JP2001177568A - Stream multiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a stream multiplexer performing stream multiplexing and PCR correction with a simple configuration. SOLUTION: An input time measuring part 12 measures the input time of each packet included in an input stream. An input controlling part 13 writes each packet data and the input time included in the input stream into buffer memory 18. An output order deciding means 16 decides the output order of the packets written in the memory 18. A PCR correcting means 17 rewrites a PCR by using the input time and an output time stored in the buffer memory 11 when the PCR is included in the packet whose output order is decided by the means 16. An output controlling part 14 reads and outputs packet data from the memory 18 in the order decided by the means 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stream multiplexing apparatus having a function of correcting PCR contained in a multiplexed stream when multiplexing and transmitting a plurality of streams.

[0002]

2. Description of the Related Art In a CS broadcast or a digital CATV broadcast, a plurality of programs are multiplexed and broadcast on one channel. That is, the broadcasting station encodes the video / audio signal of each program according to the MPEG2 standard.
Then, a transport stream (hereinafter, referred to as a stream) is generated. Then, the broadcasting station multiplexes the plurality of obtained streams to generate one multiplexed stream, and transmits the multiplexed stream to the receiver via the transmission path. The recipient side
The transmitted multiplexed stream is received, and a stream corresponding to a desired program is extracted therefrom and decoded (decoded). Then, the obtained video / audio signal is reproduced through a television or the like.

[0003] In the following, a device provided on a broadcast station side for encoding a video / audio signal as described above is called an encoder, and a device for multiplexing output streams of a plurality of encoders is called a stream multiplexing device. . A device provided on the receiver side for receiving a multiplexed stream from a broadcasting station and extracting and decoding a specific stream is called a decoder.

FIG. 4 shows an example of the configuration of a conventional CS broadcasting system, showing a basic configuration of a broadcasting station side and a subscriber side. In a specific packet (188 bytes) constituting the stream, the step of the system clock on the encoder side and the system
In order to match the clock steps with each other, a program clock reference (hereinafter referred to as PCR
Is inserted. Such a packet is called a PCR packet. If there is a step lag between the system clock on the encoder side and the system clock on the decoder side, that is, a lag in the progress of time, the decoding processing in the decoder will be hindered. As a result, troubles such as disorder of the reproduced image occur on the subscriber side. In order to prevent such troubles, the PCR is periodically transmitted.

Each encoder 50 attaches its own system clock value as a PCR to a PCR packet when transmitting a PCR packet which is a specific packet in the output stream. One PCR packet is included in the stream for every predetermined number of packets.
The decoder 54 corrects its own system clock with reference to the PCR attached to the received PCR packet. That is, the system clock of the encoder 50 is made to match the system clock of the encoder 50 side.

Therefore, in the stream multiplexing device 51,
When a plurality of streams are multiplexed and transmitted, it is necessary to perform a correction process on the PCR included in the multiplexed stream to be transmitted and attached by each encoder 50.

[0007]

In the above-described conventional stream multiplexing apparatus 51, data of a plurality of input streams are stored in buffer memories provided individually.
Therefore, the conventional stream multiplexing device 51 requires a buffer memory of the number equal to the number of input streams, that is, the number of multiplexing. As a result, there is a problem that the device scale becomes large, especially when the number of multiplexing increases.

The present invention has been made in view of such conventional problems, and does not provide a buffer memory for each input stream, and performs stream multiplexing and PCR correction with a simple configuration. It is an object of the present invention to realize a stream multiplexing device capable of performing such operations.

[0009]

The invention according to claim 1 of the present application is a stream multiplexing apparatus for multiplexing a plurality of input streams and outputting the multiplexed streams, and measures the input time of each input packet in each input stream. Input time measuring means, output time measuring means for measuring an output time of each output packet in the multiplexed stream, an input queue for temporarily holding the input packet and its input time, and the output packet address and its output time A buffer memory having an output queue for temporarily holding the packet, an output order determining means for determining an output order of each packet stored in an input queue of the buffer memory, and a packet whose output order is determined by the output order determining means. Rewrites the PCR if it contains a PCR (Program Clock Reference) It is characterized in that it comprises a PCR correction means.

According to a second aspect of the present invention, in the stream multiplexing device of the first aspect, the buffer memory is connected to the input time measuring means and the output time measuring means via an input / output bus. Is connected to the output order determination means and the PCR correction means through the, write and read each packet to the buffer memory, and write the input time and the output time,
It is characterized by using the input / output bus.

According to a third aspect of the present invention, in the stream multiplexing apparatus of the first aspect, the PCR correction means determines whether the input time of the specific packet stored in the buffer memory is earlier than the input time of the specific packet. The PCR is rewritten using the output time of the output packet.

According to a fourth aspect of the present invention, in the stream multiplexing apparatus of the first aspect, the output order determining means determines an input time of each packet stored in the buffer memory and an output time of each packet already output. The output order is determined using the output time.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A stream multiplexing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the stream multiplexing apparatus according to the present embodiment. This stream multiplexing apparatus includes a plurality of input units 10A, 10B,... 10N and one output unit 1 for multiplexing a plurality of input streams.
1 is provided. The input unit 10A includes an input time measurement unit 12 and an input control unit 13. Input unit 10B-1
0N has the same configuration as the input unit 10A. Each input unit 10
A to 10N are connected to the output unit 11 and the buffer memory 18 via the input / output bus 19.

The input time measuring unit 12 of the input unit 10A measures the time at which each packet of the input stream is input to the input unit 10A. The input control unit 13 writes each packet data of the input stream and the input time measured by the input time measuring unit 12 into a part of the buffer memory 18.

The buffer memory 18 is a memory having a plurality of input queues for each input stream and one output queue. The input queue is a data array that stores the packet data, the input time and the input flag of the packet. The output queue is a data array that stores the addresses in the input queue of the P packets whose output order has been determined, and the output times and output flags of the packets. As shown in FIG. 2, the buffer memory 18 has a plurality of input queues and a data area of one output queue from the upper address to the lower address.
The buffer memory 18 having such a data area is
The output order determining means 16 and the PCR correcting means 17 are connected via the control bus 20.

The output unit 11 shown in FIG.
4 and an output time measuring unit 15 are provided. The output control unit 14 reads an address recorded in the output queue of the buffer memory 18, reads out packet data indicated by the address from the input queue, and outputs the packet data. The output time measuring unit 15 measures the time at which the head of each output packet is actually output from the stream multiplexer. The output order determining means 16 determines the output order of each output packet in a plurality of streams, and includes the number of broadcast channels, the bit rate of each input stream, and the DTS (decoding / decoding) of each packet data.
Time stamp), the bit rate of the output stream, and the like. The output order of the packets determined here is recorded in the output queue.

The PCR correction means 17 includes a buffer memory 1
The correction value of the PCR is calculated on the basis of the input time and the output time of each packet held in No. 8 to generate a corrected PCR. The output time refers to the output time of P packets already output in the output queue because the output time is stored in the output queue. FIG. 3 is a time chart showing the principle of PCR correction in the PCR correction means 17. FIG. 3 shows the input time Tin of the PCR packet.
FIG. 3A shows the output time Tout of the PCR packet using the same time axis as shown in FIG.

As shown in the figure, the PCR is located at the position of the sixth byte from the head position of the PCR packet, that is, P on the time axis.
It is inserted at a position x time from the head position of the CR packet. One such PCR packet is periodically generated for each of a plurality of packets, and the output time Tout of the PCR packet is delayed by the time τ from the input time Tin due to multiplexing of the packets. Assuming that the number of packets that can be recorded in the output queue of FIG. 2 is P, as shown in FIG. 3B, a packet positioned Q (Q <P) prior to the PCR packet, for example, two packets before, is monitored. To This packet is output from the stream multiplexing device shown in FIG. 1 at a time T'out earlier by a time y than the output time Tout.
The output time T′out is, as described above, before the time when the PCR packet is output, as described above.
Is recorded in the output queue, and can be determined by referring to this output queue. Since the time y can be predicted or measured before the output of the PCR packet, the delay time τ is obtained using the following equation. τ = T'out−Tin + y

Normally, the output time T of the PCR packet
After measuring out, the delay time is known as τ. However, as shown in FIG. 3 (c), generating the corrected PCR within a short time x from the output time Tout has some time margin. It can be said that there is no. Therefore, in the present embodiment, a corrected PCR is generated with a time y longer than the time x. The PCR can be corrected by adding the delay time τ thus obtained to the PCR value at the time of input.

The operation of the stream multiplexing apparatus having the above configuration will be described. Input time measurement unit 12
Measures the time when each packet data of the input stream was input to the stream multiplexer. Input control unit 13
Writes the packet data of the input stream and the input time measured by the input time measuring unit 12 into the input queue shown in FIG. 2, and further sets the input flag to 1. The packet data, the input time, and the input flag are sequentially written from the head of the array forming the input queue. If there are N packet data recording areas in one input queue, the end of the array, that is, if the Nth recording area is reached, return to the top of the array and repeat the above procedure. In this case, the previous data is overwritten.

The output order determining means 16 determines the output order of each output packet in a plurality of streams based on the number of broadcast channels, the bit rate of each input stream, the DTS of each packet data, the bit rate of an output stream, and the like. Record the packet output order in the output queue. In the steady state, the output order determining means 16 can determine the order to be output in the future by referring to the output order of each packet already output from the stream multiplexer and recorded in the output queue. .
Basically, in the same input stream, the output order is determined in the same order as the input time.

The output control section 14 reads the address determined by the output order determining means 16 and recorded in the output queue, and reads and outputs the packet data stored at the destination indicated by the address. Output time measuring unit 15
Measures the time at which the head of each packet is output from the stream multiplexer. When each packet data is output, the output control unit 14 writes the output time measured by the output time measurement unit 15 in the output queue, and sets the output flag to 1. The address, the output time, and the output flag are read and written sequentially from the top of the array forming the output queue.
When the end of the array is reached, just like in the input queue,
Return to the top of the array and repeat the above steps.

The PCR correction means 17 includes the output order determination means 1
If the packet of the address passed from 6 contains a PCR, as described above, the PCR correction value is calculated from the input time and the output time simultaneously with the address, and the PCR is corrected.

As described above, according to the present embodiment, the data of each input stream is input to one buffer memory,
By managing the contents in the input queue and the output queue, the number of buffer memories can be reduced.
Further, according to the present embodiment, the PCR is performed using the input time and the output time of each packet recorded in the buffer memory.
A correction value of the PCR can be obtained before outputting the packet.

[0025]

According to the first to fourth aspects of the present invention, with a simple configuration using one buffer memory,
Stream multiplexing and PCR correction can be realized.

In particular, according to the first aspect of the present invention, it is not necessary to provide a buffer memory for each input stream, so that the apparatus scale can be reduced.

According to the second aspect of the present invention, the input / output bus operates at a high speed and the control bus operates at a low speed, so that a high-performance multiplexer can be realized without using expensive components. .

According to the third aspect of the present invention, PCR can be corrected with high accuracy and a simple configuration.

According to the fourth aspect of the present invention, the output order can be determined with high accuracy and a simple configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a stream multiplexing device according to an embodiment of the present invention.

FIG. 2 is a memory map showing storage locations of packets, input times, and output times in a buffer memory used in the stream multiplexing device of the present embodiment.

FIG. 3 is a time chart showing a method of correcting a PCR in the stream multiplexing device of the present embodiment.

FIG. 4 is a system configuration diagram of a CS broadcast including a conventional stream multiplexing device.

[Explanation of symbols]

 10A to 10N Input unit 11 Output unit 12 Input time measurement unit 13 Input control unit 14 Output control unit 15 Output time measurement unit 16 Output order determination unit 17 PCR correction unit 18 Buffer memory 19 Input / output bus 20 Control bus

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 7/08 H04N 7/08 Z 9A001 7/081 7/13 Z 7/24 F term (reference) 5C059 KK08 KK34 MA00 RB02 RB06 RB10 RB16 RC04 RC08 RE04 SS02 UA02 UA05 UA38 5C063 AA01 AB03 AB07 AC01 AC05 CA11 DA07 DA13 5K028 AA07 CC02 DD01 DD02 EE03 EE05 EE07 FF11 KK01 KK12 KK24 NN34 NN34 MM07 JA01 KA02 KA19 KA21 LD07 LE06 5K047 AA16 BB05 CC02 DD01 DD02 GG45 HH01 HH11 JJ06 LL06 MM12 MM24 9A001 BB03 BB04 CC02 HH34 KK60

Claims (4)

[Claims] 1. A stream multiplexer for multiplexing and outputting a plurality of input streams, comprising: input time measuring means for measuring an input time of each input packet in each input stream; Output time measuring means for measuring an output time of an output packet; an input queue for temporarily holding the input packet and its input time; and a buffer memory having an output queue for temporarily holding the output packet address and its output time; Output order determining means for determining the output order of each packet stored in the input queue of the buffer memory; and a case where the output order determining means includes a PCR (program clock reference) in the packet whose output order is determined by the output order determining means. And PCR correction means for rewriting the PCR. Stream multiplexing apparatus according to symptoms. 2. The buffer memory is connected to the input time measuring means and the output time measuring means via an input / output bus, and connected to the output order determining means and the PCR correcting means via a control bus, 2. The stream multiplexing apparatus according to claim 1, wherein the writing and reading of each packet to and from the buffer memory and the writing of the input time and the output time are performed using the input / output bus. 3. The PCR correction means rewrites the PCR using an input time of a specific packet stored in the buffer memory and an output time of a packet already output earlier than the specific packet. The stream multiplexing device according to claim 1, wherein: 4. The output order determining means determines an output order using an input time of each packet stored in the buffer memory and an output time of each packet already output. The stream multiplexing device according to claim 1.