JP4565995B2 - Real-time data transmission device - Google Patents

Description

The present invention relates to a payload portion of a PES packet of digital broadcasting, data group data of analog broadcasting VBI data broadcasting (conforms to the encoded transmission system character broadcasting of the electric engineering trial report in March 1985), ASC data broadcasting (same as above) Similar transmissions that may be put into practical use in the future or whose transmission timing and transmission speed are determined based on external conditions such as available bandwidth, data signal field period, ASC frame period, etc. The present invention relates to a real-time data transmission apparatus that transparently transmits random arrival data (hereinafter referred to as real-time data) of indefinite length and discontinuity on a road.
Here, “transparently” means that the irregular interrupted portion present in the transmission data is transmitted in the form as it is.

As an example of such a transmission path, TS (Transport Stream) can efficiently multiplex various signals such as video and audio without depending on the type, so a wide range of media such as CS, BS, CATV, terrestrial waves, etc. It is used in.
Since data can be transmitted serially at the same time, it has been used for real-time information transmission, such as stock price information, weather information, and traffic information, which change from time to time by taking advantage of the simultaneous and broadcast data broadcasting.

As shown in FIG. 5, the TS is a continuous stream of 188-byte fixed-length packets called TS packets, and the TS packet is composed of a fixed-length header and a payload portion.
A signal that is an element constituting content such as video, audio, and data is called an ES (elementary stream), and ES that is divided into variable-length blocks and added with header information is called a P (packetized) ES.
The PES is divided and stored in the payload portion of one or more TS packets.
The header part of the TS packet has an identification code area called PID, and the original PES can be restored by connecting the data of the payload part of the TS packet having the same PID value on the receiving side.

When transmitting real-time data transparently using a TS packet as a transmission path, the transmission data is divided into fixed-length blocks of a fixed length in the order of arrival, header information is added to the fixed-length blocks, and a PES is generated. Is stored in the payload portion of the TS packet and transmitted.
That is, indefinite-length real-time data is divided into n fixed-length blocks to generate n PESs, which are transmitted on n TS packets corresponding one-to-one.

FIG. 6 shows a time chart in the case of transmitting real-time data using TS packets as transmission paths.
As an example of real-time data, it is easy to understand the case where a DGPS (differential GPS) correction signal is transmitted, and this will be described as an example.
The figure shows a case where the bit rate of the TS packet serving as the transmission path is slightly higher than the bit rate of the real-time data, and both bit streams are displayed side by side on the same time axis.
The DGPS correction signal is a stream in which transmission data A, B,..., Randomly arriving at random, intermittently continuous without being synchronized with the transmission cycle of the TS packets P1, P2,. Are indefinite length non-signal periods G1, G2,.
In the figure, the transmission data A, B... Are shown to be stored directly in the payload portion of the TS packet, but in reality, they are once stored in the payload portion of the PES and then stored in the payload portion of the TS packet for transmission. To do.

In the figure, when the non-signal periods G1, G2,... Are long, if the transmission of the previous transmission data A, B, .... is delayed until the next transmission data B, C ... arrives, the DGPS correction signal does not function effectively. It is necessary to transmit the next transmission data B, C... After a certain time-out period (usually in time with the next transmission timing of the TS packet) counting from the end time of the previous transmission data A, B.
In the figure, when the length of the TS packet is p, the length of the transmission data A is a1, the length of the transmission data B is b1 + b2, the length of the transmission data C is c1 + c2 + c3, and the length of the transmission data D is d1 + d2 + d3 + d4, 1) Transmission data A is stored in the TS packet P3 (a1), and the remaining space of the TS packet P3 has a length p-a1.
{Circle around (2)} Transmission data B is stored in two TS packets P5 (b1) and P6 (b2), and free spaces of lengths p-b1 and p-b2 are created in the remaining spaces of TS packets P5 and P6, respectively.
(3) Transmission data C is stored in three TS packets P9 (c1), P10 (c2 = p) and P11 (c3), and the lengths p-c1 and p-c3 are stored in the remaining spaces of the TS packets P9 and P11, respectively. Can be free.
(4) Transmission data D is stored in four TS packets P13 (d1), P14 (d2 = p), P15 (d3 = p), and P16 (d4), and the lengths are stored in the remaining spaces of TS packets P13 and P16, respectively. p-d1 and p-d4 are vacant.

Since the TS packet is a fixed-length block, it is necessary to supplement dummy data such as NULL (0) in a free area formed in the remaining space and transmit it.
On the other hand, the side receiving the TS packet does not know unless there is an explicit indication that the remaining space contains dummy data, so this is received as valid data, and as a result, numerical data may be processed incorrectly, or in some cases A code error may occur and the data processing program may go down.
This is a case where the data processing program on the receiving side is intended for operation on a continuous transmission line, and the invalid part is designed on the assumption that there is no signal, not dummy data.

  The problem to be solved is that when transmitting indefinite-length real-time data in a packet, if the empty data area formed in the remaining space of the packet is supplemented with dummy data such as NULL and sent out, the numerical data in the receiving side data processing program is transmitted. Processing errors and code errors may occur, and the present invention makes it possible for a data processing program on the receiving side to identify valid data so that numerical data processing errors and code errors do not occur. It was made for the purpose.

Therefore, the present invention uses a transmission path composed of n fixed-length transmission blocks having a fixed bandwidth that is intermittently opened at a transmission timing of a fixed period, and generates irregular transmissions that are generated in real time without being synchronized with the transmission timing. In the case of transmitting indefinite-length real-time data including intermittence into n fixed-length blocks and transmitting them transparently, on the transmission side, the storage means for storing the real-time data in the block buffer byte by byte in the order of arrival; Each time the transmission timing of a certain period comes, an extraction means for extracting the stored real-time data from the block buffer , an adding means for adding effective data identification information according to the length of the extracted real-time data , and effective data identification information Bei and transmission means for transmitting the added real-time data carried on the fixed length transmission block The receiving side, and separating means for separating the blocks of the same ID from among the n fixed-length transmission block received, the valid data identification information of the real-time data stored in the fixed-length transmission block of discrete same ID The main feature is that it comprises extraction means for extracting only valid data by reference, and restoration means for connecting the extracted n valid data to restore the original real-time data .

  In the present invention, since the effective data identification information is added to the real time data stored in the packet on the transmission side and transmitted, and only the effective data is extracted from the packet with reference to the effective data identification information on the reception side, the received real time data is received. Dummy data such as NULL is eliminated from the data, and it is possible to prevent an accident in which the data processing program on the receiving side causes a numerical data processing error or goes down during data processing.

  Embodiments of the present invention will be described below.

FIG. 1 shows a configuration diagram of a real-time data transmission apparatus embodying the present invention.
In this embodiment, an example in which a TS packet is used as a transmission path has been described. However, as described above, various transmission paths are possible, and the transmission path of the present invention is not limited to a TS packet.
In the real-time data transmission apparatus, an encoder 1, a MUX (multiplexer) 2 and a transmitter 3 are arranged on the transmission side, and a tuner 4 and a decoder 5 are arranged on the reception side.
The encoder 1 on the transmission side inputs real-time data of indefinite length, divides it into fixed-length blocks in the order of arrival, adds header information to the fixed-length block, generates a PES, and stores the PES in the payload portion of the TS packet. Send to MUX2.
MUX2 inputs TS packets and time-division multiplexes them into one TS.
The transmitter 3 receives TS, converts it into a broadcast signal, and transmits it via the antenna T1.

The tuner 4 on the receiving side selects a broadcast signal received by the antenna T2 and outputs a TS.
The decoder 5 receives the TS, separates the TS packet, extracts the PES from the payload portion of the TS packet, extracts only valid data from the PES, and restores the original real-time data.

FIG. 2 shows a data format of a TS packet used as a transmission path.
The TS packet is a 188-byte fixed-length packet, which is composed of a 4-byte header part and a 184-byte payload part, and stores the PES in the payload part.
The PES is a 184-byte fixed-length packet, which is composed of a 9-byte header part and a 175-byte payload part, and stores real-time data in the payload part.
The real-time data is stored in the payload portion of the PES with a fixed-length block of 174 bytes, with an effective data length of, for example, 1 byte added to the head.
When the effective data length of the real-time data is n (n <174), n is set to the effective data length of the TS packet, and the remaining empty portion of the TS packet is filled with dummy data of length (174-n). .
The above TS and PES are ITU-T recommendation / international standard H.264. According to the definition of MPEG-2 Systems specified by 222.0 and ISO / IEC13818-1.

FIG. 3 shows a block diagram of the encoder.
The encoder of the present embodiment is an example, and the encoder structure itself is not limited thereby.
The encoder 1 includes bit decoding 11, byte decoding 12, and packetization processing 13.
The bit decoder 11 samples and encodes the input real-time data in units of bits, and transfers the bits to the bit buffer B1 bit by bit.
The byte decoder 12 inputs a bit code from the bit buffer B1, assembles 1 byte, and transfers it to the byte buffer B2 byte by byte.
When the byte buffer B2 receives 1 byte, it stores it in the block buffer B3 byte by byte.
The packetizing process 13 takes out real-time data from the block buffer B3 in accordance with the transmission timing of the TS packet, adds a header to the real-time data, generates a PES, stores the PES in the payload portion, and outputs the TS packet.
At this time, for example, an effective data length of 1 byte is set as effective data identification information at the head of the PES payload.
Further, the next block buffer B3 is prepared and the next block is received.

FIG. 4 shows a block diagram of the decoder.
The decoder of the present embodiment is an example and does not limit the structure of the decoder.
The decoder 5 includes a separation / extraction process 51, byte decomposition 52, and bit transmission 53.
The separation extraction process 51 separates TS packets having the same PID value by inputting TS, extracts only valid data from the PES payload by referring to the valid data length of the PES stored in the TS payload, and extracts the valid The data is connected and restored to the original real-time data, which is transferred to the block buffer B3.
The byte decomposition 52 inputs real-time data restored from the block buffer B3, adds a transmission control code, decomposes it into 1 byte, and stores it in the byte buffer B2.
The bit transmission 53 receives 1 byte from the byte buffer B2 and breaks it into bits, transfers it to the bit buffer B1, and transmits a bit code.

It is a block diagram of the real-time data transmission apparatus which implemented this invention. This is the data format of the TS packet. It is a block diagram of an encoder. It is a block diagram of a decoder. It is a data related figure of TS / TS packet / PES. It is a time chart in the case of transmitting real-time data.

1 Encoder 11 Bit decoding 12 Byte decoding 13 Packetization process 2 MUX
3 Transmitter 4 Tuner 5 Decoder 51 Separation and Extraction Processing 52 Byte Decomposition 53 Bit Transmission T Antenna

Claims (1)

An indefinite length including irregular interruptions generated in real time without synchronizing with the transmission timing using a transmission path consisting of n fixed-length transmission blocks of a fixed bandwidth that are intermittently opened at a transmission timing of a fixed period Real-time data is divided into n fixed-length blocks and transmitted transparently,
On the sending side,
Storage means for storing the real-time data in the block buffer byte by byte in the order of arrival;
Taking out the real-time data stored so far from the block buffer every time the transmission timing of the predetermined period comes;
An adding means for adding valid data identification information according to the length of the extracted real-time data ;
Transmission means for transmitting real-time data with valid data identification information on the fixed-length transmission block ; and
With
On the receiving side,
Separating means for separating blocks having the same ID from n received fixed-length transmission blocks;
An extraction means for extracting only valid data with reference to valid data identification information of real-time data stored in the separated fixed-length transmission block of the same ID ;
A restoration means for connecting the extracted n pieces of valid data to restore the original real-time data ;
A real-time data transmission apparatus comprising:

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