KR20010075849A - Synchronous video terminal using isdn video codec and method for controlling data stream using the same - Google Patents

Abstract

PURPOSE: A synchronous video terminal apparatus using a video coder for an ISDN(Integrated Services Digital Network) and data flowing control method thereof is provided to prevent the loss and delay of a transmitting and receiving compression data by generating a network synchronous clock signal from a synchronous signal of an advanced mobile communication(IMT-2000) network to provide the generated network synchronous clock signal continuously and adjusting a data quantity of a buffer according to a transmission bit rate. CONSTITUTION: An ISDN video coder(7) supports a multiplexing and demultiplexing to a compressed an audio/video data according to a standard and performs a compression and decompression to the audio/video data. A transmitting FIFO(8) stores the audio/video compression data outputted from the ISDN video coder(7). A receiving FIFO(9) stores a received audio/video compression data and provides the stored audio/video compression data to the ISDN video coder(7) when being requested by the ISDN video coder(7). A synchronous signal generating circuit(11) generates a network synchronous signal of the ISDN video coder(7) using a transmitting and receiving frame synchronous signal and a reference clock. A CPU(10) provides a transmitting and receiving timing interrupt signal using the transmitting and receiving frame synchronous signal, reads data from the transmitting FIFO(8) when generating the transmitting and receiving timing interrupt to compose the read data as a wireless transmission frame and transmit the wireless transmission frame, and decomposes a received wireless receiving frame to store a decomposed data.

Description

SYNCHRONOUS VIDEO TERMINAL USING ISDN VIDEO CODEC AND METHOD FOR CONTROLLING DATA STREAM USING THE SAME}

The present invention relates to a synchronous video terminal device using a video encoder for an Integrated Services Digital Network (ISDN), a data flow control method thereof, and a computer-readable recording medium recording a program for realizing the method. In particular, a synchronous video terminal device for transmitting video and audio information in a next generation mobile communication (IMT-2000) network, an ISDN video encoder, a data flow control method thereof, and a computer for recording the program for realizing the method. To a recording medium.

Next-generation mobile communication (IMT-2000) is a system that can provide all possible mobile communication services by integrating various mobile communication networks and services formed to provide various types of existing services. In addition, various types of wireless access and a large capacity of subscribers enable high-speed multimedia communication such as voice, video, and data. In particular, mobile video telephony service is expected to be one of the most widely used services in the next generation mobile communication (IMT-2000) market, and mobile video telephony for next generation mobile communication (IMT-2000) service is currently focused on developed countries. I am developing a test bed to implement a service.

A mobile terminal for providing a mobile video telephone service requires a low power and high performance video encoder. In particular, a design and implementation of a video encoder for providing a video service in a next generation mobile communication (IMT-2000) service and a mobile wireless environment are provided. This requires high speed algorithm processing technology, data compression technology, high speed wireless transmission technology, and semiconductor chip design technology.

Video encoders for providing video telephony services in wired networks such as public line telephone networks (PSTN) and integrated telecommunication networks (ISDN) have been developed and commercial products are being applied. In Korea, ISDN provides video telephony or video conferencing system to provide data rates ranging from 64 kilobit per sec (kbps) to 384 kbps.Wireless communications such as next-generation mobile telecommunications (IMT-2000) There is a problem that the image encoder in the environment has not yet been implemented.

The present invention has been made to solve the problems described above, and generates a network synchronization clock signal required for an ISDN video encoder from a synchronization signal such as a next generation mobile communication (IMT-2000) network and continuously. And a video flow control method using a video encoder for an integrated information communication network, and a method for controlling the data flow thereof, which prevents loss and delay of transmission / receiving voice / video compressed data by adjusting the amount of data in a buffer according to a transmission bit rate. An object of the present invention is to provide a computer-readable recording medium having recorded thereon a program for realizing this.

1 is a block diagram of an embodiment of a synchronous video terminal device using a video encoder for an integrated information communication network according to the present invention.

Figure 2 is a detailed configuration diagram of an embodiment of a synchronization signal generation circuit according to the present invention.

3 is a flowchart illustrating a data flow control method in a synchronous video terminal device using a video encoder for an integrated information communication network according to the present invention.

* Explanation of symbols for the main parts of the drawings

1: handset 2: camera

3: liquid crystal display device 4: audio codec

5: NTSC decoder 6: NTSC encoder

7: Video encoder for ISDN 8: Transmit FIFO

9: receive FIFO 10: central processing unit

11: sync signal generator 12: 20 MHz clock generator

13: terminal modem 14: IF / RF processor and antenna

An apparatus of the present invention for achieving the above object is a synchronous video terminal device using a video encoder for an Integrated Services Digital Network (ISDN), the multiplexing and de-decoding according to a given standard for compressed audio / video data Image encoding means for an integrated information communication network (ISDN) for supporting multiplexing and for performing compression and reconstruction on audio / video data; Transmission data storage means for storing audio / video compressed data output by the video encoding means for the ISDN; Received data storage means for storing the received audio / video compressed data and providing the same upon request of the video encoding means for the ISDN; Synchronizing signal generating means for generating a network synchronizing signal of the video encoding means for the ISDN by using a transmission / reception frame synchronizing signal and a reference clock; And a transmission / reception timing interrupt signal using the transmission / reception frame synchronization signal, reads data from the transmission data storage means when the transmission / reception timing interrupt signal is generated, configures the transmission data into a wireless transmission frame, and transmits the received wireless reception frame. And a central processing unit for decomposing and storing the received data storage unit.

In addition, the method of the present invention is a data flow control method applied to a synchronous video terminal apparatus using a video encoder for an integrated information communication network (ISDN), the first step of setting the amount of data transmission at a reference time according to the selected transmission bit rate ; A second step of obtaining a threshold setting value in consideration of the storage capacity of the transmission data storing means; When the transmission / reception timing interrupt occurs, the amount of data stored in the transmission data storage means is compared with the threshold setting value, and if it is less than the threshold setting value, it waits until the next transmission / reception timing interrupt. A third step of processing; And a fourth step of reading a received frame upon generation of a transmission / reception timing interrupt and storing the received frame in the received data storing means according to the set data transmission amount.

The present invention also provides a synchronous video terminal device having a processor, comprising: a first function of setting a data transmission amount at a reference time according to a selected transmission bit rate; A second function of obtaining a threshold setting value in consideration of the storage capacity of the transmission data storing means; When the transmission / reception timing interrupt occurs, the amount of data stored in the transmission data storage means is compared with the threshold setting value, and if it is less than the threshold setting value, it waits until the next transmission / reception timing interrupt. A third function to process; And a computer readable recording medium having recorded thereon a program for realizing a fourth function of reading a received frame upon generation of a transmit / receive timing interrupt and storing the received frame in a received data storage means according to the set data transfer amount.

The next generation mobile communication (IMT-2000) system, unlike the existing cellular network or personal communication system (PCS), is a low speed data communication network centered on voice service, up to 2Mbps within a certain service area. To enable high-speed multimedia services. Accordingly, the mobile video telephony service can provide a limited service in a lower transmission band than a conventional video compression efficiency in a high transmission band such as next generation mobile communication (IMT-2000).

For existing ISDN 64kbps in the nature of the transmission path, and to ensure the transfer rate of up to 384kbps, particularly in the case of video encoder group because it is commercially available when applying it to the IMT-2000 terminal the bit error rate is 10 ^-6 or less in a wireless environment up to 384kbps A high-definition mobile video telephone service can be realized at a transmission rate of.

In addition, when the ISDN video encoder is applied to a mobile terminal, there is an advantage that a separate data protocol does not need to be changed for a video call service with an existing ISDN wired subscriber.

The ISDN video coder is designed to comply with the Telecommunication part of International Telecommunication Union (ITU-T) Recommendation "H.320" for the purpose of providing video services over wired ISDN networks. Therefore, I / O data transmission / reception of the ISDN video encoder can be continuously provided with a network synchronization signal (8KHz) from the transmission network. If a network synchronization signal is not provided to the video encoder, call establishment and service data loss frequently occur, end-to-end quality of service, or disconnection of call.

In addition, when the video terminal is configured using the ISDN video encoder, the input / output data of the ISDN video encoder must be converted into a wireless transmission frame having a 20 ms interval according to the set data rate. In this case, a loss or delay of transmission / reception data may occur temporarily.

The present invention constitutes a next generation mobile communication (IMT-2000) synchronous video terminal using the existing ISDN video encoder, which is synchronized with the next generation mobile communication (IMT-2000) network required to apply the ISDN video encoder. We propose a design for a synchronization signal generation circuit that can continuously provide a synchronization signal, and efficiently control the data flow according to the data rate in order to prevent loss and delay of transmission / reception voice / video compressed data during video service.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an embodiment of a synchronous video terminal device using a video encoder for an integrated information communication network according to the present invention.

1 is a block diagram of a next generation mobile communication (IMT-2000) synchronous video telephone, including a handset (1), a camera (2), a liquid crystal display (3), an audio codec (4), and NTSC (NTSC). System Committee) decoder (5), NTSC encoder (6), video encoder (7) for ISDN, first in first out (FIFO) (8), receive FIFO (9), central processing unit (10), synchronization signal A generator circuit 11, a 20 MHz clock generator 12, a terminal modem 13, and an intermediate frequency / radio frequency (IF / RF) processor and antenna 14 are included.

The audio codec 4 receives an audio signal from the handset 1, compresses and decompresses the audio signal, and transmits and receives the compressed audio data with the video encoder 7 for ISDN. The analog video signal input from the camera 2 is converted by the NTSC decoder 5 into the YUV digital video data format of "CCIR656" standard and input to the video encoder 7 for ISDN.

Further, the reconstructed digital image data is converted into an analog image signal by the NTSC encoder 6 and displayed by the liquid crystal display device 3. The video encoder 7 for ISDN used commercial components that support the ITU-T Recommendation "H.320" standard, and compresses and decompresses digital image data according to the ITU-T Recommendation "H.261" standard. It supports multiplexing and demultiplexing of audio and video compression data according to ITU-T Recommendation "H.221".

The synchronizing signal generating circuit 11 receives a frame synchronizing signal (20 ms_sync) synchronized to the 20 milliseconds from the terminal modem 13 and generates an 8 KHz (8 KHz_sync) synchronizing signal to the ISDN video encoder 7. Is authorized.

In addition, the 20 ms_sync synchronized frame synchronization signal is applied as a 20 ms transmission / reception timing interrupt signal of the central processing unit 10. The audio / video compressed data output by the ISDN video encoder 7 is stored in the transmission FIFO 8, and is read by the central processing unit 10 every time a 20 ms transmission / reception timing interrupt signal is generated, and constitutes a wireless transmission frame. After that, it is transmitted to the terminal modem 13.

The terminal modem 13 modulates the radio transmission frame and transmits it to the IF / RF processor and antenna 14. Conversely, the data received by the IF / RF processor and the antenna 14 is demodulated by the terminal modem 13 into a radio reception frame and then transmitted to the central processing unit 10 and wirelessly received by the central processing unit 10. The frame is discarded and then stored in the receive FIFO 9. The ISDN video encoder 7 receives the compressed audio / video data stored in the reception FIFO 9 at regular intervals and performs restoration.

The ISDN video encoder is designed to comply with the ITU-T Recommendation "H.320" for the purpose of providing video services in a wired ISDN network. Therefore, the ISDN video encoder must continuously provide 8KHz of network synchronization signal.

In the present invention, a synchronization clock of 8KHz using a synchronization signal generation circuit 11 using a synchronization signal (20ms_sync) of 20ms intervals as a reference for frame transmission in a next generation mobile communication (IMT-2000) synchronous network. Generate a signal.

2 is a detailed block diagram of an embodiment of a synchronization signal generation circuit according to the present invention.

FIG. 2 is a configuration diagram of a synchronization signal generating circuit and includes a primary counter 15, a secondary counter 16, an AND logic 17, and a phase synchronization correction circuit 18.

The operation of the primary counter 15 and the secondary counter 16 of the synchronization signal generation circuit is started by a signal synchronized with 20 milliseconds (20 ms_sync). At the start of operation, the primary counter 15 counts the number of input 20 MHz (12) clocks by 1 until it reaches a predetermined count value (# 2500), and generates pulses continuously when the counter ends. Generates a kilohertz leaf (8KHz_ref) clock. At this time, the generated 8 KHz_leaf (8KHz_ref) clock is counted by incrementing by 1 in the secondary counter 16, and becomes a constant count value (# 160) and a clock signal synchronized with 20 milliseconds (20 ms_sync) is generated. When the AND logic condition 17 is satisfied, a reset signal is generated.

The reset signal initializes all count values to zero, and the primary counter 15 and the secondary counter 16 are restarted by the start signal. At this time, the clock signal of the 8 kHz_leaf (8KHz_ref) generated at the start of the pulse signal synchronized with 20 milliseconds (20ms_sync) is generated, the synchronization disturbance is formed by using the phase synchronization correction circuit 18 It is corrected to a signal synchronized to the clock signal of 8 kHz (8KHz_sync). A signal synchronized to 8 kHz (8 KHz_sync), which is a corrected synchronous clock signal, is applied to the ISDN video encoder 7 of FIG. 1 and used as a reference signal for audio / video compressed data transmission.

In the configuration of a video terminal using an ISDN video encoder as shown in FIG. 1, when data control flows of the transmission and reception FIFOs are not smoothly performed within a predetermined time, the data reception of the FIFO is temporarily accepted. The capacity may be full or empty, resulting in loss or delay of transmitted / received audio / video compressed data. In order to prevent this, the present invention controls the flow of image data as shown in FIG. 3.

3 is a flowchart illustrating a data flow control method in a synchronous video terminal device using a video encoder for an integrated information communication network according to the present invention.

FIG. 3 illustrates a flow in which the central processing unit 10 controls transmission / reception audio / video compression data according to a transmission bit rate in order to prevent loss and delay of transmission / reception audio / video compression data when providing a video service.

When the terminal is initialized, the transmission bit rate is selected (100), and the data transmission amount according to the transmission bit rate is defined (101, 102, 103, 104, 105). That is, the transmission bit rate is composed of three modes, one of which is selected, and confirming that the transmission bit rate is 384kbps (101), in the case of 384kbps, the data transfer amount is selected as 960 bytes at a reference time of 20ms (102). As a result of the check, if the transmission bit rate is not 384kbps, it is determined whether it is 128kbps (103).

As a result of the determination, the data transfer amount is selected to be 320 bytes (104) (104). As a result of the determination, if the transmission bit rate is 64 kbps if not 128kbps, the data transmission amount is selected to 160 bytes (105).

After the data transmission amount according to the transmission bit rate is defined, a threshold setting value is determined 106.

The threshold set value 107 is obtained by the following Equation 1 in consideration of the storage capacity of the FIFO.

Threshold setting = (transmission bit rate x FIFO storage) / (384 kbps x 2)

The central processing unit checks whether or not the 20 ms transmission / reception timing interrupt has occurred (107), and if it is determined that the interrupt has not occurred, repeats from step 107 of checking whether the 20 ms transmission / reception timing interrupt has occurred after waiting for a predetermined time.

As a result of the check, when an interrupt occurs, the data amount of the transmission FIFO is checked and compared with the threshold setting value (108). As a result of the comparison, if the data amount of the transmission FIFO is less than the threshold setting value, the process waits for the next 20ms transmission / reception timing interrupt and repeats from step 107 of checking whether or not the 20ms transmission / reception timing interrupt has occurred.

As a result of the comparison, when the amount of transmission / reception FIFO data is greater than or equal to the threshold setting value, the central processing unit reads the data transmission amount from the transmission FIFO by 109.

The read audio / video compressed data is transmitted to the terminal modem after being composed of transmission frames in the central processing unit (110). In addition, the central processing unit receives the frame from the modem, tears it down (111), and stores the amount of data transmission in the received FIFO (113). The process is repeated every time a 20 ms transmission / reception timing interrupt occurs until the transmission bit rate is reset or the video service is terminated.

The features of the present invention as described through the above embodiments are as follows.

The synchronous video terminal device of the present invention uses a transmission FIFO and a reception FIFO to store audio / video compressed data and control a data transmission / reception flow between an ISDN video encoder and a central processing unit, and a transmission / reception frame received from a terminal modem. A synchronization signal generating circuit for applying the synchronization signal 20ms_sync as a 20ms transmission / reception timing interrupt signal of the central processing unit, and generating a network synchronization signal 8KHz of the video encoder for ISDN using the transmission / reception frame synchronization signal 20ms_sync and the reference clock 20MHz, and for the ISDN A central processing unit controls the flow of the transmitted / received voice / video compressed data according to three transmission bit rates of 64 kbps, 128 kbps, and 384 kbps by using an image encoder.

The synchronization signal generating circuit used in the synchronous video terminal device includes a primary counter for counting a 20 MHz clock according to a start signal using a transmission / reception frame synchronization signal 20 ms_sync and a reference clock 20 MHz as inputs, and in the primary counter. A secondary counter that counts the generated 8KHz_ref signal, and the result of the AND logic of the 20ms_sync signal and the signal generated by the secondary counter are applied as reset signals, and the 8KHz_ref signal generated by the primary counter is synchronized at equal intervals. It is characterized by consisting of a phase locked correction circuit for making the clock signal 8KHz_sync.

In addition, the data flow control method in the central processing unit used in the synchronous video terminal device, if the transmission bit rate is selected from one of three of 64kbps, 128kbps, 384kbps when the terminal is initialized, the amount of data transmission is 960 at 20ms reference time, respectively The process is defined as byte, 320 byte, 160 byte, the threshold setting value is calculated as (transmission bit rate x FIFO storage) / (384kbps x 2) in consideration of the storage capacity of the transmission FIFO, and 20ms transmission and reception timing interrupt Check whether data is transmitted and compare it with the threshold setting value when the interrupt occurs, and if the data amount of the transmission FIFO is greater than or equal to the threshold setting value, read the data of the transmission FIFO by the defined data transmission amount. After configuring the transmission frame to transmit to the terminal modem, and the terminal modem Dismissing the received packet from the receiver and storing the same data transmission amount as the received FIFO, and repeating the above processes every time a 20 ms transmission / reception timing interrupt occurs until the transmission bit rate is reset or the video service is terminated. It is done.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

As described above, the present invention provides a network synchronization signal that must be continuously provided to an ISDN video encoder. A 20 ms synchronization signal with a constant interval (20 ms_sync), which is a standard for wireless frame transmission, in a synchronous network of a next generation mobile communication (IMT-2000) system. ) And a synchronization signal generation circuit to continuously provide a synchronization clock of 8KHz, thereby preventing the degradation of the quality of service or the interruption of the call during the video telephony service.

In addition, the present invention, the central processing unit of the terminal obtains the threshold setting value of the transmission FIFO according to the selected transmission bit rate, and compares the amount of the data stored in the transmission FIFO and the threshold setting value to the flow of a certain amount of transmission and reception voice / video compressed data By controlling smoothly, there is an effect of preventing data loss and delay.

Claims (5)

A synchronous video terminal device using a video encoder for an integrated services digital network (ISDN), Image encoding means for an integrated information communication network (ISDN) for supporting multiplexing and demultiplexing according to a given standard for compressed audio / video data and for performing compression and reconstruction on audio / video data; Transmission data storage means for storing audio / video compressed data output by the video encoding means for the ISDN; Received data storage means for storing the received audio / video compressed data and providing the same upon request of the video encoding means for the ISDN; Synchronizing signal generating means for generating a network synchronizing signal of the video encoding means for the ISDN by using a transmission / reception frame synchronizing signal and a reference clock; And The transmission / reception timing interrupt signal is applied using the transmission / reception frame synchronization signal, and when the transmission / reception timing interrupt signal is generated, data is read from the transmission data storage means, configured to be transmitted to a wireless transmission frame, and the received wireless reception frame is disassembled. Central processing means for storing in the received data storing means Synchronous video terminal device comprising a. The method of claim 1, The synchronization signal generating means, First counting means for counting the reference clock using the transmission / reception frame synchronization signal as a start signal; Second counting means for counting a clock of the first signal generated by the first counting means using the transmission / reception frame synchronization signal as a start signal; Logical AND operation means for performing an AND operation on the signal generated by the second counting means and the transmission / reception frame synchronization signal to transfer a reset signal to the first and second counting means; And Phase synchronizing correction means for outputting the first signal generated by the first counting means into a synchronizing clock signal with a uniform interval Synchronous video terminal device comprising a. A data flow control method applied to a synchronous video terminal device using a video encoder for an ISDN, A first step of setting a data transmission amount at a reference time according to the selected transmission bit rate; A second step of obtaining a threshold setting value in consideration of the storage capacity of the transmission data storing means; When the transmission / reception timing interrupt occurs, the amount of data stored in the transmission data storage means is compared with the threshold setting value, and if it is less than the threshold setting value, it waits until the next transmission / reception timing interrupt. A third step of processing; And A fourth step of reading a received frame upon generation of a transmission / reception timing interrupt and storing it in the received data storage means according to the set data transfer amount Data flow control method comprising a. The method of claim 3, wherein The data flow control, And repeating each time the transmission / reception timing interrupt occurs until the transmission bit rate is reset or the video service is terminated. In a synchronous video terminal device having a processor, A first function of setting a data transmission amount at a reference time according to the selected transmission bit rate; A second function of obtaining a threshold setting value in consideration of the storage capacity of the transmission data storing means; When the transmission / reception timing interrupt occurs, the amount of data stored in the transmission data storage means is compared with the threshold setting value, and if it is less than the threshold setting value, it waits until the next transmission / reception timing interrupt. A third function to process; And A fourth function of reading a received frame and storing it in the received data storing means according to the set data transfer amount when a transmission / reception timing interrupt occurs; A computer-readable recording medium having recorded thereon a program for realizing this.