JPH11341056A - Multiplexing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiplexing device having small hardware scale and flexible configuration. SOLUTION: A control part 12 generates a transport stream(TS) packet by adding a transport packet header to a PES packet under the control of its software and stores the generated TS packet in a stream generation/ multiplex intermediate buffer 13. The control part 12 reads out a video TS packet and an audio TS packet generated and stored by the buffer 13 and a PCR(program time base reference value) packet stored in its inside to an output buffer 16 based on the satisfied volume of a virtual buffer to control them. When a difference between a bit clock generated from a timing generator 14 and an output transmission line clock inputted from the external exceeds a fixed value, a null packet request generator 15 outputs a request for sending a null packet from the control part 12 to the output buffer 16 to the control part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a multiplexing device,
In particular, the present invention relates to a multiplexer for multiplexing a plurality of elementary streams and transport streams.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional multiplexer. In the figure, an input stream such as a video elementary stream obtained by compression-encoding a video signal by the MPEG2 encoding method and an audio elementary stream obtained by compression-encoding an audio signal by the MPEG2 encoding method are as follows: After being supplied to the multiplexing unit 1, each elementary stream is divided so as to be a multiple of the unit time, and a header is added and packetized, each is further divided, and the packet header is divided. Is added and then time-division multiplexed to form a transport stream (TS).

[0003] The TS packets extracted from the multiplexing unit 1 are output by a smoothing unit 2 at a predetermined rate synchronized with an input clock, supplied to an output buffer 3, and temporarily stored.
On the other hand, if there is a TS packet in the output buffer 3 at the output transmission line clock, the output control unit 4 reads out the TS packet from the output buffer 3 and supplies it to the terminal 5a of the switch circuit 5. The null packet is read out from the null packet transmitting unit 6 and supplied to the terminal 5b of the switch circuit 5.

A switch circuit 5 is controlled under the control of an output control unit 4.
The TS packet or the null packet that has been switched and extracted from is supplied to the header changing unit 7, where
The program time reference value (PCR) multiplexed in the S packet is appropriately changed, and is transmitted to the transmission path as an output stream.

[0005]

However, in the above-described conventional multiplexing apparatus, the relationship between the bit clock of the input stream and the bit clock of the output stream is not always synchronized, while the output stream is not synchronized. Since it is necessary to transmit data at a constant rate without any shortage, two output buffers 3 are provided in parallel, and one output buffer is operated for writing while the other output buffer is operated for reading, thereby continuously controlling TS. The packet is taken out. For this reason, the conventional multiplexing apparatus has a problem that the scale of the hardware is large, and it is difficult to cope with various specifications of the configuration of the transmission path and the receiving apparatus and the flexibility is poor.

Further, in the conventional multiplexing apparatus, since the insertion of null packets is multiplexed into the stream from the output buffer 3, the position of the null packet is determined when multiplexing a plurality of types of input streams. MTU of ATM (asynchronous transfer mode) that cannot reflect the multiplexing and transmits a plurality of TS packets in a single transmission path and transmission mode
Not available for mode.

[0007] The present invention has been made in view of the above points,
It is an object of the present invention to provide a multiplexer having a small hardware scale and a flexible configuration.

Another object of the present invention is to provide a multiplexer which can be used in the MTU mode of ATM (Asynchronous Transfer Mode).

[0009]

In order to achieve the above object, the present invention provides a method for compressing and encoding one or more information signals by a predetermined encoding method from one or more elementary streams. An input buffer for temporarily storing an input stream, and a control for generating transport stream packets by software from the input stream stored by the input buffer, managing the stream generation amount, and multiplexing and outputting the transport stream packets. Means, a timing generator for generating a clock synchronized with the bit clock of the input stream, and supplying a null packet request to the control means when a difference between the bit clock and the clock of the output stream becomes a certain value or more. In the transport stream packet generated by the control means. A null packet request generator for inserting a new packet, and a stream generated and multiplexed and taken out by the above-mentioned control means, temporarily stored, and then continuously output as an output stream in synchronization with a bit clock of the output stream. And a read buffer.

According to the present invention, a transport stream packet is generated by software based on an input stream, the amount of stream generation is managed, and the transport stream packet is multiplexed and output. When the difference between the bit clock and the clock exceeds a certain value, a null packet request is generated and a null packet is transmitted, so that the difference between the bit clock of the input stream and the bit clock of the output stream is compensated. , A continuous stream in which null packets are inserted into transport stream packets.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a multiplexing apparatus according to the present invention. In FIG. 1, a multiplexing unit 10 includes an input interface and an input buffer 11.
, A control unit 12 and a stream generation / multiplex intermediate buffer 13. The input interface and the input buffer 11 are constituted by a FIFO (first-in first-out) memory. The input interface and the input buffer 11 transfer the input stream to the main buffer, the stream generation / multiplex intermediate buffer 13 for a short period of time. It is for accumulation.

The control unit 12 has a high-speed central processing unit (CP)
U), a dynamic random access memory (DRAM) managed by the CPU, and a read-only memory (ROM) in which a program is stored. ) Is generated and multiplexed, the generation amount of the multiplexed stream to be generated is obtained by calculation, the bit clock frequency thereof is set in the timing generator 14, and a null packet request is output from the null packet request generator 15. Packets are generated by software.

Stream generation / multiplex intermediate buffer 13
Is a part of a RAM attached to the CPU in the control unit 12 and serves as an intermediate buffer for generating a transport stream (TS) from an elementary stream (ES) and for multiplexing the generated TS. Used as a buffer for

The timing generator 14 has a configuration in which the frequency of the output clock can be varied by setting from the control unit 12, and accurately counts the timing of the generated stream. Timing generator 14
Can be generally configured by a phase locked loop (PLL) circuit, and the control unit 12 sets the frequency division ratio of a variable frequency divider in a feedback loop that supplies a control voltage to a voltage controlled oscillator in the PLL circuit. Then, an input signal clock is supplied as an input signal to the phase comparator in the PLL circuit, and a bit clock synchronized in phase with the input signal clock is generated.

The null packet request generator 15 counts the difference between the bit clock of the output stream and the clock from the timing generator 14, which is the bit clock of the internally generated stream, and determines the number of bits of the TS packet as 1504. Issue a null packet request when counting clocks.

The output buffer 16 is composed of a FIFO memory and is used for converting the speed of the output stage.
The header changing unit 17 appropriately changes the program time reference value (PCR) multiplexed in the TS packet. In this embodiment, by separately providing clock synchronization,
A plurality of TS packets can be sent to the output unit at one time, and the configuration is suitable for software processing.

Next, the operation of this embodiment will be described. A video elementary stream obtained by encoding a video signal by the MPEG2 encoding method and an audio signal
An input stream such as an audio elementary stream obtained by encoding according to the PEG2 encoding method is supplied to the input interface and the input buffer 11 in a burst form and temporarily stored. This is because it is difficult to perform these processes at the moment when a stream is input for input processing, output processing, or packetization processing by software processing.

Input Interface and Input Buffer 11
The video ES and the audio ES, which are the input streams stored in the first and second streams, are divided such that the header is detected and the size of the stream is a multiple of a unit time (access unit).
3 and stored.

Stream generation / multiplex intermediate buffer 13
Is a video ES and an audio ES, which are inputted with the PES header generated by the control unit 12 and divided.
To generate a PES packet, and further, the PES packet
A TS packet is generated by dividing the header and adding a transport packet header generated under the control of software of the control unit 12, and the generated video TS packet is stored in a video buffer in the stream generation / multiplex intermediate buffer 13. The stored audio TS packets are stored in an audio buffer in the stream generation / multiplex intermediate buffer 13.

On the other hand, apart from the generation of the video TS packet and the audio TS packet, in MPEG2, there is a PCR packet indicating a program time reference value, which enables the receiving device to reproduce the video clock. The control unit 12 generates a packet and accumulates the packet in an internal PCR buffer. Along with the generation of the TS packet, flag information such as what is included in the packet is also generated by the control unit 12 to generate a stream.
The data is input to the multiplex intermediate buffer 13.

Next, the control unit 12 stores the video TS packets and the audio TS packets generated and stored in the stream generation / multiplex intermediate buffer 13 and the PCR packets held therein in a virtual manner assuming a reception buffer. Based on the buffer sufficiency (occupancy), read control to the output buffer 16 is performed according to the flowchart of FIG. The CPU in the control unit 12 has the type of the input stream and the frequency of the bit clock thereof as known information, obtains the multiplexed frequency by calculation, and calculates the bit clock frequency obtained by the calculation by the timing generator 14. Set to.

Next, read control by the control unit 12 in accordance with the virtual buffer fullness will be described in detail with reference to the flowchart of FIG. First, the control unit 12 obtains an audio TS rate from the audio ES rate obtained from the input interface and the input buffer 11,
The video TS rate is determined from the rate, the appropriate PCR packet rate is determined from the total TS rate and the number of MTU units, and the overall TS rate and video, audio,
From the ratio of each TS rate of the PCR, the virtual buffer fullness per 1 TS packet transmission time is obtained (step 2).
1). Here, the virtual buffer is video, audio, P
There is one for each TS packet in the CR.

Subsequently, the control unit 12 controls the output buffer 16
To determine whether a TS packet can be transmitted to the
2) After waiting for transmission, it is determined whether or not the PCR virtual buffer sufficiency is equal to or greater than 1 TS packet (step 23).
The PCR buffer in 2 is transmitted with one TS packet for one TS packet to the output buffer 16 through the stream generation / multiplex intermediate buffer 13 and the PCR virtual buffer filling amount is reduced by one TS packet (step 24).

On the other hand, if it is determined in step 23 that the PCR virtual buffer is not more than one TS packet,
The control unit 12 determines whether the audio virtual buffer fullness is equal to or more than 1 TS packet (step 25).
It is determined whether there is more than the number of TS packets (step 26). If the amount of video virtual buffer filling is more than one TS packet, the video weighting number PRIv and the audio weighting number PRIa are calculated (step 27). Where PRI
It is calculated by v = _evbuf / _devuf , PRIa = _eabuf / _devuf . Here, _evbuf is the video virtual buffer _fullness , _devbuf is the video virtual buffer _fullness per TS packet transmission time, e _abuf is the audio virtual buffer _fullness , and de _abuf is the audio virtual buffer fullness per TS packet transmission time. is there.

Subsequently, the video weighting number PRI v is oh
Judge whether it is greater than the Dio weighting number PRIa
(Step 28) If large, stream generation / multiplexing is in progress
From the video buffer in the inter-buffer 13 to the output buffer 1
Send video TS packets for 1 TS packet to 6
Together with the video virtual buffer capacity by 1 TS packet
Rashi (step 29), if small, stream generation / many
Output buffer from the audio buffer in the
Audio TS packet to the buffer 16
And the audio virtual buffer is full
It is reduced by TS packets (step 30).

On the other hand, if it is determined in step 25 that the audio virtual buffer is less than one TS packet, it is determined whether the video virtual buffer is less than one TS packet (step 31). If the sufficiency is equal to or greater than 1 TS packet, the video buffer transmits 1 TS packet and the video TS packet from the video buffer to the output buffer 16 and reduces the sufficiency of the video virtual buffer by 1 TS packet (step 2).
9) If both the audio virtual buffer fullness and the video virtual buffer fullness are less than 1 TS packet, T
In order to maintain the continuity of the S packet, a null packet is transmitted to the output buffer 16 through the stream generation / multiplex intermediate buffer 13 (step 32).

As described above, the control unit 12 sends one of the PCR packet, the video TS packet, the audio TS packet, and the null packet to the output buffer 16 for one TS packet based on the calculated virtual buffer filling amount. Then, the PCR virtual buffer sufficiency per 1 TS packet transmission time is added to the PCR virtual buffer sufficiency (step 33). Subsequently, the control unit 12 checks whether a null packet request has been received from the null packet request generator 15 (step 34).

Here, the null packet request generator 15
The difference between the bit clock of the internally generated stream input from the timing generator 14 and the output transmission line clock (bit clock of the output stream) input from the outside is counted, and the difference is the number of bits of the TS packet. When the value of a certain 1504 clocks is reached, a request for a null packet is supplied to the control unit 12. If the control unit 12 determines in step 34 that a null packet request has been received from the null packet request generator 15, the control unit 12 returns to the process in step 22. If it determines that a null packet request has not been received, the audio virtual buffer After adding the audio virtual buffer filling amount per 1 TS packet transmission time to the filling amount, and adding the video virtual buffer filling amount per 1 TS packet transmitting time to the video virtual buffer filling amount (step 35), Return.

FIG. 3 shows an example of a temporal change of the virtual buffer filling amount. In the figure, the solid line I represents the video virtual buffer fullness, the dotted line II represents the audio virtual buffer fullness,
The dashed-dotted line III indicates the amount of the filled PCR virtual buffer. In addition, video packets (diamonds) and audio packets (+
), A null packet (open square mark) or a PCR packet (cross mark) is sent to the output buffer 16.

Referring back to FIG. 1, the output buffer 16 includes an output data buffer for storing TS packets generated by software and input from the multiplexing unit 10, and a flag that can be changed in byte units. And an output flag buffer that is input from the multiplexing unit 10 and accumulates. The output data buffer has several TS packets written therein at one time, and the TS packets are continuously written in synchronization with the output transmission line clock. The data is read and supplied to the header changing unit 17. The header changing unit 17 appropriately changes the value of the PCR based on the flag from the flag buffer.

The header changing unit 17 serially outputs time-division multiplexed video packets, audio packets, null packets, and PCR packets as an output stream to, for example, an ATM line modulator or a satellite line modulator. The flags from the flag buffer are also output in parallel with the output stream. With this flag,
The device to which the output stream is input can reprocess the input stream without analyzing the input stream.

As described above, in this embodiment, a TS packet is generated by software and the output buffer 1
6, the program stream multiplexing method can be dealt with by changing the software as well as changing the specification of TS packets and adding a flag.

In this embodiment, a TS packet generated by software is synchronized with an input signal clock (video clock) in order to transmit a continuous packet to a transmission apparatus which is not synchronized with the video frame frequency. Next, the null packet request generator 15 outputs a bit clock (synchronized with the video clock) of the internally generated stream input from the timing generator 14 and an output transmission line clock (output stream) input from the outside. By counting the difference from the bit clock, the request for the null packet is supplied to the control unit 12 when the difference reaches the value of the TS packet, and the null packet is transmitted.
Since the difference between the bit clock of the input stream and the bit clock of the output stream is compensated, the generated TS packet can be output in synchronization with the transmission line clock. Thus, this embodiment can be used for the MTU mode of ATM.

The present invention is not limited to the above embodiment, and the input stream may be a single elementary stream.

[0035]

As described above, according to the present invention,
A transport stream packet (TS packet) is generated by software based on the input stream,
In addition, since the stream generation amount is managed and the TS packets are multiplexed and output, not only can the specifications of the TS packets be changed or flags added, but also the program stream multiplexing method can be flexibly handled by changing the software, In addition, the hardware can be configured in a simple and small-scale configuration as compared with the related art.

According to the present invention, a TS packet generated by software is synchronized with an input signal clock, and when a difference between a bit clock and a clock of an output stream becomes equal to or greater than a predetermined value, a null packet request is output. Is generated, a null packet is sent to the output buffer to compensate for the difference between the bit clock of the input stream and the bit clock of the output stream. Therefore, the generated TS packet is synchronized with the bit clock of the output stream. Thus, a continuous packet can be transmitted to a transmission system device that is not synchronized with the video frame frequency, and can be used in the MTU mode of ATM.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a TS packet transmission operation by a control unit in FIG. 1;

FIG. 3 is a diagram showing an example of a temporal change of a virtual buffer filling amount by software control of a control unit in FIG. 1;

FIG. 4 is a block diagram of an example of the related art.

[Explanation of symbols]

 Reference Signs List 10 multiplexing unit 11 input interface and input buffer 12 control unit 13 stream generation / multiplex intermediate buffer 14 timing generator 15 null packet request generator 16 output buffer 17 header changer

Claims (3)

[Claims] An input buffer for temporarily storing an input stream composed of one or more elementary streams obtained by compression-encoding one or more information signals by a predetermined encoding method, and Control means for generating a transport stream packet from the accumulated input stream by software, and managing the stream generation amount to multiplex and output the transport stream packet; and a clock synchronized with a bit clock of the input stream. And a timing generator that generates a null packet request when the difference between the bit clock of the output stream and the clock becomes equal to or greater than a predetermined value, and supplies a null packet request to the control unit to generate the null packet request. Insert the null packet in the port stream packet A null packet request generator to be input, and a stream generated by the control means and multiplexed and taken out is temporarily stored, and then read out continuously as the output stream in synchronization with a bit clock of the output stream. A multiplexer comprising an output buffer. 2. The control means according to claim 1, wherein said control means divides an input stream from said input buffer under software control, and adds a packet header to each of said divided streams to produce said transport stream. A stream packet is generated and stored in the intermediate buffer, a stream in which the transport stream packet is multiplexed is read out from the intermediate buffer by managing the stream generation amount, and the stream is supplied to the output buffer. 2. The multiplexing apparatus according to claim 1, further comprising a control unit that, when a null packet request is issued from the generator, inserts the null packet generated by software into the multiplexed stream output from the intermediate buffer. Device. 3. The input stream includes a video elementary stream and an audio elementary stream. The control unit generates video TS packets and audio TS packets by software based on the input streams, and generates the null packets. And a PCR packet of a time reference value are generated by software, and for each of the generated video TS packet, audio TS packet, and PCR packet, the fullness of a virtual buffer for virtually storing the packet is 1T.
It monitors whether there are S packets, and sends the output buffer through the intermediate buffer for packets having a virtual buffer sufficiency of 1 TS packet. If none of the virtual buffers are satisfiable for 1 TS packet, the null packet is sent. 3. The multiplexing device according to claim 2, wherein the signal is sent to said output buffer through an intermediate buffer.