JPH10108160A - Data distribution system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the data distribution system in which it is not required for a client to take synchronization by distributing optimum bit streams without distributing useless data to a channel. SOLUTION: In the image distribution system where a server generates a bit stream obtained by interleaving image data and voice data in response to a transmission request from a client and sends the stream to the client, the client sends (step 103) a DC value denoting a decoding capability together with a transmission request (step 101). The server controls a production amount of the bit stream so that the received DC value is not exceeded (steps 207, 208). Since it is not required to send useless stream that is unable to be decoded, no excess data are distributed through a channel. Moreover, the client takes tacit synchronization between the voice and image data, then no adjustment of synchronization is required.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data distribution system, and more particularly to a data distribution system for distributing a moving image together with audio from a server to a client via a line.

[0002]

2. Description of the Related Art Conventionally, in a data distribution system for transmitting moving image data using a line, the line is usually at a low bit rate, and therefore, transmission is performed after compression encoding. Therefore, the receiving side (client) needs to be provided with decoding means for decoding the compression-encoded moving image data, and to decode the received data. Conventionally, when audio data transmitted together with the above-mentioned moving image data is interleaved, it is necessary to transmit the moving image data in synchronization with the audio data.

[0003]

In the above-mentioned conventional data distribution system, if the decoding capability of the client cannot process the transferred data, the reproduction will be delayed if all the transmitted images are decoded. It is necessary to skip one image decoding as needed. In such a case, data that could not be decoded also flows on the line, that is, useless data flows on the line, resulting in line congestion. In addition, a circuit for adjusting synchronization between image data and audio data is required on the client side.

[0004] Further, when the traffic on the line is congested, data transmission is not sufficiently performed, so that voice may be interrupted or time required for transmitting one piece of data may be too long. .

[0005] The present invention has been made in view of the above points,
An object of the present invention is to provide a data distribution system capable of distributing an optimal bit stream without flowing useless data through a line.

It is another object of the present invention to provide a data distribution system which does not require synchronization on the client side.

[0007]

According to the present invention, in order to achieve the above object, a server generates a bit stream in which image data and audio data are interleaved in response to a transmission request from a client and transmits the bit stream to the client. In the distribution system, the client has transmission means for transmitting the decoding capability value to the server together with the transmission request, and the server has control means for controlling the generation amount of the bit stream to be transmitted according to the received decoding capability value. Features.

Further, the server according to the present invention has encoding means for intra-frame encoding of a moving image, and the control means includes a number of images per unit time to be encoded by the encoding means so as not to exceed a decoding capability value. To determine or
Alternatively, the number of images to be read from the storage means per unit time is determined so as not to exceed the decoding capability value,
Alternatively, image data to be transmitted is selected from a plurality of types of moving image data.

Further, the server according to the present invention is characterized in that the server multiplies the ratio of the sum of the decoding capability values from all the accessing clients to the decoding capability value of one client transmitting the bit stream by the permissible line capacity. Is allocated as a line occupied bit amount and transmission is performed.

In the present invention, since the value indicating the decoder capability of the client is transmitted to the distribution server in advance, the distribution server can transmit an optimal stream to the decoder of the client. In the present invention, since the client receives only data that can be decoded, it is not necessary to consider skipping an image due to a delay in decoding.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of a server of a data distribution system of the present invention, and FIG. 2 is a block diagram of one embodiment of a client of the data distribution system of the present invention. In this data distribution system, one server and a plurality of clients are connected via a public line or a local area network (LAN).
This is a system in which a server transmits and distributes image data and audio data related to moving images in the form of a bit stream signal in real time in response to a connect request from a client.

As shown in FIG. 1, the server (distribution) side includes a control unit CPU (central processing unit) 11, a transmission unit 12, a reception unit 13, a stream generation unit 14, an image data storage unit 15,
The audio data storage unit 16 and the DC (Decode) of the client
r Capacity) memory 17 is connected via a bus 18.

The control unit CPU 11 controls each part of the server. The transmission unit 12 transmits image data and audio data. The receiving unit 13 receives image data and audio data from outside. The stream generation unit 14 is a circuit unit that interleaves image data and audio data, and can select the number of image data per second.
The image data storage unit 15 stores moving image data that has been compression-encoded by intra-frame compression (intra-picture of MPEG, JPEG, or the like).

The audio data storage unit 16 stores, for example, raw sampling data, audio data compressed and encoded by MPEG1 audio, DPCM, or the like. The memory 17 for storing the DC value of the client stores the decoding capability value (hereinafter, referred to as “DC”) transmitted by the accessing client.

On the other hand, the client, as shown in FIG.
The control unit CPU 21, the reception unit 22, the transmission unit 23, the audio decoder unit 24, and the image decoder unit 25
The audio decoder unit 24 is connected to a speaker 26, and the image decoder unit 25 is connected to a monitor 27. The control unit CPU 21 integrally controls each unit of the client. The receiving unit 22 receives the data,
3 transmits data. The audio decoder 24 decodes the received audio data. The image decoder unit 25 has a numerical value indicating a decoder capability, and notifies the server side as a distribution side of the numerical value, thereby receiving a bit stream having an optimum processing amount for the decoder from the server side. Has been made possible.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described with reference to the flowchart of FIG. When the client requests the server to transmit a moving image, the client first makes a connect request to the server (step 101). The server monitors whether there is a connect request (step 201). When there is a connect request, after transmitting a response from the transmission unit 12 (step 202), it checks whether DC is received (step 201). Step 203).

When the client confirms the reception of the response (step 102), the DC indicating the decoding capability is transmitted from the transmission unit 23 to the server (step 103). As the DC indicating the decoding capability, for example, an average decoding time (microsecond unit) of one macroblock of an I picture is used.

When the server confirms that the DC has been received by the reception unit 13, the server stores the received DC value and the address of the client in the DC value storage memory 17, and transmits a response from the transmission unit 13 to the client. (Step 204). When the client confirms receipt of this response (step 104),
An AV stream is requested (step 105).

When the server confirms that the AV stream request has been received (step 205), after transmitting a response (step 206), the control unit CPU 11
, The decoding time required for one image encoded in a frame is estimated, and the number N of moving images per second (images / second) is determined (step 207). For example, if the above DC value is "
For a 400 "client, the size 352 x 240 (3
30 macroblocks), one I
The time it takes to decode the picture is 13200
Since 0 (= 330 × 400) microseconds, the number of sheets per second is 7.57 (= 1,000,000 / 13200).
0), and N = 7.

The stream generation unit 14 transmits the audio data from the audio data storage unit 16 and the image data read from the moving image data storage unit 15 so that the number of images per second becomes N, while interleaving them. Part 1
2 to the client side (step 208). Further, the stream generation unit 14 monitors whether the data of the audio data and the image data is at the end (step 209). When confirming the end of the data, the stream generation unit 14 generates an EOF indicating the end of the data and transmits it. It is transmitted via the unit 12 (step 210).

On the client side, after confirming that a response which is a response from the server has been received after the AV stream request (step 106), the stream distributed from the server is transferred to the audio decoder unit 24 and the image decoder unit 25. To decode (step 10
7). The audio signal decoded by the audio decoder unit 24 is sounded by a speaker 26, and the video signal decoded by the image decoder unit 25 is displayed on a monitor 27 as an image. The above-described decoding operation of the received data is performed until it is confirmed that the EOF is received (step 10).
8).

Here, since the received bit stream is optimal for the respective capabilities of the audio decoder unit 24 and the image decoder unit 25, the decoding of the video does not delay the audio. Therefore, since the audio and the image can be implicitly synchronized, the function of synchronizing on the decoding side becomes unnecessary.

This can also cope with a case where the line is congested. If the distribution server has excessive access, it will exceed the server's permissible sending capacity. Therefore, a sufficient bit stream may not be delivered. Therefore, the permissible amount is set based on the state of the permissible amount of the line and the decoding capability value DC of each client. For example, the line capacity of the distribution server is M bits / s
And the clients C1, C to the distribution server.
2,. . . , Cn are accessing. And
The decoding capability value of each client (in this case,
The time for decoding one macroblock of an average I picture) is DC1, DC2,. . . , DCn, the bit amount Mi allocated to one client Ci is represented by the following equation.

Mi = M × ｛DCi / (DC1 + DC2)
+. . . + DCn)｝ The control unit CPU 11 transmits data while controlling the transmission bit rate for the client Ci so as not to exceed Mi.

After receiving the EOF, the client issues a disconnection request to the server (step 109), and receives a response from the server (step 110) to terminate the transmission / reception of the moving image. When a disconnection request is made (step 211), the server transmits a response (step 212), disconnects the line, and ends the processing.

The present invention is not limited to the above embodiment. For example, the server determines the number of images to be encoded per unit time by the encoding means so as not to exceed the DC value. Alternatively, a plurality of types of moving image data to be transmitted may be stored, and image data to be transmitted may be selected from the plurality of types of moving image data so as not to exceed the DC value.

[0028]

As described above, according to the present invention,
By transmitting the value indicating the client's decoder capability to the distribution server in advance, the distribution server transmits the optimal stream to the client's decoder, so that it is not necessary to transmit an excessive stream that cannot be decoded. It is not necessary to transmit useless data.

Further, according to the present invention, the client receives only enough data to be decoded and does not need to consider skipping the image due to a delay in decoding, so that the audio and the image can be implicitly synchronized. The configuration can be simplified as compared with the conventional configuration because no circuit is required for the configuration.

Further, according to the present invention, in the case of excessive access, a line capacity is allocated according to the ratio of the decoding capability of the client, and a stream is generated within that range. Can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of an embodiment of a client according to the present invention.

FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 control unit CPU (central processing unit) (control means) 12 transmission unit 13, 22 reception unit 14 stream generation unit 15 image data storage unit (storage means) 16 audio data storage unit 17 memory for storing DC value of client 18, 28 Bus 21 control unit CPU (central processing unit) (transmission unit) 23 transmission unit (transmission unit) 24 audio decoder unit 25 image decoder unit 26 speaker 27 monitor

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 7/045

Claims (5)

[Claims] 1. In response to a transmission request from a client,
In a data distribution system in which a server generates a bit stream in which image data and audio data are interleaved and transmits the bit stream to the client, the client includes a transmission unit that transmits the decoding capability value to the server together with the transmission request, A data distribution system, wherein the server has control means for controlling a generation amount of the bit stream to be transmitted according to the received decoding capability value. 2. The server has encoding means for intra-frame encoding of a moving image, and the control means is configured to encode the moving image per unit time by the encoding means so as not to exceed the decoding capability value. 2. The data distribution system according to claim 1, wherein the number is determined. 3. The server has storage means for storing image data obtained by intra-frame encoding of a moving image, and the control means sets an image unit to be read from the storage means so as not to exceed the decoding capability value. 2. The data distribution system according to claim 1, wherein the number of sheets per time is determined. 4. The server stores a plurality of types of moving image data to be transmitted, and the control unit selects image data to be transmitted from the plurality of types of moving image data so as not to exceed the decoding capability value. The data distribution system according to claim 1, wherein: 5. The server multiplies a ratio of a sum of the decoding capability values from all the clients accessing the decoding capability value of one client transmitting a bit stream to an allowable capacity of a line. 2. The data distribution system according to claim 1, further comprising means for allocating a value as a line occupied bit amount and performing transmission.