JP2000013441A - Packet transmitter, packet transmission method, packet multiplexer and output enable time calculating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide packet transmission equipment capable of transmitting not only the stream data of a fixed rate but also the image/sound of a variable rate. SOLUTION: An output enable time calculating means 101 obtains leading output enable time as the minimum value of time when an input packet can be outputted. A time comparing means 102 compares the leading output enable time with current time shown by a reference clock 103 and outputs 'validity' or 'invalidity'. While the 'validity' is outputted from the time comparing means 102, an output timing determining means 104 calculates the timing of packet output. Then, an output control means 107 outputs the input packet based on the instruction of the output timing determining means 106. Thus, even when the input packet stream contains the video/audio data of the variable rate, packet data can be transmitted without the overflow of a buffer at reception equipment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet transmission device, a packet transmission method, a packet multiplexing device, and an output available time calculation device in the field of digital transmission.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing a configuration example of a conventional packet transmitting apparatus. The output timer 704 is reset at a reference time serving as a reference for starting output of an input packet sequence, and outputs a time elapsed from the reference time by counting frame pulses of a fixed cycle input via the input terminal 712. Things. The output data amount counter 705 accumulates the data lengths of the packets actually output after the reference time, and provides the result to the output timing determination means 706. The output timing determining means 706 includes:
The output timing of the packet is controlled so that the output rate of the packet becomes a predetermined average rate. The output control means 707 comprises:
06 based on the output timing indicated by the input terminal
It controls the output of an input packet sequence input through the input terminal 10 and outputs the packet sequence through the output terminal 711. The output terminal 711 is connected to a receiving device (not shown) via a network or the like.

[0003] The operation of the packet transmitting apparatus having such a configuration will be described. The average output rate of the packet sequence is set in advance for the output timing determining means 706 as a parameter. The output timer 704 is reset at the reference time, counts the number of frame pulses after the reference time, multiplies the number of frame pulses by the frame pulse period, and outputs the elapsed time from the reference time. The output timing determining means 706 multiplies the elapsed time indicated by the output timer 704 by the output rate of the packet sequence to obtain the data length to be output during the elapsed time.

[0004] The output data amount counter 705 accumulates the data length of packets actually output after the reference time. The output timing determining unit 706 compares the data length to be output with the actually output data length, that is, the output of the output data amount counter 705, and controls the output control so that the difference between the two always falls within a certain range. It instructs means 707 on the output timing of the packet. Output control means 70
7 outputs the packet sequence at the timing specified by the output timing determining means 706.

[0005]

However, in the conventional packet transmitting apparatus, only stream data of a fixed rate format having a constant transmission rate can be transmitted. Therefore, MPEG-2 (Moving Picture Experts
There is a problem that it is difficult to transmit stream data whose transmission rate changes with time, such as video data and audio data encoded in the variable rate format of the Group-2) standard.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is directed to a packet transmission apparatus, a packet transmission method, and a packet transmission method capable of transmitting not only fixed-rate stream data but also variable-rate stream data. An object of the present invention is to provide a packet multiplexing device and to provide an output possible time calculation device that obtains a time at which input to a data buffer of a receiving device can be started as a head time at which output is possible.

[0007]

In order to solve such a problem, the invention of claim 1 of the present application reads out data held in a data source in packet units, and reads the data in packet units via a transmission medium. A packet transmitting apparatus for transmitting to a receiving apparatus at a time, wherein a time at which the data buffer of the receiving apparatus can start inputting the packet data is set as a start time at which the output of the transmitting side is possible, and a packet sequence is input and each packet is transmitted. An output available time calculating means for obtaining an output available start time, a time comparing means for comparing the output available start time obtained by the output available time calculation means with a current time, and a comparison result by the time comparing means. Output control means for controlling the output timing of the packet.

According to a second aspect of the present invention, there is provided a packet transmitting apparatus for reading data held in a data source in packet units and transmitting the data to a receiving apparatus in packet units via a transmission medium. When a time at which the data buffer of the device can start inputting the packet data is set as the output start time on the transmission side, an output time calculation means for inputting a packet sequence and obtaining an output start time of each packet; Time comparison means for comparing the output available head time obtained by the possible time calculation means with the current time; output control means for controlling the output timing of the packet in accordance with the result of comparison by the time comparison means; When the enable signal indicating that the output time has passed the output start time is output by the time comparing means, the output timing of the packet is output. It performed grayed calculations and is characterized by comprising an output timing determining means for instructing the output timing to the output control means.

According to a third aspect of the present invention, there is provided a packet transmitting apparatus for reading data held in a data source in packet units and transmitting the data to a receiving apparatus in packet units via a transmission medium. When a time at which the data buffer of the device can start inputting the packet data is set as the output start time on the transmission side, an output time calculation means for inputting a packet sequence and obtaining an output start time of each packet; A storage unit for temporarily storing the output-capable top time and the data of the input packet obtained by the possible-time calculation unit; a time comparison unit that compares the output-capable top time stored in the storage unit with the current time; Output control for reading packet data from the storage means and controlling the output timing of the packet in accordance with the result of comparison by the time comparison means It is characterized in that it comprises a stage, a.

According to a fourth aspect of the present invention, there is provided a packet transmitting apparatus for reading data held in a data source in packet units and transmitting the data to a receiving apparatus in packet units via a transmission medium. When a time at which the data buffer of the device can start inputting the packet data is set as the output start time on the transmission side, an output time calculation means for inputting a packet sequence and obtaining an output start time of each packet; A storage unit for temporarily storing the output-capable top time and the data of the input packet obtained by the possible-time calculation unit; a time comparison unit that compares the output-capable top time stored in the storage unit with the current time; Output control for reading packet data from the storage means and controlling the output timing of the packet in accordance with the result of comparison by the time comparison means And when an enable signal indicating that the current time has exceeded the output-capable top time is output by the time comparison means, the output timing of the packet is calculated, and the output timing is output to the output control means. And output timing determining means for instructing the output timing.

According to a fifth aspect of the present invention, a first step of inputting a packet in which data of a predetermined amount or less is described as a packet sequence, and a time at which the data buffer of the receiving device can start inputting the packet data, A second step of obtaining an output-capable top time of each packet obtained in the first step, when the output-capable top time of the transmission side is set;
And a third step of comparing the available output start time obtained in the second step with the current time, and controlling the output timing of the packet in accordance with the comparison result. .

According to a sixth aspect of the present invention, there are provided a plurality of sets of the packet transmitting apparatus according to any one of the first to fourth aspects according to the number of channels, and interleaving each packet output from each of the packet transmitting apparatuses. And a packet interleaving means for converting the packet into a single packet sequence.

According to a seventh aspect of the present invention, the time at which the data buffer of the receiving device can start inputting the packet data is determined by:
An output-capable time calculation device that inputs stream data composed of one or more access units for each packet when calculating the output-capable top time on the transmission side, and calculates the output-capable top time of each packet, When the insertion period of data corresponding to the access unit is a slot, a slot counter that outputs a multiplexable start slot number of the packet, and the length of stream data included in the packet is integrated for each access unit, An access unit size counter that outputs the data size of the access unit corresponding to the value indicated by the slot counter, and the length of the stream data included in the packet are integrated, and when the integrated value exceeds a predetermined threshold, First, the slot counter is advanced, and then the access unit It is characterized in that it comprises a buffer simulator to reduce the output of the bets size counter from the current integrated value.

[0014] The invention according to claim 8 of the present application is a communication device, wherein the time at which the data buffer of the receiving device can start inputting the packet data is determined by:
An output-capable time calculation device that inputs stream data composed of one or more access units for each packet when calculating the output-capable top time on the transmission side, and calculates the output-capable top time of each packet, When the insertion period of data corresponding to the access unit is a slot, a slot counter that outputs a multiplexable start slot number of the packet, and the length of stream data included in the packet is integrated for each access unit, An access unit size counter that outputs the data size of the access unit corresponding to the value indicated by the slot counter, and the length of the stream data included in the packet are integrated, and when the integrated value exceeds a predetermined threshold, First, the output of the access unit size counter is Subtracted from calculated value is then those characterized by comprising a buffer simulator advancing the slot counter.

[0015] According to a ninth aspect of the present invention, the time at which the data buffer of the receiving device can start inputting packet data is determined by:
An output-capable time calculation device that inputs stream data composed of one or more access units for each packet when calculating the output-capable top time on the transmission side, and calculates the output-capable top time of each packet, When a slot is a period between decoding times of two adjacent access units whose decoding times are adjacent to each other, the slot has a slot counter for outputting a multiplexable head slot number of the packet and one or more data amount counters. , At least all the data amount counters corresponding to at least the number indicated by the slot counter to the number of the slot whose final time is the decoding time of the access unit to which the stream data included in the packet belongs are included in the packet. The length of the stream data is added to each Count value of the data amount counter corresponding to the number that is indicated, if it exceeds a predetermined threshold, it is characterized in that it comprises a buffer simulator to proceed with the slot counter.

According to a tenth aspect of the present invention, in the packet transmitting device of the first or second aspect, the output possible time calculating means is the output possible time calculating device according to the seventh aspect. is there.

According to an eleventh aspect of the present invention, in the packet transmission device of the first or second aspect, the output possible time calculation means is the output possible time calculation device according to the eighth aspect. is there.

According to a twelfth aspect of the present invention, in the packet transmission device of the first or second aspect, the output possible time calculation means is the output possible time calculation device according to the ninth aspect. is there.

According to a thirteenth aspect of the present invention, in the packet transmission device of the third or fourth aspect, the output possible time calculation means is the output possible time calculation device according to the seventh aspect. is there.

According to a fourteenth aspect of the present invention, in the packet transmission device of the third or fourth aspect, the output possible time calculation means is the output possible time calculation device according to the eighth aspect. is there.

According to a fifteenth aspect of the present invention, in the packet transmission device of the third or fourth aspect, the output possible time calculation means is the output possible time calculation device according to the ninth aspect. is there.

[0022] The invention of claim 16 of the present application is the output possible time calculation device of claim 7, wherein the stream data is video data or audio data.

According to a seventeenth aspect of the present invention, in the output possible time calculating device of the eighth aspect, the stream data is video data or audio data.

[0024] The invention of claim 18 of the present application is the output possible time calculation device of claim 9, wherein the stream data is video data or audio data.

According to a nineteenth aspect of the present invention, in the packet transmission device of the third or fourth aspect, the storage means has a packet data area and an outputable time information area as a recording area of packet sequence management data. The packet data area records packet data, and the output available time information area records the output start time of the packet data.

According to a twentieth aspect of the present invention, in the packet transmitting apparatus according to the thirteenth aspect, the storage means records the output available start time output by the output available time calculation means in the output available time information area. It is characterized by the following.

[0027] According to a twenty-first aspect of the present invention, in the packet transmission device of the fourteenth aspect, the storage means records the outputtable start time output by the outputable time calculation means in the outputable time information area. It is characterized by the following.

According to a twenty-second aspect of the present invention, in the packet transmitting apparatus according to the fifteenth aspect, the accumulating means records the outputable start time output by the outputable time calculating means in the outputable time information area. It is characterized by the following.

[0029]

(Embodiment 1) Hereinafter, a packet transmitting apparatus according to Embodiment 1 of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the packet transmission device according to the present embodiment. As shown in the figure, this packet transmitting apparatus is provided with an output timer 104, an output data amount counter 105, an output timing determining means 106, and an output control means 107 as in the conventional example.

The input terminal 112 is a terminal to which a frame pulse having a predetermined fixed period is input. The possible output time calculating means 101 estimates the amount of data in the data buffer in the receiving device that functions as a video decoder, and calculates the minimum output time of the packet sequence output from the data source via the input terminal 110. It calculates the output start time as a value. The reference clock 103 is reset at a reference time serving as a reference for starting output of an input packet sequence, counts the number of frame pulses input via the input terminal 112 from the reference time, and determines the number of frame pulses and the frame pulse period. By multiplying, the current time is output. The time comparing means 102 compares the current time indicated by the reference clock 103 with the output start time designated by the output possible time calculating means 101. The input terminal 110 is an input terminal for inputting a packet sequence. The output timer 104 counts the number of frame pulses based on the comparison result of the time comparing unit 102,
The elapsed time is output by multiplying the count number by the frame pulse period. The output data amount counter 105 accumulates the data lengths of the packets actually output after the reference time and provides the output timing determination means 106. The output timing determination means 106 controls the output timing of the packet so that the output rate of the packet is equal to or less than a preset maximum transmission rate. The output control means 107 controls the output of the input packet sequence input via the input terminal 110 based on the output timing instructed by the output timing determination means 106, and outputs the packet sequence via the output terminal 111. It is. The output terminal 111 is connected to a receiving device via a network or the like.

The operation of the packet transmitting apparatus configured as described above will be described. In the present embodiment, the packet sequence input via the input terminal 110 is, for example, a video stream compressed in a variable rate format of MPEG-2, a packet of MPEG-2 TS (Transport Stream) format. And output stream data. Note that the maximum output rate of the packet sequence is set in advance for the output timing determining unit 106 as a parameter. This value is set to a sufficiently high value that the video data compressed in the variable rate format can be transmitted without underflow in the data buffer in the receiving device.

First, a packet sequence is supplied from the packet sequence input terminal 110 to the output control means 107 in packet units. As described above, the input packet sequence is video data encoded in a variable rate format. Therefore, it is necessary to adjust the output start timing of each packet in accordance with the video data decode timing so that the data buffer in the receiving device does not overflow.
Therefore, the available output time calculating means 101 obtains the available output start time which is the minimum value of the available output time of the input packet by a method described later in detail.

The reference clock 103 is reset at the reference time and counts the number of frame pulses from the reference time.
The current time is output by multiplying the number of frame pulses by the frame pulse period. In the time comparing means 102, the reference clock 1
03 is compared with the output start time designated by the output possible time calculation means 101. The time comparing means 102 outputs “valid” (enable) to the output timer 104 and the output data amount counter 105 only when the current time has reached the output-capable top time, and the current time becomes the output-capable top time. If not reached, "invalid" is output.

The output timer 104 includes a time comparing means 102
Resets itself immediately after the output of ".times." Changes from "invalid" to "valid", counts the number of frame pulses only while the output of the time comparison means 102 is "valid", and multiplies the counted number by the frame pulse period. By "valid" by
Find the elapsed time since The output timing determining means 106 multiplies the elapsed time indicated by the output timer 104 by the maximum output rate of the packet sequence to obtain a data length that can be output during the elapsed time. Output data amount counter 105
Means that the output of the time comparison means 102 is changed from "invalid" to "valid"
Immediately after it changes to, it resets itself, integrates the data length of the packet actually output after the reset, and outputs the integration result.

The output timing determining means 106 compares the outputable data length obtained previously with the output of the output data amount counter 105 which is the actually output data length, and the difference between the two always falls within a certain range. Thus, the output control unit 107 is instructed on the output timing of the packet. The output control means 107 outputs the packet data at the timing specified by the output timing determination circuit 106. By the above operation, each packet is output to the output possible time calculation means 1.
After the time obtained by 01, the output is performed at a frequency up to the maximum output rate.

(Embodiment 2) Next, a packet transmitting apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of the packet transmission device according to the present embodiment. In this packet transmission device,
As in the first embodiment, the output possible time calculation means 101,
Time comparison means 102, reference clock 103, output timer 10
4. An output data amount counter 105, an output timing determining means 106, and an output control means 107 are provided. The functions of these blocks are the same as those in the first embodiment, and a description thereof will be omitted.

The packet memory 108 has a packet data storage area and an output available time information area, and stores the packet data input via the input terminal 110 and the output available time calculated by the output available time calculation means 101. The time information is temporarily stored, and the packet data is output to the output control unit 107.
, And output possible start time information to the time comparing means 102.

The operation of the packet transmitting apparatus according to the present embodiment is the same as the operation of the packet transmitting apparatus according to the first embodiment except for the following procedure. That is, the packet memory 1
08 is the output possible time calculation means 1 together with each packet data in the packet sequence input from the input terminal 110.
The output available time information of each packet obtained in step 01 is recorded in association with the packet data. At the time of output, packet data and output-capable time head information are sequentially read from the packet memory 108, output-capable head time information is output to the time comparison means 102, and packet data is output to the output control means 107.

Thereafter, similarly to the operation in the first embodiment, the output timing of each packet is determined, and the packet data is output via the output terminal 111. With such a configuration, it is possible to perform in advance the arithmetic processing of the output possible time calculating means 101 having a large processing amount. As a result, it is possible to reduce the number of calculation processes at the time of actual transmission that requires real-time processing.

(Embodiment 3) Next, as Embodiment 3 of the present invention, a packet multiplexing apparatus will be described with reference to FIG. FIG. 3 is a configuration diagram of the packet multiplexing apparatus according to the present embodiment, and shows a configuration when the number of input streams is three as an example. It should be noted that the present invention can be similarly implemented when the number of input streams is other than three. 3, packet transmitting apparatuses 301 and 30 similar to those shown in FIG. 1 or FIG.
2,303 are provided. Packet interleaving means 310 includes packet transmitting devices 301, 302, 30
3. Arrange the packet data output from 3 for each packet,
Insufficiency in the preset output rate is filled with dummy packets, converted into one packet stream of a constant rate, and output via the output terminal 320.

The operation of the packet multiplexing apparatus thus configured will be described. First, the output rate of the packet sequence to be output from the output terminal 320 is set in advance for the packet interleaving means 310. The input packet sequence input from the input terminal 321, 322, 323 of the packet sequence is the packet transmission device 301, 302, respectively.
The output timing is supplied to the packet interleaving unit 310, and the output timing is controlled for each packet by the procedure described in the first or second embodiment. The packet interleaving means 310 arranges these pieces of packet data for each packet, and fills in the shortage of the preset output rate with dummy packets. Then, it outputs one packet sequence at a constant rate.

Packet transmitting devices 301, 302, 303
Can transmit both stream data encoded in the fixed rate format and the stream data encoded in the variable rate format. With the configuration shown in FIG. 3, both the fixed rate format and the variable rate format stream data can be multiplexed. .

Such a packet multiplexing apparatus can be used, for example, in a broadcast station when converting a plurality of fixed-rate or variable-rate video / audio stream data into a fixed-rate packet stream for transmission. it can.
Stream conversion for recording variable-rate stream data such as video / audio data stored in a DVD (Digital Video Disk) on a recording device such as a digital VTR that can always record only a constant-rate stream. It can also be used as a device.

(Embodiment 4) Next, details of the output possible time calculating means (output possible time calculating device) in the packet transmitting apparatus described above will be described below as Embodiments 4 and 5. Output possible time calculation means 1 as described above
01 calculates the temporal change of the amount of data held in the data buffer of the receiving apparatus, and obtains the output-capable top time as the minimum time within a range where the buffer does not overflow. In the following description, a coding unit of input stream data is referred to as an access unit or an AU.
For example, if the stream data is video data, the encoded data corresponding to one video frame or one video field is AU
It is. When a packet sequence including stream data is transmitted from a packet transmitting device to a receiving device, the stream data is accumulated in a data buffer of a video decoder in the receiving device. When the data of each AU is decoded at a predetermined time, it is deleted from the data buffer. This time is called the decoding time of each AU.
Further, a period between the decoding times of two consecutive AUs is called a slot.

In the following embodiment, each slot is given the same number as the AU decoded at the last time of each slot. That is, the period from the decoding time of the (i-1) -th AU to the decoding time of the i-th AU is called a slot i. However, the slot number from the reference time to the decoding time of the first AU is 1. FIG. 6 shows the relationship between such AU numbers and slot numbers.

First, the possible output time calculating means according to the fourth embodiment will be described. FIG. 4 is a configuration diagram of the output possible time calculation means 101A in the present embodiment. In the figure, the data amount detection means 401 is
Is to detect the length of the stream data stored in the payload in the input packet sequence input via the. The AU boundary detection means 402 determines whether or not the first packet of the AU exists in the input packet. The AU counter 404 outputs the currently input AU number based on the detection result of the AU boundary detection means 402.

The decoding time detecting means 403 extracts the AU decoding time from the input packet and records it in the AU decoding time memory 407. The buffer simulator 405 reproduces the transition of the data amount in the data buffer in the receiving device. The AU size counter 406 has a counter for each AU number, and obtains the data amount for each AU based on the output of the data amount detection means 401. The AU decode time memory 407 stores
This is a memory for storing the decoding time for each U, and the decoding time read from this memory is output via the output terminal 113 as the data of the output start time. The slot counter 408 outputs the number of the earliest slot that can output an input packet, that is, the number of the first slot that can be output.

The operation of the output possible time calculating means 101A thus configured will be described with reference to the time charts shown in FIGS. Note that the buffer capacity of the data buffer in the receiving device is set as a threshold value in the buffer simulator 405 in advance. (1); A packet sequence is input for each packet. Less than,
Steps (2) to (5) are repeated for each packet. (2); The AU boundary detecting unit 402 determines whether or not the input packet has the AU head data. If the head data of the AU is detected, the AU
Increment counter 404 by one. In the examples of FIGS. 7 and 8, if the AU boundary detecting unit 402 detects the head data of the AU at the timing 802, the count value indicated by the AU counter changes as 804. The decoding time detection means 403 extracts the AU decoding time from the input packet, and the AU decoding time memory 407
This value is stored as the AU decoding time indicated by the AU counter 404. (3): The data amount detection means 401 detects the length of the stream data stored in the payload of the input packet, and outputs it to the AU size counter 406 and the buffer simulator 405. In the examples of FIGS. 7 and 8, it is assumed that the data amount detection unit 401 outputs the value indicated by 801 for each packet. (4); The AU size counter 406 integrates the output of the data amount detection means 401 with the counter of the number indicated by the AU counter 404. Thus, the AU in the input packet
The amount of data for each is obtained from the AU size counter 406. 7 and 8, the AU size counter 406
The values of the respective counters change as in 806. For example, since the output 804 of the AU counter 404 indicates 1 for packet numbers 1 to 4, the output of the data amount detection means 401 is 40
The data is accumulated in the counter 1 in 6 (811), and finally the data amount 822 of the first AU is obtained. Since the AU counter changes to 2 when the fifth packet is input, the data amount of the fifth and sixth packets is calculated by the counter 2
(812).

(5) The output start time of an input packet is obtained by the following procedure. (I): The buffer simulator 405 integrates the payload data length obtained in (3). (805 in FIGS. 7 and 8) (ii) If the integrated value of the buffer simulator 405 does not exceed a preset threshold, the slot counter 40
Even if the data of the input packet is transmitted in the slot indicated by No. 8, it is determined that the data buffer in the receiving device does not overflow. In this case, the packet can be output after the slot indicated by the slot counter 408, and the value indicated by the slot counter 408 indicates the head slot number at which the input packet can be output. The AU decode time memory 407 outputs the start time of the slot, that is, the decode time of the AU whose number is one less than the slot number indicated by the slot counter 408, thereby obtaining the output start time of the input packet. However, the start time of slot 1 is set to 0, and when the slot counter 408 indicates 1, the AU decode time memory outputs 0. 7 and 8, the count value of the buffer simulator 405 does not exceed the threshold value even when packets of numbers 1 to 6 are input. Therefore, these packets can be output after slot 1, and all of these outputable start times are the start time of slot 1,
That is, it becomes 0. (Iii); If the integrated value of the buffer simulator 405 exceeds the threshold, if the input packet is output in the slot indicated by the slot counter 408, it can be determined that the data buffer in the receiving device overflows. This indicates that no input packet can be output in that slot. Therefore, the following procedure is performed to check the next slot. Here, in the decoder of the receiving apparatus, the AU having the same number as the slot number at the time of moving to the next slot, that is, the last time of the current slot.
Is deleted from the buffer after decoding. Since the AU size is obtained by the AU size counter 406, the size of the AU of the number indicated by the slot counter 408 (that is, the output value of the AU size counter 406) is subtracted from the buffer simulator 405, so that the data in the data buffer of the decoder is obtained. The transition of the data amount can be reproduced. Thereafter, the slot counter 408 is incremented by one, and the process returns to (ii) to check whether output is possible for a new slot. In the examples of FIGS. 7 and 8, when the seventh packet is input, the count value of the buffer simulator 405 exceeds the threshold value. Therefore, this packet cannot be transmitted in slot 1. Therefore, in order to check the slot 2, the data amount 821 of the first AU is subtracted from the count value of the buffer simulator 405, and then the slot counter is advanced by one. Then, since the count value of the buffer simulator 405 becomes equal to or smaller than the threshold value, it is determined that the seventh packet can be output in the slot 2 and thereafter.
The output start time of this packet is the start time of slot 2, that is, the decode time of the first AU.

According to the above procedure, the output start time of the input packet is sequentially obtained. In addition, (iii) of (5)
Then, after the AU size of the number indicated by the slot counter 408 is subtracted from the buffer simulator 405, the counter indicating the AU size of the number becomes unnecessary.
It may be deleted from the size counter 406. FIG.
In the above description, the period from the decoding time of the (i-1) th AU to the decoding time of the i-th AU is referred to as slot i, but from the decoding time of the i-th AU to the decoding time of the (i + 1) -th AU. Can be defined as a slot i. In this case, in the above procedure (iii), after increasing the slot counter 408 first, the buffer simulator 405 sets the AU size counter 406
By performing the process of reducing the output value of the above, the possible output time can be similarly obtained.

(Embodiment 5) Next, as Embodiment 5 of the present invention, an available output time calculating means having a configuration different from that of Embodiment 4 will be described with reference to FIG. FIG. 5 is a block diagram showing a configuration of the output possible time calculation means 101B of the present embodiment. This output possible time calculation means 101
B, like the output possible time calculation means 101A of FIG.
2. Decode time detection means 403, AU counter 40
4. An AU decode time memory 407 and a slot counter 408 are provided. The functions of these blocks are the same as in the fourth embodiment, and a description thereof will not be repeated.

The buffer simulator 505 has a plurality of data amount counters corresponding to the slot numbers, inputs the detection means of the data amount detection means 401, and responds from the number indicated by the slot counter 408 to the number indicated by the AU counter 404. By adding to all the counters, the amount of data that would be accumulated in the data buffer of the receiving device when the input packet was transmitted in each slot is simulated. Slot counter 4
08 outputs the number of the first slot that can be output, which is the number of the earliest slot that can output an input packet.

The operation of the output possible time calculation means 101B thus configured will be described with reference to the time chart shown in FIG. The buffer capacity of the data buffer in the receiving device is set as a threshold value in the buffer simulator 5005 in advance. (1); A packet sequence is input for each packet. Less than,
The procedure of (2) to (6) is repeated for each packet. (2); The AU boundary detection means 402 determines whether or not an AU boundary exists in each of the input packets. When the AU boundary is detected, the AU counter 403 is incremented by one. In the example of FIG. 9, if the AU boundary detection unit 402 detects the head data of the AU at the timing indicated by 902, the count value indicated by the AU counter changes as indicated by 904. (3); The data amount detection means 401 detects the length of the stream data stored in the payload of the input packet, and provides the detection result to the buffer simulator 505. In the example of FIG. 9, it is assumed that the data amount detection unit 401 outputs the value indicated by 901 for each packet. (4); The buffer simulator 505 receives the output of the data amount detection means 401 and adds the data amount to all counters corresponding to the numbers indicated by the slot counter 408 to the numbers indicated by the AU counter 404. At this time, for each data amount counter in the buffer simulator 505, the amount of data that would be accumulated in the data buffer of the receiving device when the input packet was transmitted in that slot is obtained for each slot number. The reason that the output of the data amount detection means 401 is not added to the counter after the number indicated by the AU counter 404 is that the data of the AU decoded before the start time of each slot cannot exist after that time. That's why. Further, since the counters before the number indicated by the slot counter 408 are not used for the determination, the addition of the output of the data amount detecting means 401 is omitted. In the example of FIG. 9, the values of the slot counter and the AU counter are both 1 for the packets of numbers 1 to 4, so that the data amount detection means 40
The output of 1 is added only to the counter 1 of the buffer simulator 505 (911). However, since the AU counter 401 changes to 2 when the fifth packet is input, 5
The data amount of the sixth and sixth packets is determined by the counter 1 (9
11) and the counter 2 (912).
In this way, the counters 1, 2, 3,. . . , Input packets are assigned slot numbers 1, 2, 3,. . . The amount of data that would be stored in the data buffer of the receiving device when the transmission was performed in step (1) is obtained. (5); If the buffer simulator 505
If the data amount counter of the number designated by the slot counter 408 does not exceed a preset threshold value, it is determined that the data buffer in the receiving device does not overflow even if the input packet is transmitted in the slot. In this case, the packet can be output within the slot indicated by the slot counter 408, and the value indicated by the slot counter 408 indicates the head slot number at which the input packet can be output. The AU decode time memory 407
The AU of the start time of this slot, that is, the number obtained by subtracting 1 from the slot number indicated by slot counter 408
, The output start time of the input packet is obtained. However, the start time of slot 1 is set to 0, and when the slot counter 408 indicates 1, the AU decode time memory outputs 0. FIG.
In the example of the above, since the value (911) of the counter 1 does not exceed the threshold value even if the packets of the numbers 1 to 5 are input, these packets can be transmitted after the slot 1, and the output start times of these packets are all Start time of slot 1, that is, 0
Becomes (6); If the buffer simulator 505
When the data amount counter of the number designated by the slot counter 408 exceeds the threshold, it is possible to determine that the data buffer in the receiving apparatus overflows when the input packet is output in the slot. In this case, the input packet cannot be transmitted in that slot. Therefore, the value of the slot counter 408 is increased until the number of the counter in the buffer simulator 505 that is equal to or smaller than the threshold value is indicated. After that, the output available start time of the input packet is obtained by the same procedure as in the case (5). In the example of FIG. 9, when the sixth packet is input, the value (911) of the counter 1 exceeds the threshold value. Therefore, this packet cannot be transmitted in slot 1. Therefore, to check slot 2, the slot counter is advanced by 1, and the counter 2 is referred to. Then, since the count value of the counter 2 is equal to or smaller than the threshold value, it is determined that the sixth packet can be output in the slot 2 and thereafter. Is the decoding time.

In the buffer simulator 505, the data amount counter corresponding to the slot number before the number indicated by the slot counter 408 is not used and may be deleted.

The functions of each block in the packet transmitting device, the packet multiplexing device, and the possible output time calculating means described above can be partially or entirely realized by software. Further, the output timing determining means in the above packet transmitting apparatus determines the packet output timing by comparing the data length of the input packet itself with the data length that can be output and the data length that is actually output. However, the same processing can be performed by comparing the length of stream data stored in the payload of each packet. In that case, the output timing determination means sets the maximum output rate of the stream data, and the output data amount counter accumulates the length of the stream stored in the payload of each packet.

Also, as an example, the input packet sequence has been described as one in which video data compressed in the MPEG-2 variable rate format as stream data is divided into MPEG-2 TS format packets and stored. In addition, in the case of inputting video data variable-rate coded other than MPEG-2 and audio data variable-rate coded as stream data, the MPE
The same can be applied to a packet sequence other than the G-2 TS format. Further, the same configuration can be applied to a case where data such as video / audio data encoded at a fixed rate is input. In addition, the same device can transmit both fixed-rate and variable-rate data.

[0057]

As described above, the first to sixth and tenth aspects of the present invention are described.
According to the inventions of Nos. 15 to 19 and 19 to 22, the advantageous effect that not only the fixed-rate stream data but also the variable-rate stream data can be transmitted is obtained. Also, since the data amount of the data buffer of the receiving device is grasped on the transmitting side, the data buffer on the receiving side does not overflow or underflow.

In particular, according to the third and fourth aspects of the present invention, in addition to the above-described effects, information on the output start time is stored in the storage means together with each packet data. Does not need to be performed in real time.

According to the present invention, packet data of a plurality of channels can be multiplexed and transmitted within a specified transmission band (transfer rate).

According to the present invention, the data amount in the data buffer of the receiving device can be accurately grasped on the transmitting device side. For this reason, even if packet data of a variable rate is transmitted, the failure of the data buffer of the receiving device does not occur.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a packet transmission device according to Embodiment 1 of the present invention.

FIG. 2 is a schematic configuration diagram of a packet transmission device according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a packet multiplexing device according to a third embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an output possible time calculation device according to a fourth embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an output possible time calculation device according to a fifth embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between an AU decode time and a slot.

FIG. 7 is a time chart (No. 1) showing the operation of the fourth embodiment of the present invention.

FIG. 8 is a time chart (No. 2) showing the operation of the fourth embodiment of the present invention.

FIG. 9 is a time chart showing the operation of the fifth embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a conventional packet transmission device.

[Explanation of symbols]

101, 101A, 101B Output possible range calculation means 102 Time comparison means 103 Reference clock 104 Output timer 105 Output data amount counter 106 Output timing determination means 107 Output control means 110, 112, 321, 322, 323 Input terminals 111, 113, 320 Output terminal 108 Packet memory 301, 302, 303 Packet transmitting device 310 Packet interleaving means 401 Data amount detecting means 402 AU boundary detecting means 403 Decoding time detecting means 404 AU counter 405,505 Buffer simulator 406 AU size counter 407 AU decoding time memory 408 Slot counter 410 packet sequence input terminal 801 output value of data amount detection means 401 802 output of AU boundary detection means 402 804 AU card Counter at the count value 811 AU size counter 406 count value 808 slot counter 404 count value 805 buffer simulator 405 of the count value 806 AU size counter 406 of printer 404 1
Count value 812 Counter 2 in AU size counter 406
821 Data amount of the first AU 822 Data amount of the second AU 823 Data amount of the third AU 824 Data amount of the fourth AU 902 Output of the AU boundary detection means 402 904 Count value of the AU counter 404 901 Output value of data amount detection means 401 905 Count value of buffer simulator 505 908 Count value of slot counter 408 911 Count value of counter 1 in buffer simulator 505 912 Count value of counter 2 in buffer simulator 505

Claims (22)

[Claims] 1. A packet transmission device for reading data held in a data source in packet units and transmitting the data to a reception device in packet units via a transmission medium, wherein the data buffer of the reception device is a packet data When the time at which the input can be started is set as the output start time on the transmitting side, the output possible time calculation means for inputting a packet sequence to obtain the output start time for each packet, A time comparing unit that compares the output start time and the current time, and an output control unit that controls the output timing of the packet according to the comparison result of the time comparing unit. Transmission device. 2. A packet transmitting apparatus for reading data held in a data source in packet units and transmitting the data to a receiving apparatus via a transmission medium in packet units, wherein the data buffer of the receiving apparatus is When the time at which the input can be started is set as the output start time on the transmitting side, the output possible time calculation means for inputting a packet sequence to obtain the output start time for each packet, Time comparing means for comparing the output-capable start time with the current time; output control means for controlling the output timing of the packet in accordance with the result of comparison by the time comparing means; and When the enable signal indicating that the time comparison means is output,
An output timing determining unit that calculates output timing of the packet and instructs the output control unit of the output timing. 3. A packet transmission device for reading data held in a data source in packet units and transmitting the data to a reception device in packet units via a transmission medium, wherein the data buffer of the reception device is packet data. When the time at which the input can be started is set as the output start time on the transmitting side, the output possible time calculation means for inputting a packet sequence to obtain the output start time for each packet, Storage means for temporarily storing the output-capable start time and the data of the input packet, a time comparison means for comparing the output-capable start time stored in the storage means with the current time, and reading packet data from the storage means Output control means for controlling the output timing of the packet in accordance with the result of comparison by the time comparison means. Packet transmission device according to claim. 4. A packet transmitting device for reading data held in a data source in packet units and transmitting the data to a receiving device via a transmission medium in packet units, wherein the data buffer of the receiving device is a When the time at which the input can be started is set as the output start time on the transmitting side, the output possible time calculation means for inputting a packet sequence to obtain the output start time for each packet, Storage means for temporarily storing the output-capable start time and the data of the input packet, a time comparison means for comparing the output-capable start time stored in the storage means with the current time, and reading packet data from the storage means Output control means for controlling the output timing of the packet in accordance with the result of the comparison by the time comparison means; When the enable signal indicating that exceeds the available beginning time, output by the time comparison means,
An output timing determining unit that calculates output timing of the packet and instructs the output control unit of the output timing. 5. A first step of inputting a packet in which data of a predetermined amount or less is described as a packet sequence, and a time at which the data buffer of the receiving device can start inputting the packet data is set as an output start time on the transmitting side. When
A second step of obtaining the output available start time of each packet obtained in the first step; and comparing the output available start time obtained in the second step with the current time. A third step of controlling output timing of the packet. 6. A packet transmission device according to claim 1, wherein a plurality of packet transmission devices are provided in accordance with the number of channels, each packet output from each of the packet transmission devices is interleaved, and one packet sequence is provided. A packet multiplexing apparatus comprising a packet interleave means for converting the packet into a packet. 7. When the time at which the data buffer of the receiving device can start inputting packet data is set as the output start time on the transmitting side, stream data composed of one or more access units is input for each packet. An output possible time calculation device for calculating an output possible start time of each packet, wherein a slot for outputting a multiplexable head slot number of the packet when an insertion period of data corresponding to the access unit is a slot. A counter, an access unit size counter that accumulates the length of the stream data included in the packet for each access unit, and outputs a data size of the access unit corresponding to the value indicated by the slot counter; Integrates the length of the stream data, and the integrated value is determined in advance A buffer simulator for advancing the slot counter first, and then subtracting the output of the access unit size counter from the current integrated value when the threshold value is exceeded. apparatus. 8. When the time at which the data buffer of the receiving apparatus can start inputting packet data is set as the output start time on the transmitting side, stream data composed of one or more access units is input for each packet. An output possible time calculation device for calculating an output possible start time of each packet, wherein a slot for outputting a multiplexable head slot number of the packet when an insertion period of data corresponding to the access unit is a slot. A counter, an access unit size counter that accumulates the length of the stream data included in the packet for each access unit, and outputs a data size of the access unit corresponding to the value indicated by the slot counter; Integrates the length of the stream data, and the integrated value is determined in advance A buffer simulator that first subtracts the output of the access unit size counter from the current integrated value and then advances the slot counter when the threshold exceeds the threshold value. apparatus. 9. When the time at which the data buffer of the receiving device can start inputting packet data is set as the output start time on the transmitting side, stream data composed of one or more access units is input for each packet. An output possible time calculation device for calculating an output possible start time of each of the packets, wherein when the time between the decode times of two adjacent access units is a slot, the packet can be multiplexed. And a slot counter having at least one data amount counter, wherein at least the decoding time of the access unit to which the stream data included in the packet belongs from the number indicated by the slot counter has a final time. For all the data amount counters corresponding to the numbers up to A buffer simulator that increments the length of the stream counter included in the packet when the count value of the data amount counter corresponding to the number indicated by the slot counter exceeds a predetermined threshold. And an output possible time calculation device characterized by comprising: 10. The packet transmission device according to claim 1, wherein said output possible time calculation means is the output possible time calculation device according to claim 7. 11. The packet transmission device according to claim 1, wherein said output possible time calculation means is the output possible time calculation device according to claim 8. 12. The packet transmission device according to claim 1, wherein said output possible time calculation means is the output possible time calculation device according to claim 9. 13. The packet transmitting apparatus according to claim 3, wherein said output possible time calculating means is the output possible time calculating apparatus according to claim 7. 14. The packet transmission device according to claim 3, wherein said output possible time calculation means is the output possible time calculation device according to claim 8. 15. The packet transmission device according to claim 3, wherein said output possible time calculation means is the output possible time calculation device according to claim 9. 16. The output available time calculation device according to claim 7, wherein said stream data is video data or audio data. 17. The apparatus according to claim 8, wherein the stream data is video data or audio data. 18. The output available time calculation device according to claim 9, wherein said stream data is video data or audio data. 19. The storage means has a packet data area and an outputable time information area as a recording area of packet sequence management data, and stores packet data in the packet data area.
5. The packet transmitting apparatus according to claim 3, wherein an output start time of the packet data is recorded in the output available time information area. 20. The packet transmitting apparatus according to claim 13, wherein said storage means records the output start time outputted by said output possible time calculation means in said output possible time information area. 21. The packet transmitting apparatus according to claim 14, wherein said storage means records the output start time outputted by said output possible time calculation means in said output possible time information area. 22. The packet transmitting apparatus according to claim 15, wherein said storage means records an output start time output by said output possible time calculation means in said output possible time information area.