JP2000341258A - Communication unit, its method and medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decode respective data encoded according to different system clocks synchronously with each other. SOLUTION: For example, a time stamp PTS replacing section 51 receives a transport packet with a PTS and a program clock reference PCR corresponding to a system time clock STC A added thereto from an encoder 11 and receives a transport packet with a PTS and a PCR corresponding to an STC B added thereto from an encoder 12. The PTS replacing section 51 recovers the STC A on the basis of the PCR corresponding to the STC A and recovers the STC B on the basis of the PCR corresponding to the STC B. The PTS replacing section 51 calculates a new clock corresponding to the STC A with respect to the PTS corresponding to the STC B on the basis of a difference (deviation) between the recovered STC A and STC B and adds the clock value to the transport packet from the encoder 12 in place of the PTS corresponding to the STC B added to the transport packet from the encoder 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus, a method, and a medium, and more particularly, to a communication apparatus, a method, and a medium capable of synchronously reproducing data encoded according to different system clocks. About.

[0002]

2. Description of the Related Art FIG. 1 shows a configuration example of a conventional data transmission system. In this example, the transmitting device 1
In addition to one video data VD, three audio data AD-1 to AD-3 to be reproduced in synchronism with the video data VD (hereinafter, when it is not necessary to distinguish them individually, simply described as audio data AD) . The same applies to other cases). The transmission device 1 encodes and multiplexes the input video data VD and audio data AD to generate a transport stream, and transmits the transport stream on the transmission medium 2.

The receiving device 3 receives the transport stream transmitted via the transmission medium 2 and releases the packetized video data VD and audio data AD contained in the transport stream. And decrypt.

FIG. 2A shows an example of the configuration of the transmitting device 1. The transmission device 1 includes three encoders 11 to 1
3 and a multiplexer 14.
The video data VD and the audio data AD-1 are input to the encoder 11. The video data VD is configured in frame units, for example, as shown in FIG. The encoder 11 first encodes the input video data VD and audio data AD-1 and packetizes them to generate a PES packet. FIG. 3B shows the video data V of FIG.
This shows a PES packet generated from D. In the case of the video data VD, a PES packet (PES packet 1 and PES packet 2 in the example of FIG. 3) is generated for each frame (frame 1 and frame 2 in the example of FIG. 3A). In the case of the audio data AD-1, a PES packet is generated similarly to the video data VD. However, in the case of the audio data AD-1, one generated PES packet includes 3 of the data transmitted in 24 ms. Double data is included. The unit of such PES conversion is freely set.

[0005] The encoder 12 has audio data A
D-2 receives the audio data AD-
3 are input. The encoder 12 and the encoder 13 generate a PES packet from the input audio data AD in the same manner as the encoder 11. In the case of the audio data AD-2 and the audio data AD-3, similarly to the case of the audio data AD-1, one generated PES packet includes data three times as large as the data transmitted in 24 ms. It is.

The encoder 11 also has a 27 MHz system time clock (STC (System Time Clock)) A of its own, as shown in FIG. 3C, at the timing of encoding data and generating a PES packet. Of the PES packet is read and the clock value is set in the header of the PES packet. In the following, the encoder 1
The STC of 1 is described as STCA.

This clock value of the STC set in the header of the PES packet is a so-called time stamp,
It is called S (Presentation Time Stamp) and represents the reproduction time of the data included in the PES packet. In the following, the PTS of the video data VD corresponding to STCA
Is described as PTSAV. In the example of FIG. 3B, as shown in FIG. 3C, the respective data are encoded in the headers of the PES packet 1 and the PES packet 2, and the PES
The PTSAV read at the packetized timing is set. Similarly to the case of the audio data AD-1, the PTS read from the STCA (hereinafter, referred to as the PTSAA of the audio data AD-1 corresponding to the STCA) is set in the header of the generated PES packet. .

[0008] The encoder 12 also has an STC of 27 MHz (hereinafter, this STC is referred to as STCB), reads the PTS from the STCB at the timing of encoding the audio data AD-2 and generating a PES packet. That PTS
Is set in the header of the PES packet. In the following, the PTS of audio data AD-2 corresponding to STCB is described.
Is described as PTSBA. Encoder 13 is also 27MHZ
(Hereinafter referred to as STCC), encodes audio data AD-3, reads a PTS from the STCC at the timing of generating a PES packet, and stores the PTS in the header of the PES packet. Set to. In the following, the PTS of the audio data AD-3 corresponding to the STCC is described as PTSCA. The phases of the STCA of the encoder 11, the STCB of the encoder 12, and the STCC of the encoder 13 are different from each other. That is, these are independent system clocks.

After generating a PES packet of the input video data VD and audio data AD-1, the encoder 11 converts the data of the generated PES packet to 188.
Generate a transport packet by dividing by bytes,
Output to the multiplexer 14. For example, the PES packet 1 shown in FIG. 3B shown in FIG. 4A is divided into four transport packets 1 to 4, as shown in FIG. The header including the PTSAV is included in the transport packet (TS) 1 in the example of FIG. In the following, a transport packet including a PTS, such as transport packet 1, is referred to as a PTS packet.

[0010] The encoder 11 also generates a transport packet at a frequency (1
At 0 times / sec), as shown in FIG. 4C, the clock value of the STCA is read, and the clock value is set in the adaptation_field of the transport packet. The clock value read at this timing is one of the so-called time reference values and is called a PCR (Program Clock Reference), which is referred to when the receiving device 3 reproduces its own STC. You. In the following, STCA
Is described as PCRA. In the following, a transport packet in which the PCR is set to adaptation_field (in the example of FIG. 4, transport packet 5) is described as a PCR packet.

The encoder 12 and the encoder 13 also
Similarly to the encoder 11, a transport packet is generated from the generated PES packet and output to the multiplexer 14, and a predetermined transport packet (PCR packet) from the encoder 12 includes a PCR corresponding to the STCB.
(Hereinafter, this PCR is referred to as PCRB) is set, and in a predetermined transport packet (PCR packet) from the encoder 13, a PCR corresponding to the STCC (hereinafter, this PCR is referred to as PCRC) is set. Have been.

The multiplexer 14 receives the transport packets from the encoder 11, the encoder 12, and the encoder 13, respectively. That is, thereby, the multiplexer 14 outputs the encoded video data VD and audio data AD-1, PTSAV, PTSAA, and P from the encoder 11.
Upon receiving the CRA, the encoder 12 outputs the encoded audio data AD-2, PTSBA, and PCR.
B, and the encoder 13 receives the supply of the encoded audio data AD-3, PTSCA, and PCRC.

The multiplexer 14 multiplexes transport packets input from each of the encoders 11 to 13, generates a transport stream, and transmits the transport stream to the receiving device 3 via the transmission medium 2. When transmitting a plurality of data (in this example, video data VD, audio data AD-1, audio data AD-2, and audio data AD-3), when they are provided as the same service ( For example, when they are played back synchronously, as in this example), only one PCR can be transmitted. Therefore, in this example, the multiplexer 14 sets only the PCRA supplied from the encoder 11 in the PCR packet of the transport stream to be transmitted. Thereby, only the PCRA is transmitted to the receiving device 3. The PTS of the PTS packet of the transport stream is not changed at all.

FIG. 5 shows a PLL provided in the receiving device 3.
2 illustrates a configuration example of a circuit 20. In the subtracter 21 of the PLL circuit 20, in addition to the PCRA set in the PCR packet of the transport stream transmitted from the transmission device 1, the count value input from the counter 25 (the count value of the clock output from the VCO 24). Is entered. Subtractor 21
Calculates the difference between the PCRA and the count value from the counter 25, and outputs the calculation result to the D / A converter 22. The D / A converter 22 converts the calculation result (digital signal) input from the subtractor 21 into an analog signal and outputs the analog signal to a low-pass filter (hereinafter abbreviated as LPF) 23. LPF23 is
The analog signal from the D / A converter 22 is smoothed and VCO
(Voltage controlled oscillator) 24. VCO24 is LPF2
3. Convert the analog signal input from 3 into a digital signal, and use the converted analog signal as a control voltage.
A clock having a frequency corresponding to the control voltage is generated.
That is, as shown in FIG.
The clock generated by O24 is held as a so-called STC (hereinafter, this STC is described as STCR), and the data is reproduced according to the STC. In this case, as described above, the STCR is the PCRA corresponding to the STCA.
The speed is controlled based on the
Synchronize with A.

Here, the reproduction process in the receiving device 3 will be briefly described. In the reproduction process, the clock value of the STCR (actually, STCA) is set to the time stamp of the transmitted data (in this case, PTS ) Is started when it matches. From this, for example, encoded video data VD and audio data AD-1
Both indicate the timing of reproduction output by PTSAV and PTSAA corresponding to STCA, so that they are reproduced synchronously. When the video data VD is a video of a movie and the audio data AD-1 is its Japanese audio, the video and the Japanese audio are synchronized (so that the video and the Japanese audio match). Will be played. Further, as described above, the clock value of STCR is P
Since the reproduction is started after waiting for a match with the TS, the data to be reproduced is temporarily stored in a buffer 30 as shown in FIG. 6, and is read from there at the timing of the reproduction. In this case, since the STCR is controlled to synchronize with the STCA, the video data VD and the audio data AD temporarily stored in the buffer 30 are appropriately read therefrom, and thereby, The buffer 30 does not fail.

[0016]

On the other hand, the encoded audio data AD-2 has a different phase from STCA.
Since the playback output timing is indicated by the PTSBA corresponding to the CB, the audio data AD-2 includes the STCA
Are not reproduced in synchronization with the video data VD whose reproduction output timing is indicated by the PTSAV corresponding to. For example, if the audio data AD-2 is the audio data AD
In the case where the Japanese voice of -1 is a dubbed voice in English, the video of the video data VD and the English voice are reproduced with a shift.

Further, since the STCR and STCB of the receiving device 3 are not synchronized, the audio data AD-1 temporarily stored in the buffer 30 is not read out from the buffer at an appropriate timing, and the buffer 30 breaks down. For example, STC
If the phase of R lags behind that of STCB, STCR becomes PT
The timing corresponding to SBA (timing at which reproduction is started) is later than the timing at the time of encoding, and the reading from the buffer 30 is delayed. Eventually, in such a case, an overflow occurs in the buffer 30. Conversely, when the phase of STCR is ahead of that of STCB, the timing at which STCR matches PTSBA is earlier than the timing at the time of encoding, and reading from buffer 30 is earlier. Eventually, in such a case, an underflow occurs in the buffer 30.

As with the audio data AD-2, it is difficult to reproduce the audio data AD-3 in synchronization with the video data VD, and the buffer 30 is broken.

After all, the data to be reproduced in synchronization is
When encoded by independent STCs, it is difficult to reproduce them synchronously, and there is a problem that a buffer for temporarily storing the data is broken. The present invention has been made in view of such circumstances, and reproduces data encoded according to independent system clocks in synchronization with each other, and does not break down a buffer in which the data is temporarily stored. Is to do so.

[0020]

According to the first aspect of the present invention, there is provided a communication apparatus comprising: first receiving means for receiving first data to which a first time stamp corresponding to a first clock is added; First clock recovery means for recovering a first clock corresponding to a first time stamp added to the first data received by the first reception means, and a second time corresponding to the second clock Second receiving means for receiving the second data to which the stamp has been added, and reproducing a second clock corresponding to the second time stamp added to the second data received by the second receiving means. A second clock regenerating unit, a calculating unit for calculating a difference between the first clock regenerated by the first clock regenerating unit and a second clock reproduced by the second clock regenerating unit, Calculated by A calculation result of the, based on the second time stamp added to the second data, the first
Generating means for generating a third time stamp corresponding to the clock of (i), and adding means for adding the third time stamp generated by the generating means to the second data instead of the second time stamp. It is characterized by having.

According to a second aspect of the present invention, in the communication method, a first time stamp corresponding to a first clock is added.
A first receiving step of receiving the first data and a first clock recovering step of recovering a first clock corresponding to a first time stamp added to the first data received in the first receiving step A second receiving step of receiving second data to which a second time stamp corresponding to a second clock is added, and a second receiving step of adding second data to the second data received in the second receiving step. A second clock recovery step for recovering a second clock corresponding to the second time stamp, a first clock recovered in the first clock recovery step, and a second clock recovered in the second clock recovery step. Calculating a clock difference between the first and second clocks based on a calculation result calculated in the calculation step and a second time stamp added to the second data.
A generating step of generating a third time stamp corresponding to the clock of (i), and an adding step of adding the third time stamp generated in the generating step to the second data instead of the second time stamp. It is characterized by including.

According to a third aspect of the present invention, a medium is received in a first receiving step of receiving first data to which a first time stamp corresponding to a first clock is added, and a first receiving step. A first clock reproducing step of reproducing a first clock corresponding to a first time stamp added to the first data, and a second clock reproducing step of adding a second time stamp corresponding to a second clock. A second receiving step of receiving the second data, and a second clock recovering step of recovering a second clock corresponding to the second time stamp added to the second data received in the second receiving step A calculating step of calculating a difference between the first clock reproduced in the first clock reproducing step and the second clock reproduced in the second clock reproducing step;
A generating step of generating a third time stamp corresponding to the first clock based on the calculation result calculated in the calculating step and a second time stamp added to the second data; An adding step of adding the obtained third time stamp to the second data instead of the second time stamp.

In the communication device according to the first aspect, the communication method according to the second aspect, and the medium according to the third aspect, the first time stamp corresponding to the first clock is added to the first time stamp. Of the received first data, the first clock corresponding to the first time stamp added to the received first data is reproduced, and the second clock added with the second time stamp corresponding to the second clock is reproduced. 2 data is received, a second clock corresponding to a second time stamp added to the received second data is reproduced, and a reproduced first clock and a reproduced second clock are reproduced. Is calculated, and a third time stamp corresponding to the first clock is generated based on the calculated result and the second time stamp added to the second data. 3 time Stamp is in place of the second time stamp, it is appended to the second data.

According to a fourth aspect of the present invention, in the communication apparatus, a first adding means for adding a time stamp corresponding to a predetermined clock to the first data, and a time stamp corresponding to the clock to the second data. It is characterized by comprising a second adding means and a supply means for supplying the first clock in the adding means to the second adding means.

According to the communication method of the present invention, a first adding step of adding a time stamp corresponding to a predetermined clock to the first data, and adding a time stamp corresponding to the clock to the second data. It is characterized by including a second adding step and a supplying step of supplying the first clock in the first adding step to the second adding step.

According to a sixth aspect of the present invention, in the medium, a first adding step of adding a time stamp corresponding to a predetermined clock to the first data, and a second adding step of adding a time stamp corresponding to the clock to the second data. 2, and a supply step of supplying the first clock in the first addition step to the second addition step.

In the communication device according to the fourth aspect, the communication method according to the fifth aspect, and the medium according to the sixth aspect, a time stamp corresponding to a predetermined clock is added to the first data, Is added to the second data.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. In order to clarify the correspondence between each means of the invention described in the claims and the following embodiments, each means is described. When the features of the present invention are described by adding the corresponding embodiment (however, an example) in parentheses after the parentheses, the result is as follows. However, of course, this description does not mean that each means is limited to those described.

FIG. 7 shows a configuration example of a data transmission system to which the present invention is applied. This data transmission system includes a transmission device 41 instead of the transmission device 1 of FIG. As in the case of the example of FIG. 2, the transmitting device 41 has one video data VD and the video data VD
Audio data AD to be reproduced in synchronization with
It is assumed that -1 to AD-3 are input. Transmission device 1
Encodes and multiplexes the input video data VD and audio data AD, generates a transport stream, and transmits the transport stream on the transmission medium 2.

FIG. 8 shows a configuration example of the transmission device 41. In the following, referring to FIG.
1 will be described, and its operation will also be described. This transmission device includes a PT between the encoders 11 to 13 of the transmission device 1 shown in FIG.
An S replacement unit 51 is provided. Also in this example, video data VD and audio data AD-1 are input to the encoder 11, audio data AD-2 is input to the encoder 12, and audio data AD-3 is input to the encoder 13. . That is, the encoder 11 generates a transport packet generated from the video data VD and the audio data AD-1, and outputs the transport packet to the PTS reordering unit 51. The transport packet includes, in addition to the one containing the encoded video data VD and the audio data AD-1, a PTS packet containing PTSAV, a PTS packet containing PTSAA, and a PCR packet having PCRA set in the header. I have.

The encoder 12 outputs audio data AD
-2, and generates a transport packet and outputs it to the PTS reordering unit 51. The transport packet includes a PTS packet including PTSBA and a PCR packet in which a PCRB is set in a header, in addition to a packet including the encoded audio data AD-2. Encoder 13
Generates a transport packet from the audio data AD-3 and outputs it to the PTS reordering unit 51. The transport packet includes a PTS packet including PTSCA and a PCR packet in which a PCRC is set in a header, in addition to a packet including the encoded audio data AD-3.

FIG. 9 shows a configuration example of the PTS reordering unit 51. In the following, with reference to FIG. 9, the configuration of the PTS reordering unit 51 will be described, and the operation thereof will also be described. The PTS replacement unit 51 includes a PTS replacement unit 61 and a PT
An S replacement unit 62 is provided. Introduction PTS replacement unit 61
Will be described. The transport packet from the encoder 11 is input to the STC reproducing circuit 71 of the PTS reordering unit 61.

The STC reproducing circuit 71 has, for example, a PLL circuit (not shown) having the same configuration as the PLL circuit 20 shown in FIG. That is, the STC reproducing circuit 71 extracts the PCRA from the PCR packet of the transport packet from the encoder 11, reproduces the clock (STCA) based on the extracted PCRA, and outputs the clock (STCA) to the subtracter 72.

The transport packet from the encoder 12 is input to the STC reproducing circuit 73. The STC reproducing circuit 73 has a function similar to that of the STC reproducing circuit 71, extracts a PCR (PCRB in this example) from a PCR packet of an input transport packet, and extracts the extracted PC.
The clock (STCB) is reproduced based on the RB, and the subtracter 7
Output to 2.

The subtractor 72 outputs the STC from the STC reproducing circuit 71.
A and the clock value of STCB from the STC reproducing circuit 73 are read as needed, the difference between them (STCA-STCB) is calculated, and the calculation result is output to the adder 74. That is, STCA and STC
The phase shift of B is determined.

The transport packet from the encoder 12 input to the STC reproduction circuit 73 is also input to the PTS extraction circuit 75. The PTS extraction circuit 75 extracts a PTS (in this case, PTSBA) from the PTS packet of the transport packet from the encoder 12, and outputs the PTS to the adder 74. The PTS extraction circuit 75 also outputs a predetermined PTS replacement signal to the PTS replacement circuit 76 at the timing when the PTS is extracted.

The adder 74 adds the PTSBA from the PTS extraction circuit 75 to the calculation result (= STCA-STCB) from the subtractor 72.
And outputs the addition result to the PTS replacement circuit 76. As a result, PTSBA becomes PTS (PTSAV) corresponding to STCA. The transport packet from the encoder 12 is input to the PTS replacement circuit 76. PTS replacement circuit 7
The adder 74 adds a transport packet input at the timing when the PTS replacement signal is input from the PTS extraction circuit 75, that is, the PTSBV included in the PTS packet to the adder 74.
And outputs the result to the multiplexer 14 instead of the calculation result (PTSAV).

The transport packet from the encoder 11 is input to the buffer 77, and the STC reproduction circuit 71
After that, the signal is delayed by the time required for the processing in the PTS replacement circuit 76 (or the time required for the processing in the PTS replacement unit 62 described later) and output to the multiplexer 13. As described above, in the PTS change unit 61, the PTSBA of the PTS packet of the transport packet from the encoder 12 is changed to the PTSAV corresponding to the STCA. Since no processing has been performed on the PCR packet, PCRB is set as it is in this PCR packet.

Next, the PTS reordering section 62 will be described. S
The transport packet from the encoder 13 is input to the TC reproducing circuit 81. The STC reproducing circuit 81 has the same function as the STC reproducing circuit 71 and the STC reproducing circuit 73 of the PTS reordering unit 61, and has the PCR set in the PCR packet of the input transport packet (in this case, PC
RC), and a clock (STCC) is reproduced based on the extracted PCRC and output to the subtractor 82.

The subtractor 82 receives the S from the STC reproduction circuit 81
In addition to the TCC, the STC from the STC playback circuit 71 of the PTS reordering unit 61
A is input. The subtractor 82 receives the input STCA and STC
The difference from C (= STCA-STCC) is calculated, and the calculation result is output to the adder 83. Adder 83 to PTS replacement circuit 85
Has the same functions as the adder 74 to the PTS replacement circuit 76 of the PTS replacement unit 61, and thus a detailed description thereof is omitted. However, the PTS replacement circuit 85 converts the PTSCA of the PTS packet into The adder 83 replaces the PTSCA with the clock value (PTSAA) corresponding to the STCA and outputs it to the multiplexer 14.

As described above, in the PTS change section 62, the PTSCA of the PTS packet of the transport packet from the encoder 13 is changed to the PTSAV corresponding to the STCA. Since no processing is performed on the PCR packet, the PCRC is set as it is in this PCR packet.

Referring back to FIG. 8, the multiplexer 14 multiplexes the input transport packet from the PTS reordering unit 51 and transmits the multiplexed packet to the receiving device 3 via the transmission medium 2. In the packet, P
The PCR of the encoder 11 input via the TS reordering unit 51
Only the PCRA set in the packet is set.

As described above, the transmitting device 41
A PTS change unit 51 for changing S is provided.

In this case, the receiving device 3
Since the PCRA is input to the PLL circuit 20 in the same manner as in the example of FIG. 2, the PLL circuit 20 has an STCR that is reproduced based on the PCRA and is synchronized with the STCA, and performs data reproduction processing according to the STCR. In the case of this example, in addition to the encoded audio data AD-1, the encoded audio data AD-2 and the audio data AD-3 also, like the encoded video data VD, correspond to the PTCA corresponding to the STCA.
Since the playback timing is indicated by SAA, for example, video data VD and audio data AD
-2, video data VD and audio data AD-3
Are played synchronously. The audio data AD-2 and the audio data AD-3 are read out from the buffer 30 at appropriate timing, so that the buffer 30 does not fail.

As described above, data encoded with different clocks (STCs) are also reproduced synchronously,
Also, the buffers in which they are temporarily stored do not break down.

In the above description, the case where three encoders 11 to 13 are provided in the transmission device 41 has been described as an example. However, in practice, an encoder that only processes data for ten channels may be provided. it can. For example, ten encoders for processing data for one channel may be provided, or only ten channels of encoders for processing data for a plurality of channels may be provided.

In the above description, the PTS replacement circuit 51
Has been described as an example in the case of being provided inside the transmission device 41, but it is also possible to use it, for example, by attaching it to the transmission device 1 of FIG.

FIG. 10 shows a configuration example of the transmission device 41. The transmission device 41 includes three encoders 91 to 9
3 and a multiplexer 94.
The video data VD and the audio data AD-1 are input to the encoder 91. The encoder 91 receives the input video data VD and audio data AD-
1 is executed in the same manner as the encoder 11 shown in FIGS. That is, the encoder 91
A transport packet generated from the video data VD and the audio data AD-1 is generated and output to the multiplexer 94. The encoder 91 performs the same processing as the encoder 11, and also has its own STC.
A is output to the encoder 92 and the encoder 93.

The encoder 92 has audio data A
D-2 is input. The encoder 92 performs the same processing as the encoder 12 shown in FIGS. 2 and 8 on the input audio data AD-2. That is, the encoder 92 generates a transport packet from the audio data AD-2,
In this case, unlike the encoder 12, the encoder 92 does not have its own STCB, and performs processing according to the STCA supplied from the encoder 91. That is, the PTS packet of the transport packet generated by the encoder 92 includes the PT corresponding to the STCA.
SAA is included, and the PCR packet corresponds to STCA.
PCRA is set.

The encoder 93 has audio data A
D-3 is input. The encoder 93 executes the same processing as the encoder 13 shown in FIGS. 2 and 8 on the input audio data AD-3. That is, the encoder 93 generates a transport packet from the audio data AD-3,
In this case, unlike the encoder 13, the encoder 93 does not have its own STCC, and performs processing according to the STCA supplied from the encoder 91. That is, the PTS packet of the transport packet generated by the encoder 93 includes the PT corresponding to the STCA.
SAA is included, and the PCR packet corresponds to STCA.
PCRA is set.

The multiplexer 94 includes an encoder 91,
The transport packets input from each of the encoder 92 and the encoder 93 are multiplexed to generate a transport stream. In this case, unlike the multiplexer 14 shown in FIG. 2, the PCR is not replaced.

That is, in this case, the video data VD, the audio data AD-1, the audio data AD-2, and the audio data AD-3 are the same ST.
Since the encoding is performed based on C (in this case, STCA), PTS and PCR corresponding to STCA are added.
That is, they are reproduced in the receiving device 3 in synchronization with each other. Further, since they are appropriately read from the buffer 30, the buffer 30 does not break down.

In the present specification, the term “system” means an entire device including a plurality of devices, means, and the like.

Next, with reference to FIG. 11, a description will be given of a medium used to install a program for executing the above-described series of processes in a decoder and to make the program executable by the decoder.

As shown in FIG. 11A, the program can be provided to the user in a state where the program is installed in a hard disk 102 or a semiconductor memory 103 as a recording medium built in the decoder 101 in advance.

Alternatively, the program is executed as shown in FIG.
As shown in (B), the floppy disk 111 and the CD-R
OM (Compact Disk-Read Only Disk) 112, MO (Magn
eto-Optical) Disc 113, DVD (Digital Versatile)
Disk) 114, magnetic disk 115, semiconductor memory 11
6, etc., temporarily or permanently stored in a recording medium,
It can be provided as package software.

Further, as shown in FIG. 11C, the program is wirelessly transferred from a download site 121 to a decoder 123 via an artificial satellite 122 for digital satellite broadcasting, or a local area network or the Internet. Via the network 131, the data is transferred to the decoder 123 by wire, and in the decoder 123,
It can be stored in a built-in hard disk or the like.

[0058]

According to the communication device described in claim 1, the communication method described in claim 2, and the medium described in claim 3, the first clock and the second clock are reproduced. Therefore, a third time stamp corresponding to the first clock can be generated based on a difference between the first clock and the second clock and a second time stamp corresponding to the second clock.

According to the communication device of the fourth aspect, the communication method of the fifth aspect, and the medium of the sixth aspect,
Since the first clock is supplied to the second adding unit, the second adding unit can add a time stamp corresponding to the same clock as that of the first adding unit to the second data.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a conventional data transmission system.

FIG. 2 is a diagram illustrating a configuration example of a transmission device 1 of FIG. 1;

FIG. 3 is a diagram illustrating a PTS.

FIG. 4 is a diagram for explaining PCR.

FIG. 5 is a diagram illustrating a configuration example of a PLL circuit 20.

FIG. 6 is a diagram for explaining a buffer 30;

FIG. 7 is a diagram illustrating a configuration example of a data transmission system to which the present invention has been applied.

8 is a diagram illustrating a configuration example of a transmission device 41 in FIG. 7;

9 is a diagram illustrating a configuration example of a PTS reordering unit 51 in FIG. 8;

FIG. 10 is a diagram illustrating another configuration example of the transmission device 41 of FIG. 7;

FIG. 11 is a diagram illustrating a medium.

[Explanation of symbols]

1 transmitting device, 2 transmission medium, 3 receiving device, 1
1 encoder, 12 encoders, 13 encoders, 14 multiplexers, 21 subtracters, 2
2 D / A converter, 23 LPF, 24 VCO, 30
Buffer, 41 transmission device, 51 PTS replacement unit,
61 PTS replacement section, 62 PTS replacement section, 71 STC regeneration circuit, 72 subtracter, 73 STC regeneration circuit, 7
4 adder, 75 PTS extraction circuit, 76 PTS replacement circuit, 77 buffer, 81 STC regeneration circuit, 82 subtractor, 83 adder, 84 PTS extraction circuit, 85P
TS replacement circuit

Claims (6)

[Claims] 1. A first receiving means for receiving first data to which a first time stamp corresponding to a first clock has been added, and said first data received by said first receiving means. A first clock regenerating unit for regenerating the first clock corresponding to the first time stamp added to the second clock; and a second data to which a second time stamp corresponding to a second clock is added. Second receiving means for receiving, and second clock recovery for recovering the second clock corresponding to the second time stamp added to the second data received by the second receiving means Means, and the first clock reproduced by the first clock reproducing means.
And a calculating means for calculating a difference between the second clock and the second clock reproduced by the second clock reproducing means; a calculation result calculated by the calculating means; Generating means for generating a third time stamp corresponding to the first clock on the basis of a second time stamp; and converting the third time stamp generated by the generating means into the second time stamp A communication unit that adds the second data to the second data. 2. A first receiving step of receiving first data to which a first time stamp corresponding to a first clock is added, and the first data received in the first receiving step. A first clock recovery step of recovering the first clock corresponding to the first time stamp added to the second clock; and a second data to which a second time stamp corresponding to a second clock is added. A second receiving step for receiving; and a second clock recovery for recovering the second clock corresponding to the second time stamp added to the second data received in the second receiving step. And the first clock recovery step performed by the first clock recovery step.
And a calculation step of calculating a difference between the second clock recovered in the second clock recovery step, a calculation result calculated in the calculation step, and a calculation result added to the second data. Generating a third timestamp corresponding to the first clock based on a second timestamp; replacing the third timestamp generated in the generating step with the second timestamp Instead of adding to the second data. 3. A first receiving step of receiving first data to which a first time stamp corresponding to a first clock has been added, and the first data received in the first receiving step. A first clock recovery step of recovering the first clock corresponding to the first time stamp added to the second clock; and a second data to which a second time stamp corresponding to a second clock is added. A second receiving step for receiving; and a second clock recovery for recovering the second clock corresponding to the second time stamp added to the second data received in the second receiving step. And the first clock recovery step performed by the first clock recovery step.
And a calculation step of calculating a difference between the second clock recovered in the second clock recovery step, a calculation result calculated in the calculation step, and a calculation result added to the second data. Generating a third timestamp corresponding to the first clock based on a second timestamp; replacing the third timestamp generated in the generating step with the second timestamp A medium for causing a computer to execute a program, the method further comprising: an adding step of adding the second data to the second data. 4. A first adding means for adding a time stamp corresponding to a predetermined clock to the first data, a second adding means for adding a time stamp corresponding to the clock to the second data, The clock in the first adding means is referred to as the second clock.
And a supply means for supplying the additional means. 5. A first adding step of adding a time stamp corresponding to a predetermined clock to first data, a second adding step of adding a time stamp corresponding to the clock to second data, A supplying step of supplying the first clock in the first adding step to the second adding step. 6. A first adding step of adding a time stamp corresponding to a predetermined clock to first data, a second adding step of adding a time stamp corresponding to the clock to second data, A medium for causing a computer to execute a program, comprising: a supply step of supplying the first clock in the first addition step to the second addition step.