JP2939933B2 - Communication system for time series information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for compressing and encoding time-series information such as moving images and voices for transmission and reception.
In particular, the present invention relates to a system for communicating time-series information of a quality corresponding to a system load without interruption of reproduction.

[0002]

2. Description of the Related Art In a conventional immediate-reproduction type time-series information communication system for transmitting and receiving information that changes in time series such as voice and moving images, the compression rate at the time of compression encoding is fixed and transmitted. I was In such an instant reproduction communication system, a buffer for temporarily storing the decoded time-series information is provided in the receiving apparatus, and the time-series information is reproduced without interruption. However, in this case, if the compression ratio is set too low, there is no decoded information in the buffer when the reproduction amount is large, that is, when the system load is large, and the reproduction may be interrupted. Conversely, if the compression ratio is set too high, there is a problem that only low-quality information can be communicated even when the system load is small.

In order to solve such a problem, a method has been proposed in which communication is performed by changing the compression ratio in a time-series manner according to the free space of a communication path. For example, "Tetsuo Tajiri, Toru Sakatani, Hiroshi Sosenji, Takashi Nishimura, Realization of Video Communication Service by CSMA / CD LAN, Information Processing Society of Japan Research Report 93
-AVM-2, 1993, pp. 9-16, a congestion control method has been proposed in which discarding of a packet is detected from the sequence number of the header portion of a video / audio data packet and the coding parameter is changed.

Further, there has been proposed a method of monitoring not only the state of a communication path but also the output state of a receiving apparatus to an output apparatus, and determining and changing an encoding parameter of a transmitting apparatus from the monitoring result (publicly disclosed). Patent publication 1993 268296
No.).

[0005]

However, in the above-mentioned conventional example, measures are not taken for all of the factors that affect the transmission / reception apparatus when performing immediate reproduction. For example, the maximum amount of information that can be handled by a communication system depends not only on the state of the communication path and the output state from the receiving device to the output device, but also on the capacity of the buffer of the receiving device. Is done. In other words, if the buffer capacity is low and it becomes empty,
Playback is interrupted. In addition, depending on the communication protocol, if the load on the communication path is at least, if the buffer of the receiving device does not have an empty space, the data overflows from the buffer, and necessary data is discarded, and accurate data cannot be reproduced. Inconvenience occurs.

Therefore, even when the free space in the buffer of the receiving apparatus is small, the data reproduction is not interrupted, that is, the data amount in the buffer is not emptied, and when the free space in the buffer has sufficient space. It has been desired to develop a system that can transmit and receive high-quality information accordingly.

In view of the above background, the present invention enables communication of time-series information of the highest possible quality according to the state of the system load, and communication of the time-series information without interruption of reproduction. The purpose is to provide a system.

[0008]

According to the present invention, there is provided a communication system for time-series information provided by a transmission device for compressing and encoding time-series information such as a moving image and a voice by a predetermined coding parameter and transmitting the compressed data to a communication path. A receiving device that decodes the compressed and encoded data received via the communication path and temporarily stores the decoded data in the buffer, and a reproducing device that extracts the decoded data temporarily stored in the buffer and reproduces the time-series information. A time-series information communication system, comprising: a data amount detection unit that detects a degree of change in a relative storage amount of decoded data in the buffer; and a compression rate of the compressed encoded data based on the detected value. Parameter determining means for determining the encoding parameter for dynamically changing.

In the time-series information communication system having the above-mentioned configuration, preferably, the parameter determining means dynamically adjusts a compression rate of the compressed coded data as the amount of decoded data stored in the buffer decreases. An encoding parameter having a value for dynamically decreasing the compression ratio when the compression ratio is increasing or increasing is determined. Alternatively, if the amount of decoded data stored in the buffer is equal to or less than a predetermined value with respect to the total buffer amount, the compression ratio is dynamically increased, and if the amount of decoded data is equal to or more than the predetermined value, the compression ratio is dynamically reduced. Determine the encoding parameters.

[0010]

In the communication system for time-series information according to the present invention, time-series information such as a moving image and audio is compression-encoded by a transmission device based on predetermined encoding parameters and transmitted to a communication channel. On the other hand, the receiving device decodes the compressed and coded data received via the communication path and temporarily stores the decoded data in a buffer. The playback device extracts the decoded data from the buffer and plays back a moving image, audio, or the like.

[0011] The decoded data in the buffer decreases every time it is extracted and reproduced by the reproducing means. However, since the compressed and coded data is sent from the transmitting device to the receiving device as needed and supplemented, continuous reproduction is possible. Extraction amount (data consumption amount) and replenishment amount (data supply amount) of decoded data for this buffer
The difference from this indicates indirectly the system load state or the processing capacity of the entire system.

Therefore, the data amount detecting means detects the degree of change in the relative storage amount of the decoded data in the buffer and sends it to the parameter determining means. This degree of change can be detected by an arbitrary numerical calculation method, but at least first numerical information obtained by dividing the accumulated amount of decoded data in the buffer at the time of extraction by the total amount of the buffer, and decoding at the time of the extraction and at the time of the previous extraction. Second obtained by dividing the difference of the storage amount of the coded data by the total buffer amount
Quantified by including the following numerical information.

The parameter determining means determines the detected value, in particular,
An encoding parameter for dynamically changing the compression rate of the encoded data is determined based on the first numerical information and the second numerical information. At this time, as the amount of decoded data stored in the buffer decreases, the compression ratio of the compressed encoded data is dynamically increased, and when the amount of the encoded data is increasing, the encoding parameter is dynamically reduced. To determine. As a result, the compression ratio dynamically changes according to the consumption and supply of the decoded data amount. Further, the encoding parameter is dynamically increased when the amount of decoded data stored in the buffer is equal to or less than a predetermined value with respect to the total amount of the buffer. By determining the value, the amount of decoded data in the buffer is stabilized at a predetermined value.
As a result, time-series information of quality according to the system load, that is, time-series information in which the compression ratio is dynamically changed is transmitted from the transmitting device, and the amount of decoded data in the buffer of the receiving device is substantially equal to the predetermined amount. Always secured.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a general communication system for time-series information to which the present invention is applied.
11 is a compression ratio control device, 12 is a receiving device, 13 is a communication channel, 14 is an information storage unit in which time-series information is stored in advance, 1
5 is an information input unit for inputting time series information from outside,
Reference numeral 16 denotes a reproduction unit (reproduction means) including a device driver, a speaker, and the like.

The transmitting device 10 includes an encoding unit (encoding means)
101 and a communication control unit 102, and the receiving device 12
The compression ratio control device 11 includes a communication control unit 121, a decoding unit (decoding unit) 122, and a buffer 123. The compression ratio control unit 11 includes a data amount detection unit (data amount detection unit) 111 and an encoding parameter change unit (parameter determination unit). 112 is provided.

In the communication system having the above-described configuration, the time-series information such as a moving image and a sound guided from the information storage unit 14 or the information input unit 15 to the transmitting apparatus 10 is compression-coded by the coding unit 101, and is further subjected to communication control. The data is transmitted to the communication path 13 via the unit 102. In the receiving device 12, the compressed and coded data received via the communication control unit 121 is decoded by the decoding unit 122 and temporarily stored in the buffer 123. The reproduction unit 16 extracts the decoded data stored in the buffer 123 as needed and reproduces a moving image, a sound, or the like.

The compression ratio control device 11 dynamically changes the compression ratio of the encoding unit 101 according to the degree of change in the relative storage amount of the decoded data in the buffer 123. That is, the data amount detection unit 111 detects how much the decoded data in the buffer 123 is increasing or decreasing, and what percentage of the buffer capacity the data amount occupies, and performs encoding. The parameter is sent to the parameter changing unit 112. The encoding parameter changing unit 112 determines an appropriate encoding parameter from the detected value and the current encoding parameter, and notifies the encoding unit 101 of the determined encoding parameter. In response to this, the encoding unit 101 dynamically changes the encoding parameter and changes the compression ratio of the time-series information. As a result, time-series information of a quality corresponding to the amount of data in the buffer 123 is sent to the receiving device 12 via the communication path 13.

Next, a music communication system according to an embodiment of the present invention will be described with reference to FIG. In FIG. 2, 2
1 is a server unit for transmitting music files, 22 is a sound quality control unit for controlling encoding parameters according to the load state of the communication system, 23 is a client unit for receiving and reproducing music files, and 24 is a communication path. In comparison with FIG. 1, the server unit 21 corresponds to the transmission device 10, the sound quality control unit 22 corresponds to the compression control device 11, and the client unit 23 corresponds to the reception device 12.

The server unit 10 includes a communication control unit 21 for performing packet assembly / disassembly and retransmission processing when a packet is discarded.
1. Request processing unit 2 for selecting a music file specified by a request sent from client unit 23
12, a variable DPCM encoding unit 213 that performs compression encoding,
And a music file storage unit 214 for storing music data files.

Here, DPCM (Differntial Pulse Code)
Modulation is a difference quantization, and refers to an information compression method that encodes the difference between adjacent samples with a small number of bits (“Sadahiro Furui, Digital Speech Processing, Tokai University Press, 1985, pp. 101-103 "). Variable DPCM
"DPCM" is a DPCM capable of dynamically changing the number of bits allocated to the expression of the difference between adjacent samples, that is, changing one piece of music data halfway. Also, variable DP
The coding parameter in the CM is the number of bits allocated to the expression of the difference between adjacent samples.

The sound quality control unit 22 is a communication control unit 22 for assembling and disassembling a packet and performing retransmission processing when a packet is discarded.
1. An allocation change unit 222 that determines an encoding parameter, a performance monitoring unit 223 that monitors system performance, and a previous data amount storage unit 224 that temporarily stores the data amount in the buffer 234. .

The client unit 23 assembles a packet.
A communication control unit 231 that performs disassembly and retransmission processing when a packet is discarded; a variable DPCM decoding unit 232 that functions as a decoding unit; a request generation unit 233 that specifies a music file and issues a transmission request to the server unit 21; Buffer section 234 for temporarily storing coded data, and buffer section 23
4 is provided with a playback device driver 235 that extracts music data from the speaker 4 and converts the music data into an electric signal that can be reproduced by the speaker 236.

Next, the operation of each section in the music communication system having the above configuration will be described in accordance with the following four flows. However, as an initial setting, an initial encoding parameter is given to the variable DPCM encoding unit 213, “0” is given to the previous data storage unit 224 for the data amount in the buffer, and the performance monitoring unit 223 sets the total buffer amount of the buffer 234. , And the buffer 234 is empty.

(1) Request Flow The request information generated in the request generation section 232 of the client section 23 is packetized by the communication control section 231 and arrives at the server-side communication control section 211 via the communication path 24. The communication control unit 211 decomposes the request information packet and
Send to The request processing unit 212 interprets the received request information, selectively extracts the requested music file from the music file storage unit 214, and sends the extracted music file to the variable DPCM encoding unit 213. The encoding parameters for the variable DPCM encoding unit 213 are set to certain initial values.

(2) Music Data Flow Next, the variable DPCM encoding unit 213 encodes the received music data according to the encoding parameters. The encoded music data is packetized by the communication control unit 211 and decomposed by the communication control unit 231 on the client side through the communication path 24. The music data decomposed into packets is decoded by the variable DPCM decoding unit 232 and is sequentially stored in the buffer 234.

(3) Flow of Playback In the playback, the music data stored in the buffer 234 has a reference value (for example, 80% of the total buffer capacity of the buffer 234).
Is started at the time when the above is exceeded. At this time, the reproduction device driver 235 receives the music data from the buffer 234, performs processing such as D / A conversion and amplification, and sends the data to the speaker 236 as an electric signal. The speaker 236 reproduces the electric signal as music that can be heard by humans.

(4) Flow of sound quality control The sound quality control is performed asynchronously with the flow of the above (1) to (3). That is, the performance monitoring unit 22 of the sound quality control unit 22
3 periodically receives from the buffer 234 information on the total buffer amount and the amount of music data in the buffer. At this time, information on the total buffer amount and the amount of music data in the buffer is packetized by the communication control unit 231 on the client side, and decomposed into packets by the communication control unit 221 on the sound quality control side via the communication path 24. Before receiving the information on the total buffer amount and the amount of music data in the buffer, the performance monitoring unit 223 accumulates the previously received music data amount in the buffer in the previous buffer data amount storage unit 224.

The performance monitor 223 is obtained by dividing the current buffer data amount by the total buffer amount (first numerical information).
And a value obtained by dividing the difference between the previous buffer data amount and the current buffer data amount by the total buffer amount (second numerical information) to the allocation change unit 222 as numerical information representing the performance of the system. I do. The allocation changing unit 222 determines an encoding parameter from these pieces of information. The encoding parameter can be determined by any method. In this embodiment, the following method is used.

It is assumed that the number of quantization bits of the music data is 16 bits, and the encoding parameter, that is, the number of bits allocated to the difference between adjacent samples takes a value in the range of "3" to "15". The current parameter is P0, the encoding parameter to be obtained is P1, the current buffer data amount divided by the total buffer amount is V, and the difference between the previous buffer data amount and the current buffer data amount is the total buffer amount. When the division is D, the encoding parameter is determined by Equation 1.

[0030]

P1 = P0-10 (V-0.8) -20D where P1 = 3 when P1 <3 and P1 when P1> 15
= 15. In equation (1), −10 (V−0.8) has a role of stabilizing the data amount in the buffer unit to 80% of the total buffer amount, and −20D has a role of suppressing an increase or decrease in the data amount in the buffer unit.

The coding parameters obtained in this manner are packetized by the communication control
The packet is decomposed by the communication control unit 211 on the server side through 4 and passed to the variable DPCM encoding unit 213. The variable DPCM encoding unit 213 encodes the next music data based on the passed encoding parameters.

As described above, according to the present embodiment, the quality of the music data sent from the server unit 21 is dynamically changed in packet units according to the system load state. A predetermined amount of decrypted data is always secured. As a result, the music data can be reproduced without interruption in the client section 23, and the conventional problem is solved.

The above description shows one embodiment of the present invention, and it is needless to say that the present invention should not be limited to the above embodiment. For example, in the present embodiment, the music data is supplied from the music file storage unit 214, but may be directly input from outside the apparatus. However, in an instant-reproduction-type music communication system that supplies music through a communication path from a file storing a large amount of music data, care must be taken so that the reproduction of music is not interrupted.

Further, the server unit 21, the sound quality control unit 22, and the client unit 23 in the present embodiment can exist in any computer connected via the communication path 24. For example, the server unit 21, the sound quality control unit 22, the sound quality control unit 22 exists in the server unit 21 or the client unit 23, or the like.
It is possible that two or three of the client units 23 exist in the same computer.

Further, in the above-described embodiment, the music information data and other data such as control information are both transmitted and received through the same communication path 24, but these are transmitted and received through separate communication paths. May be
Alternatively, a plurality of communication paths may be selectively used.

[0036]

As is apparent from the above description, in the time-series information communication system of the present invention, the degree of change in the relative storage amount of decoded data in the buffer is detected, and compression is performed based on the detected value. Since the configuration is such that the encoding parameter for dynamically changing the compression ratio of the encoded data is determined, there is an effect that the amount of information to be transmitted dynamically changes according to the amount of data in the buffer.

In particular, as the amount of decoded data stored in the buffer decreases, the compression ratio of the compressed coded data is dynamically increased, and when the amount is increasing, the compression parameter is dynamically reduced. When the amount of decoded data stored in the buffer is small, the compression rate is increased and long time-series information can be transmitted. On the other hand, the decoded data stored in the buffer can be transmitted. When the amount is large, the compression ratio is set low, so that higher quality time-series information can be transmitted and received. Also, if the amount of decoded data stored in the buffer is equal to or less than a predetermined value with respect to the total buffer amount, the compression ratio is dynamically increased, and if the amount is greater than or equal to the predetermined value, the encoding parameter is dynamically reduced. In the configuration that determines
It is possible to prevent a situation where there is no more decoded data to be reproduced in the buffer.

As described above, according to the present invention, it is possible to realize a system capable of communicating time-series information having a quality according to the load state of the system without interruption.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a general communication system to which the present invention is applied.

FIG. 2 is a configuration diagram of a music communication system according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Transmitting apparatus 101 Encoding unit (encoding unit) 102 Communication control unit 11 Compression ratio control unit 111 Data amount detecting unit (data amount detecting unit) 112 Encoding parameter changing unit (encoding parameter determining unit) 12 Receiving device 121 Communication Control unit 122 Decoding unit (decoding means) 123 Buffer 13 Communication path 14 Information storage unit 15 Information input unit 16 Reproduction unit (reproduction device)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-29442 (JP, A) JP-A-63-15559 (JP, A) JP-A-7-170503 (JP, A) JP-A-7-170 170292 (JP, A) JP-A-4-297179 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04L 13/08

Claims (4)

(57) [Claims] 1. A transmitting apparatus for compressing and encoding time-series information such as a moving image and a sound with a predetermined encoding parameter and transmitting the compressed and encoded data to a communication path, decoding the compressed and encoded data received through the communication path, and A communication system for time-series information, comprising: a reception device that temporarily stores the data in a buffer; and a reproduction device that extracts the decoded data temporarily stored in the buffer and reproduces the time-series information. Data amount detecting means for detecting the degree of change in the relative storage amount of data, and parameter determining means for determining the encoding parameter for dynamically changing the compression ratio of the compressed encoded data based on the detected value A communication system for time-series information, comprising: 2. The communication system for time-series information according to claim 1, wherein the parameter determining unit dynamically changes a compression ratio of the compression-encoded data as the amount of decoded data stored in the buffer decreases. A communication system for time-series information, wherein a coding parameter of a value to be increased is determined. 3. The communication system for time-series information according to claim 1, wherein said parameter determining means dynamically adjusts the compression rate when the amount of decoded data stored in said buffer is increasing. A communication system for time-series information, wherein an encoding parameter of a value to be decreased is determined. 4. The communication system for time-series information according to claim 1, wherein the parameter determining unit determines that the compression rate is smaller than a predetermined value with respect to a total buffer amount. A time-series information communication system, wherein a coding parameter of a value which is dynamically increased and the compression ratio is dynamically decreased when the compression ratio is equal to or more than a predetermined value is determined.