JP2005184431A - Multiplexer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional multiplexer that cannot have outputted correctly corrected time reference information because the conventional multiplexer has only one buffer for rewriting the time reference information resulting in causing overwriting in the case of receiving a plurality of kinds of packets whose identification information differs from each other in the case of correcting the time reference information for countermeasuring fluctuations. <P>SOLUTION: A reception time reference information buffer 305 stores time reference information of a received time reference information packet as reception time reference information, an input phase time reference information buffer 309 stores a count for the time reference information when the reception time reference information is stored as input time reference information, an output phase time reference information buffer 310 stores a count for time reference information when a rewritten time reference information packet is outputted as output time reference information, and a time reference information packet generating section 306 subtracts the input time reference information from the output time reference information, adds the difference to the reception time reference information and uniquely outputs a time reference information packet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multiplexing apparatus for multiplexing and transmitting a plurality of encoded packet data in packet units for packet data composed of digital signals, particularly packet data generated by encoding video, audio, etc. In particular, the present invention relates to a multiplexing apparatus that can suppress fluctuations in time reference information in packet data due to delay fluctuations during multiplexing.

The conventional multiplexing apparatus sets the value of the time reference information in the received packet data as an initial value in a counter in the multiplexing apparatus, and outputs the time reference information when the packet data including the time reference information is multiplexed and output. The fluctuation at the time of packet data multiplexing is corrected by replacing the value with the counter value and performing multiple output. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 11-41193 (FIG. 1)

  Next, in order to clarify the usage pattern of the present invention, differences between the patent document 1 and the usage pattern of the present invention will be described with reference to the drawings. FIG. 3 is a schematic diagram of FIG. In the video / audio encoding device 500, the video encoding unit 501 and the audio encoding unit 502 encode the video signal and the audio signal, respectively, based on the clock generated by the clock generation unit 504.

  Further, the time reference information encoding unit 503 encodes the clock of the clock generation unit 504 as counter information. The video / audio encoding device 500 multiplexes and outputs the video / audio encoded data and the time reference information encoded data. On the other hand, the video / audio decoding device 520 decodes the received time reference information by the time reference information decoding unit 523, and based on this value, the clock used by the encoding device side is sent to the clock reproduction unit 524. The video decoding unit 521 and the audio decoding unit 522 decode the video signal and the audio signal, respectively, based on the reproduced clock.

  If fluctuations occur in the timing at which the time reference information arrives at the video / audio decoding device 520 due to fluctuations in the transmission path 510 or the like, there will be a problem that the reproduced clock will fluctuate and video and audio cannot be correctly decoded. For this reason, transmitting the time reference information to the decoding device without fluctuation is an extremely important element for stably providing a service for distributing encoded data such as video and audio. It has been solved.

  FIG. 4 is an explanatory diagram of a multiplexing apparatus that is an object of the present invention. When the transmission bandwidth of the transmission path is wide, not only packet data encoded by one video / audio encoding device is transmitted, but encoding is performed by a plurality of video / audio encoding devices as shown in FIG. An operation mode is used in which the video / audio packet data is multiplexed by a multiplexing device, or a multiplexing device is installed at a subsequent stage to efficiently use the transmission band. Since the multiplexer simultaneously multiplexes packet data from a plurality of video / audio encoders and time-division multiplexes them, the value of the time reference information fluctuates by the processing delay in the multiplexer. A process for correcting the error is required.

  The multiplexing apparatus shown in FIG. 1 of Patent Document 1 operates effectively as the first-stage multiplexing apparatuses 620 and 621 shown in FIG. However, when a packet containing multiple types of time reference information multiplexed on the same line is received as in the multiplexing device 630 installed in the second stage, all the time reference information can be corrected correctly. It has a problem that it cannot be done.

  The present invention has been made in order to solve the above-described problems, and received a packet including a plurality of different types of time reference information as well as one type of time reference information included in the received packet. Even in such a case, an object is to provide a multiplexing apparatus capable of correcting fluctuations in time reference information during packet multiplexing.

  A multiplexing device according to the present invention includes a reception time reference information buffer that holds time reference information of an input time reference information packet as reception time reference information, a time reference information counter uniquely provided in the multiplexing device, An input time reference information buffer that holds the time reference information counter value when the reception time reference information is held in the reception time reference information buffer as input time reference information, and a time when the rewritten time reference information packet is output The output time reference information buffer that holds the counter value for reference information as output time reference information, and the input time reference information is subtracted from the output time reference information, and the difference value is added to the reception time reference information and rewritten independently. And a time reference information packet generator for outputting the time reference information packet.

  According to the present invention, in the multiplexing apparatus, the time reference information packet generator generates a time reference information that is uniquely rewritten by subtracting the input time reference information from the output time reference information and adding the difference value to the reception time reference information. Since the packet is output, it is possible to correct the fluctuation of the time reference information when the data packet is multiplexed even when a packet including a plurality of different types of time reference information is received on the same line.

Embodiment 1 FIG.
1 is a block diagram of a multiplexing apparatus shown in Embodiment 1 of the present invention. In the figure, reference numeral 300 denotes a multiplexing device according to the present invention, an input processing unit 321 for packet input 1, an input processing unit 322 for packet input 2, an input processing unit 32n for packet input n, and an input processing unit 321 to an input processing unit. It is composed of a channel multiplex processing unit 331 that multiplex-outputs packets output from 32n.

  Hereinafter, the input processing unit 321 will be described in more detail. Reference numeral 301 denotes a packet extraction unit that extracts only multiplexed packets from received packets, 302 denotes a packet identification information change unit that changes packet identification information of the packet extracted by the packet extraction unit 301, and 303 denotes a packet identification information change unit 302. A time reference information detection unit that detects a packet including time reference information (hereinafter referred to as a time reference information packet) from the output packets, and 304 is a buffer unit that temporarily holds packets other than the time reference information packet. , 305 is a reception time reference information buffer unit that temporarily holds the time reference information detected by the time reference information detection unit 303.

  Further, reference numeral 306 denotes a time reference information packet generation unit that independently generates a time reference information packet, reference numeral 307 denotes a time reference information counter for generating the time reference information packet, and reference numeral 308 denotes a clock signal for operating the time reference information counter 307. 309 is a clock generation unit that supplies the input phase time reference information that holds the count value of the time reference information counter 307 at the timing when the time reference information detection unit 303 detects a packet including the time reference information from the received packet. It is a buffer part.

  Reference numeral 310 denotes output phase time reference information that holds the count value of the time reference information counter 307 at the timing when the multiplexing control unit 312 described later selects multiplexing of the time reference information packet generated by the time reference information packet generation unit 306. The buffer unit 311 is a packet multiplex processing unit that multiplexes the packet from the buffer unit 304 and the time reference information packet from the time reference information information packet generation unit 306, and 312 is a packet from the buffer unit 304 to the packet multiplex processing unit 311. And a multiplexing control unit that controls which of the time reference information packets from the time reference information packet generation unit 306 is multiplexed.

  Next, the operation will be described. The multiplexing apparatus 300 of FIG. 1 is roughly composed of n input processing units (input processing unit 321 to input processing unit 32n) and a multiplex output unit 331. Since the input processing unit 321 to the input processing unit 32n all have the same configuration, the operation of the input processing unit 321 will be described in detail as a representative.

  The packet extraction unit 301 extracts only packets to be multiplexed by the multiplexing device 300 from the received packet signals. For example, among the received packets, stuff packets and packets that do not need to be multiplexed are deleted by the packet extraction unit 301, and only other necessary packets are output.

  The packet identification information changing unit 302 changes the packet identification information as necessary for the packet extracted by the packet extracting unit 301. Usually, identification information for identifying the packet type is added to the packet, but the multiplexing device 300 can multiplex and input a plurality of types of packets on the same line as shown in FIG. It has become. Since this is the same for packet input 2 to packet input n, when a packet whose identification information overlaps with a packet from another packet input is received, the identification information is changed. This avoids duplication of identification information at the time of multiplex output from the channel multiplex processing unit 331.

  The time reference information detection unit 303 searches for the time reference information packet from the packets input from the packet identification information change unit 302, stores the time reference information value in the reception time reference information buffer 305, and for the time reference information The count value of the counter 307 is stored in the input phase time reference information buffer unit 309. Packets other than the time reference information packet are stored in the buffer 304.

  In addition, the time reference information packet generation unit 306 generates a time reference information packet uniquely in the multiplexing apparatus 300. The packet multiplex processing unit 311 performs multiplex output processing of the packet from the buffer unit 304 and the time reference information packet from the time reference information packet generation unit 306. The multiplexing control unit 312 controls which of the packet from the buffer unit 304 and the time reference information packet from the time reference information packet generation unit 306 is multiplexed, and the time reference information packet from the time reference information packet generation unit 306. The count value of the time reference information counter 307 is stored in the output phase time reference information buffer 310 at the timing when is selected.

  The time reference information value generated by the time reference information packet generation unit 306 is generated by reading values from the reception time reference information buffer unit 305, the input phase time reference information buffer 309, and the output phase time reference information buffer unit 310. Specifically, the reception time reference information buffer 305 holds a difference value between the time reference information value stored in the input phase time reference information buffer 309 and the time reference information value stored in the output phase time reference information buffer 310. To be added to the time reference information value. The channel multiplex processing unit 331 multiplexes and outputs the packets from the input processing unit 321 to the input processing unit 32n.

  Next, the time reference information packet generation operation by the time reference information packet generation unit 306 will be described in detail. FIG. 5 is a configuration diagram of a multiplexing apparatus that inputs and multiplexes a plurality of types of packets. In FIG. 5, reference numerals 701 and 702 denote video / audio encoding apparatuses that generate packet data by encoding video and audio signals. Reference numeral 703 denotes a multiplexing device that multiplex-outputs packet data from the video / audio encoding device 701 and the video / audio encoding device 702 in a time division manner, and corresponds to the multiplexing device shown in FIG. Reference numeral 704 denotes a multiplexing device used for explaining the present invention.

  It is assumed that the video / audio encoding device 701 and the video / audio encoding device 702 operate with independent time reference information packets PCRa and PCRb, respectively. FIG. 6 is an explanatory diagram showing an operation example of a conventional multiplexing apparatus. That is, when the configuration of the multiplexing device 704 in FIG. 5 is equivalent to that of the multiplexing device 703, the time reference information packet output from the video / audio encoding device 701 and the video / audio encoding device 702 shown in FIG. An example of operation when multiplexed by the multiplexing device 703 and the multiplexing device 704 is shown.

  The video / audio encoding device 701 includes a video packet Vae (e = 1, 2, 3...), An audio packet Aaf (f = 1, 2, 3,...), A time reference information packet PCRag (g = 1, 2, 3 ...) packets are output. The video / audio encoding device 702 includes Vbh (h = 1, 2, 3...), Audio packet Abj (j = 1, 2, 3...), Time reference information packet PCRbk (k = 1, 2,. 3 ...) packet is output. The multiplexing device 703 multiplex-outputs the packets output from the video / audio encoding device 701 and the video / audio encoding device 702 in a time division manner. In FIG. 6, T1 indicates a processing delay in the multiplexing apparatus 703, and T2 indicates a processing delay in the multiplexing apparatus 704.

  A multiplexing device 704 equivalent to the multiplexing device 703 (hereinafter referred to as conventional) extracts time reference information from the time reference information packet, and this is extracted from the counter 2 shown in FIG. This is the initial value. That is, when the time reference information packet PCRa1 shown in FIG. 6 is received, the time reference information is set as an initial value in the conventional counter. Next, when the time reference information packet PCRb1 is received, the time reference information is overwritten and set in the conventional counter as an initial value.

  On the other hand, when the time reference information packet PCRa1 is independently output from the conventional multiplexer 704, the count value of the conventional counter is read at the timing when the time reference information packet PCRa1 is read from the buffer, and the value is read as the time reference information packet PCRa1. Replace with the time reference information value and output. However, at this time, the conventional counter has already performed a counting operation based on the time reference information value input from the time reference information packet PCRb1, and correct correction cannot be performed.

  In order to explain more specifically with respect to the above, the time information that we routinely use is applied as the time reference information. From the video / audio encoding devices 701 and 702, the time reference information, that is, every 10 seconds, Time information is inserted into a time reference information packet and output. Since the time reference information of the video / audio encoding device 701 and the video / audio encoding device 702 is independent, for example, the time reference information packet PCRa1 output from the video / audio encoding device 701 is 11:29:30 And the time reference information packet PCRa2 indicates 11:29:40. On the other hand, it is assumed that the time reference information packet PCRb1 output from the video / audio encoding device 702 indicates 07:05:15, and the time reference information packet PCRb2 indicates 07:05:25.

  When receiving the time reference information packet PCRa1, the conventional multiplexing device 704 sets the value of the conventional counter to 11:29:30, and immediately after receiving the time reference information packet PCRb1, sets the value of the conventional counter to 07:05. Set a new 15 seconds. For this reason, at the timing of outputting the time reference information packet PCRa1, a value of (07: 05: 15 + T4) is inserted into the time reference information packet PCRa1 instead of (11: 29: 30 + T3) which should originally be. Therefore, the time reference information is not corrected correctly.

  Next, FIG. 7 shows an operation example when the multiplexing apparatus 704 in FIG. 5 is the multiplexing apparatus 300 shown in FIG. 1 according to the present invention. FIG. 7 is an explanatory diagram showing an operation example of the multiplexing apparatus of the present invention.

  Multiplexer 300 includes a time reference information counter 307 at a timing at which time reference information detection section 303 detects time reference information in a received packet and at a timing at which time reference information packet generation section 306 multiplex-outputs the time reference information packet. The count value is held in the input phase time reference buffer 309 and the output phase time reference buffer 310. Further, the time reference information packet generation unit 306 independently generates a time reference information packet by holding the time reference information included in the received packet in the reception time reference information buffer 305.

  In the example of FIG. 7, the time reference information packet PCRan (n = 1, 2, 3...) From the video / audio encoding device 701 is set to 5 as the retransmission interval of the time reference information packet output from the multiplexing device 704. At the packet interval, the time reference information packet PCRbm (m = 1, 2, 3,...) From the video / audio encoding device 702 is output at an interval of 7 packets, which is different from the received interval. An example of operation in the case of performing is shown.

  For example, at the timing when the time reference information packet PCRa0 is received, the time reference information (11:29:20) included in the time reference information packet PCRa0 is held in the reception time reference information buffer 309, and the time reference information packet PCRa0 is stored. The count value (21:29:52) of the time reference information counter 307 at the received timing is held in the input phase time reference information buffer 309.

  Next, at the timing at which the time reference information packet generation unit 306 independently generates and outputs the time reference information packet PCRa0, the count value (21:30:06) of the time reference information counter 307 at this timing is output. Stored in the time reference information buffer 310. Thereby, the difference value (14 seconds) is added to the time reference information (11:29:20) received first and held in the reception time reference information buffer 305, and the time reference information value of the time reference information packet is added. Set to 11:29:34.

  The time reference information packet PCRbm (m = 0, 1, 2,...) Related to the video / audio encoding device 702 is corrected in the same manner. In order to realize the above-described operation using the reception time information reference buffer 305, the input phase time reference buffer 309, and the output phase time reference buffer 310, the number of each of the plurality of types of packets having different identification information is used. When the time reference information packet generating unit 306 generates a time reference information packet that is uniquely rewritten, the reception time reference information, the input time reference information, and the output time reference information for each identification information held by each of the buffers are provided. Although it is necessary to extract and calculate, since this method can be easily implemented, detailed description is omitted.

  As described above, in the multiplexing apparatus 300 according to the present invention, when correcting the time reference information, the time reference information counter 307 provided in the apparatus sets the value of the received time reference information as an initial value. Instead, it is used as means for measuring the difference time between the timing of receiving a packet including time reference information and the timing of outputting a packet including time reference information. In addition, since the time reference information packet generation unit 306 subtracts the input time reference information from the output time reference information, adds the difference value to the reception time reference information, and outputs a uniquely rewritten time reference information packet. Even when a packet containing a plurality of different types of time reference information on the line is received, it is possible to correct fluctuations in the time reference information when data packets are multiplexed.

  Further, by separating the time reference information in the received packet from other packets and holding it, it is possible to multiplex output of the time reference information at a timing independent of the multiplexing timing of the time reference information in the received packet. Furthermore, when updating the time reference information held in the reception time reference information buffer 305, it is updated once every time a predetermined number of time reference information packets for each piece of identification information are input. The fluctuation can be corrected, and the fluctuation correction accuracy is further improved.

  In FIG. 1, each of the input processing unit 321 to the input processing unit 32n is provided with a time reference information counter and a clock generation unit. However, as shown in FIG. 2, the time reference information counter is common to all input processing units. 407 and a clock generation unit 408 may be provided.

  As an application example of the present invention, when multi-channel broadcasting is performed by multiplexing a plurality of programs in a digital broadcasting service or a video distribution system, a plurality of outputs from an encoding device that encodes video / audio related to each program are multiplexed. It can be used for multiplexing equipment.

It is a block diagram of the multiplexing apparatus shown in Embodiment 1 of this invention. It is a block diagram of the multiplexing apparatus shown in Embodiment 2 of this invention. FIG. 4 is a schematic diagram of FIG. 3 of Patent Document 1. It is explanatory drawing of the multiplexing apparatus used as the object of this invention. It is a block diagram of the multiplexing apparatus which inputs and multiplexes multiple types of packets. It is explanatory drawing which shows the operation example of the conventional multiplexing apparatus. It is explanatory drawing which shows the operation example of the multiplexing apparatus of this invention.

Explanation of symbols

300, 400 Multiplexer 301, 401 Packet extraction unit 302, 402 Packet identification information change unit 303, 403 Time reference information detection unit 304, 404 Buffer 305, 405 Reception time reference information buffer 306, 406 Time reference information packet generation unit 307 407, time reference information counter 308, 408 clock generation unit 309, 409 input phase time reference information buffer 310, 410 output phase time reference information buffer 311, 411 packet multiplexing processing unit 312, 412 multiplexing control units 321-32n, 421 42n input processing unit 331, 431 channel multiplex processing unit

Claims (3)

In a multiplexing device that inputs a plurality of types of packets with different identification information multiplexed externally on the same line, and rewrites and outputs the input time reference information packet uniquely,
A reception time reference information buffer for holding the time reference information of the input time reference information packet as reception time reference information;
A time reference information counter uniquely provided in the multiplexer;
An input time reference information buffer that holds, as input time reference information, a counter value for time reference information when the reception time reference information is held in the reception time reference information buffer;
An output time reference information buffer for holding the time reference information counter value when outputting the rewritten time reference information packet as output time reference information;
A time reference information packet generating unit for subtracting input time reference information from the output time reference information, adding the difference value to the reception time reference information, and outputting the uniquely rewritten time reference information packet. A multiplexing device characterized. The reception time reference information buffer, input time reference information buffer, and output time reference information buffer are provided for each of a plurality of types of packets having different identification information, and the time reference information packet generation unit independently generates a time reference information packet. 2. The multiplexing apparatus according to claim 1, wherein when performing, the reception time reference information, the input time reference information, and the output time reference information for each identification information held by each of the buffers are extracted and calculated. . 3. The reception time reference information stored in the reception time reference information buffer is updated once every time a predetermined number of time reference information packets for each identification information are inputted. The multiplexing device according to any one of the items.

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