FIG.

  FIG. 3 is a block diagram illustrating a configuration example of the bandwidth management unit 2. The bandwidth management unit 2 includes a request source packet extraction unit 21 and a snooping unit 22.

  When receiving a packet from the input port 3, the request source packet extraction unit 21 extracts a packet from a device such as a PC or STB that is a stream request source by an IP filtering function or the like.

  The snooping unit 22 analyzes the content of the packet from the request source of the stream extracted by the request source packet extraction unit 21. For example, by analyzing stream requests using IGMP (Internet Group Management Protocol), RTSP (Real Time Streaming Protocol), etc., it is possible to determine stream delivery start requests, stream delivery stop requests, etc. The original address is extracted and output to the bandwidth controller 1.

  FIG. 4 is a flowchart for explaining the processing procedure of the bandwidth management unit 2. First, when a packet is received from a device such as a PC or STB whose input port 3 is connected to the local network, the request source packet extraction unit 21 extracts a packet from the device requesting the stream from the received packet, The data is output to the snooping unit 22 (S11).

  Next, the snooping unit 22 analyzes the packet from the request source extracted by the request source packet extraction unit 21, determines the stream reception start request / stop request, and extracts the request source address (reception address) (S12).

  Finally, the snooping unit 22 outputs the stream reception start request / stop request and the reception address to the bandwidth control unit 1 (S13), and ends the process.

  FIG. 5 is a flowchart for explaining a procedure for creating the management table 14 in the bandwidth control unit 1. First, the TTS discriminating unit 11 discriminates whether or not the packet received from the wide area network corresponds to the stream designated by the band management unit 2 and is a TTS packet (S21). If the received packet is not a TTS packet (S21, No), the process ends. At this time, the received packet is stored in buffer 0 (18-0).

  If the received packet is a TTS packet (S21, Yes), the bit rate calculation unit 12 calculates the bit rate Bit (n) of the original TS stream by the above calculation method (S22). Then, the maximum bandwidth is calculated from the calculated bit rate Bit (n) by the above-described method (S23).

  Next, the reception buffer creation unit 13 calculates a necessary buffer capacity (buffer depth) from the bit rate Bit (n) calculated by the bit rate calculation unit 12 by the above calculation method, and allocates a buffer for each stream. (S24).

  Next, the reception buffer creation unit 13 obtains the gate opening time by the above method. For each stream, the transmission destination address of the stream received from the bandwidth management unit 2, the calculated bit rate Bit (n), the assigned buffer number (0 to N), the buffer capacity (buffer depth), the gate open time, etc. Is registered in the management table 14 (S25), and the process ends.

  When there is a stream transmission stop request from the bandwidth management unit 2, the reception buffer creation unit 13 releases the buffer corresponding to the stream and releases the bandwidth allocated to the stream.

  As described above, according to the network terminal in the present embodiment, the bit rate calculation unit 12 calculates the bit rate of the original TS stream from the time stamp interval added to the TTS packet. It has become possible to easily determine the maximum bandwidth required for stream transmission.

  In addition, since the reception buffer creation unit 13 calculates and allocates the buffer capacity necessary for the stream from the bit rate calculated by the bit rate calculation unit 12, it becomes possible to use the buffer efficiently. It was.

  Further, when there is a stream transmission stop request from the bandwidth management unit 2, the reception buffer creation unit 13 releases the bandwidth allocated to the stream, so that the bandwidth allocation can be performed efficiently. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a block diagram which shows the structural example of the network terminal in embodiment of this invention. It is a figure for demonstrating gate open time. 3 is a block diagram illustrating a configuration example of a bandwidth management unit 2. FIG. 5 is a flowchart for explaining a processing procedure of a bandwidth management unit 2; 4 is a flowchart for explaining a procedure for creating a management table 14 in the bandwidth control unit 1. It is a figure for demonstrating TTS.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Band control part, 2 Band management part, 3 Input port, 11 TTS discrimination | determination part, 12 Bit rate calculation part, 13 Reception buffer preparation part, 14 Management table, 15 IP packet distribution part, 16-1-16-M Output Port, 17 gate control unit, 18-0 to 18-N buffer, 21 request source packet extraction unit, 22 snooping unit.

Claims (4)

A network terminal that transmits a transport stream to which a time stamp is added,
Determining means for determining whether a packet received from the wide area network is a packet corresponding to a stream requested through the local area network;
A bit rate calculating unit that calculates a bit rate of the stream with reference to a time stamp added to a packet determined to correspond to the stream requested by the determining unit;
A network terminal comprising: control means for controlling a bandwidth allocated to the stream based on the bit rate calculated by the bit rate calculating means.   The network terminal according to claim 1, wherein the bit rate calculation means uses a minimum value of a time stamp interval added to the packet as a bit rate.   3. The network terminal according to claim 1, further comprising buffer capacity calculating means for calculating and assigning a buffer capacity required for the stream based on the bit rate calculated by the bit rate calculating means. .   The network terminal further includes management means for analyzing a content of a packet received via a local network and managing a stream by extracting a stream transmission start request and a reception address. The network terminal described in 1.

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