JP2000307638A - Receiving buffer controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device capable of realizing a stable stream reproducing function by allowing a client to automatically manage a receiving buffer size. SOLUTION: A client automatically manages a receiving buffer size in this constitution. In this receiving buffer controlling device, a receiving buffer 101 temporarily stores data in a buffer. A storing pointer (RECP) 103 shows a position in a buffer where stream data to be received next should be stored. A reproducing pointer (PLAYP) 104 shows the position in the buffer of stream data which should be reproduced next. A buffer pointer managing part 105 manages the positions of the pointer (RECP) and the pointer (PLAYP) 104. A reproducing part 106 decodes (reproduces) the received data. A receiving buffer managing part 107 manages the size of the receiving buffer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a client system connected to a video server for distributing video, audio, etc., capable of performing stable stream reproduction.
In addition, the present invention relates to a stream data reception buffer control device that reduces the effort required when designing a client and enables the construction of a versatile client system.

[0002]

2. Description of the Related Art In a so-called VOD (video on demand) system in which stream data is transmitted to a client from a video server that distributes video, audio, and the like and is played back (displayed) on the client side, a stable stream of Important factors for obtaining reproduction include (1) data transmission stability (server side), (2) reliability and bandwidth of communication medium, and (3) data reception and reproduction capability (client side). Here, attention is paid to (3).

[0003] In a general VOD system, a client that receives stream data such as video data and audio data holds a data reception buffer regardless of whether the reproduction method is software or hardware. The stream sent through the communication medium,
The data is temporarily stored in the data reception buffer, and then the data in the buffer is subjected to appropriate processing and reproduced.

Now, suppose that the transmission from the video server is stable, and a network such as a LAN is used as a communication medium for the stream. At this time, in order to perform stable reproduction on the client, it is necessary to absorb fluctuations and delays of stream data peculiar to the network. In addition, errors may occur in the reproduction bit rate of the stream due to the difference in clock precision between the server side and the client side, which may cause a slight deviation, and this also needs to be adjusted. A technically important factor here is the size of the stream data receiving buffer on the client side.

For example, if the buffer size for receiving data is too small, buffer overflows and underflows frequently occur due to instability such as fluctuations in communication and deviation in the reproduction bit rate, and the reproduction of the stream is extremely unstable. become. Conversely, if the buffer size for data reception is too large, buffer overflows and underflows will decrease, but the amount of memory used by the client system will increase significantly, and the stream playback processing itself and other processing will be performed. , The load on the entire client system increases, and as a result, stream reproduction becomes unstable.

Conventionally, in order to avoid such a problem, a buffer size for data reception is determined by a client system designer analyzing the performance of a communication medium and a client at the time of designing a VOD system, and considering the overall balance. Then, an appropriate value was fixedly assigned in advance.

[0007]

However, in the current situation of diversifying VOD systems, this method requires a designer to spend a great deal of effort on analysis in order to respond best to each client. Since the buffer size for data reception is fixed, the flexibility of system construction is lacking. As described above, it is difficult to construct a general-purpose client system in the conventional method.

[0008] As described above, in a client system connected to a video server that distributes video, audio, and the like, when allocating a stream receiving buffer size for realizing stable stream reproduction, a conventional method employs a system. At the time of design, the designer analyzed performance for each client and fixedly set an appropriate buffer size. Therefore, there is a problem that it takes time to construct a more suitable client system, and it is difficult to construct a general-purpose client system.

In view of the above, the present invention realizes a stable stream reproduction function in a client system connected to a video server for distributing video, audio, etc., and reduces the effort at the time of client design. Also,
It is an object of the present invention to provide a stream data reception buffer control device capable of constructing a versatile client system.

[0010]

Therefore, according to a first aspect of the present invention, there is provided a receiving buffer for storing received stream data, and a method for reproducing the stream data stored in the receiving buffer. A predetermined length of time between reproduction means, a storage pointer indicating a position in the reception buffer for storing stream data to be received next, and a reproduction pointer indicating a position in the reception buffer to be reproduced next by the reproduction means. Calculating a size of the reception buffer using one of the maximum value and the minimum value calculated by the difference calculation means for calculating the maximum value and the minimum value of the difference in Means for changing the size of the reception buffer to a required size when reproducing stream data by means of That the reception buffer control unit is.

[0011] According to such a reception buffer control device, the difference calculation means uses one of the maximum value and the minimum value of the difference between the storage pointer and the reproduction pointer within a predetermined period of time to overflow or underflow. Can determine the size of the receive buffer that does not
Since the size of the reception buffer is changed to the obtained size of the reception buffer, the stream data can be stably reproduced.

According to a second invention, in the first invention, in the first invention, N is a constant, X is a bit rate of stream data, and M is a ratio (%) of the reproduction pointer to the reception buffer size. ) And D are N * X + | N * X * M / 100 among the maximum and minimum values of the difference.
−D | where the difference is larger, the following equation (reception buffer size) = N * X + | N * X * M / 100−
D | (bit).

According to such a reception buffer control device, the size of the reception buffer can be obtained according to a predetermined equation.

Further, according to the third invention, a receiving buffer for storing the received stream data, a reproducing means for reproducing the stream data stored in the receiving buffer, and a stream data to be received next. A maximum value and a minimum value of a difference within a predetermined time between a storage pointer indicating a position in the reception buffer for storing the position in the reception buffer and a reproduction pointer indicating a position in the reception buffer to be reproduced next by the reproduction means are obtained. An error between the storage pointer and the reproduction pointer within a predetermined time is obtained by using a difference calculation unit and one of the maximum value and the minimum value calculated by the difference calculation unit. Means for changing the size of the reception buffer based on an error.

According to such a reception buffer control device, using either one of the maximum value and the minimum value calculated by the difference calculation means, the storage pointer and the reproduction pointer can be determined within a predetermined time. Since the error is obtained and the size of the receiving buffer is changed based on the obtained error, the difference in clock accuracy between the server and the client can be absorbed, and stream reproduction with less waste of memory can be performed.

According to a fourth aspect of the present invention, in the third aspect, the error is such that N is a constant, X is the bit rate of stream data, M is the ratio (%) of the reproduction pointer to the reception buffer size, T Is a fixed time, and D is N * X + | N * X * M / 100 among the maximum value and the minimum value of the difference.
−D |, the difference is larger, and the receiving buffer is obtained according to the following equation (error) = X * (| N * X * M / 100−D |) / T It is a control device.

According to such a reception buffer control device, the size of the reception buffer can be obtained according to a predetermined equation.

[0018]

FIG. 1 is a diagram showing a VOD system in which a receiving buffer control device of the present invention is used.

In this VOD system, MPEG
Video server 1 that transmits video and audio data compressed as such as stream data, and clients 3a to 3d that decode and reproduce the transmitted stream data.
3c is connected via the network 2.

Here, it is assumed that the stream transmission from the server is stable, and that the client performs decoding (reproduction) in synchronization with the clock of the server. In this case, what hinders stable stream reproduction is mainly network communication fluctuation.

The reception buffer control device according to the first embodiment of the present invention reproduces stream data stably in such an environment.

FIG. 2 is a diagram showing a reception buffer control device according to the first embodiment of the present invention. This reception buffer control device is provided in the client shown in FIG.

As shown in FIG. 1, the receiving buffer control device of the present embodiment comprises a stream data receiving buffer 10.
1, reception buffer storage unit 102, storage pointer 103,
Reproduction pointer 104, buffer pointer management unit 105
And a reproducing unit 106.

The receiving buffer 101 temporarily stores the received stream data.

The reception buffer storage unit 102 stores the received data in a buffer.

The storage pointer (RECP) 103 indicates the position in the buffer where the stream data to be received next is to be stored.

A reproduction pointer (PLAYP) 104 indicates a position in the buffer of the stream data to be reproduced next.

The buffer pointer management means 105 includes a storage pointer (RECP) and a reproduction pointer (PLAY).
Manage the position of P).

The reproducing unit 106 decodes (reproduces) the received data.

The reception buffer management unit 107 manages the size of the reception buffer.

Next, the reproduction bit rate Xbps is sent from the server.
The operation flow when the stream data is transmitted to the client will be described. First, the client secures a buffer of N times the bit rate of the stream by the reception buffer management unit 107 (N * Xbit), and starts receiving data.

Next, when data is received, the reception buffer storage unit 102 stores the data in the reception buffer 101,
The RECP is advanced in the buffer by the received data amount.
The data reception is repeated in this manner, and the RECP is M% of the reception buffer size (N * X * M / 100 bits).
When the playback buffer 106 reaches the reception buffer 101,
Start the playback process from the beginning of the.

The reproducing unit 106 advances the PLAYP in the buffer by the reproduced data amount. However, RECP
And PLAYP do not exceed the size of the receiving buffer, and when reaching the end of the receiving buffer, reset to the beginning (0) of the buffer and control to store or reproduce data from there.

The above is the basic operation. If there is no fluctuation in the communication of the stream on the network at this time, the data in the reception buffer always has a margin of (100-M)% of the buffer size. Should be played back stably.

However, since the data flowing on the network may be frequently stagnant or suddenly flow in large amounts, the data may overflow (R) in the reception buffer.
ECP may overtake PLAYP) or underflow (PLAYP overtakes RECP).

Moreover, the frequency of occurrence increases in proportion to the length of the stream (reproduction time). If a huge amount is secured in the receiving buffer in advance, the frequency of occurrence can be reduced. However, the client consumes a large amount of resources only by increasing the reception buffer, which increases the load and deteriorates the memory use efficiency.

Therefore, in the present embodiment, control is performed so as to perform the following operation in addition to the above basic operation.

That is, while the stream data is being received / reproduced according to the basic operation described above, the buffer pointer management unit 105 always keeps the RECP and PLAYP
Is monitored and the maximum value Dmax (bit) is monitored.
And the minimum value Dmin (bit) are recorded in a file or a memory.

Then, when the stream is reproduced next, first, the reception buffer management unit 107 uses these values to determine the data reception buffer size by the following equation.

N * X + | N * X * M / 100−D | (bit) (1) where D is (N * X * M / 1) of Dmax and Dmin.
00) is larger (the value in || is an absolute value).

Then, | N * X * M / 100-D in the above equation
Only when the value of | exceeds the threshold A, reproduction is performed by using the reception buffer size obtained here (the threshold A is, for example, N * X / 2).

That is, here, the portion of || in the above equation is defined as communication fluctuation, and the reception buffer is increased only when the communication is largely changed, and then the stream is received / reproduced. . As a result, when the reception buffer has an appropriate size, the value of || hardly exceeds the threshold value A, and it becomes stable.

By controlling the receiving buffer size in this manner, the number of times of buffer overflow or underflow is reduced, and more stable stream reproduction can be automatically obtained. Also, by setting the initial value of N small, it is possible to secure a reception buffer size more suitable for the execution environment (network condition), and to improve the resource utilization efficiency of the client.

Therefore, according to the reception buffer management device of the present embodiment, the client automatically manages the size of the stream reception buffer, so that in the VOD system using the network, the design of the client can be performed without trouble. , More stable stream reproduction suitable for the environment.

Next, a second embodiment of the present invention will be described.

In the present embodiment, V in FIG.
In an OD system, it is assumed that the video server stream transmission is stable and the network bandwidth is sufficient and does not fluctuate, but the client and server operate asynchronously and completely independently on their respective clocks.

FIG. 3 is a diagram showing a receiving buffer control device according to a second embodiment of the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

That is, the difference between the reception buffer control device of the present embodiment and the reception buffer control device of the first embodiment is that an error detection unit 201 is provided.

The flow of the operation when the stream data of the bit rate Xbps is transmitted from the server and received / reproduced by the client will be described below.

The basic operation is the same as that of the first embodiment, but the main difference is the function of the error detection unit at the time of stream reception / reproduction.

First, the client secures a buffer N times the bit rate of the stream by the reception buffer management unit 107 (N * X bit), and starts receiving data.

Next, the reception buffer storage unit 102 stores the data in the reception buffer 101, and advances the RECP in the buffer by the received data amount. By repeating this, RECP becomes M% (N * X * M) of the reception buffer size.
/ 100 bits), the reproduction unit 106 starts reproduction processing from the beginning of the reception buffer 101.

The reproducing unit 106 advances the PLAYP in the buffer by the reproduced data amount. During the reproduction of the received data, the buffer pointer management unit 105 constantly monitors the difference value between RECP and PLAYP, and stores the maximum value Dmax (bit) and the minimum value Dmin (bit) in a file or a memory. To record.

The error detecting section 201 has a predetermined time T
At the end of (seconds) playback, using the recorded value and values such as bit rates X and M,
An error DF at a fixed time T is obtained. The error DF means a difference between RECP and PLAYP due to a difference in clock cycle between the client and the server.

DF = X * (| N * X * M / 100−D |) / T (2) where D is (N * X * M / 1) of Dmax and Dmin.
00) is larger.

Since the obtained error DF is an error due to a difference in clock precision occurring during a certain time when this stream is reproduced, the reproduction time of the entire stream is now set to ET.
Then, the final error when the reproduction is completed is DF * ET / T (bit) (3).

That is, if a buffer is initially reserved for the value of this expression, no overflow or underflow will occur. Therefore, at the time of the next stream reproduction, the reception buffer management unit 107 obtains and secures the reception buffer size by the above equation, and reproduces the stream.

By controlling the receiving buffer size in this way, it is possible to absorb the difference in clock accuracy between the server and the client and to perform stream reproduction with less waste of memory usage.

Therefore, according to the reception buffer management apparatus of the present embodiment, the client automatically manages the reception buffer size, so that the client does not have to worry about the difference in clock accuracy between the server and the client, and can easily use the general purpose. You can build highly efficient and efficient clients. Also, a more stable reproduction of the stream can be performed.

[0060]

As described above in detail, according to the present invention,
In a client system connected to a video server that distributes video, audio, and the like, a stable stream reproduction function can be realized, the labor required when designing the client can be reduced, and a versatile client system can be constructed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a V used in a reception buffer control device of the present invention.
The figure which shows an OD system.

FIG. 2 is a diagram showing a reception buffer control device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a reception buffer control device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Video server which transmits data, such as MPEG, 2 ... Network 3a-3c ... Client 101 ... Stream data receiving buffer 102 ... Receiving buffer storage unit 103 ... Storage pointer (RECP) 104 ... Playback pointer (PLAYP) ), 105: buffer pointer management unit, 106: reproduction unit, 107: reception buffer management unit, 201: error detection unit.

Continued on the front page F-term (reference) 5B089 GA18 GA23 GB01 HA06 JA33 JB04 JB05 KA09 KA12 KB04 KD01 5C059 KK34 RC32 SS09 SS30 TA71 TC15 TD05 TD11 UA05 UA32 UA36 UA38 5K030 GA11 HA07 HB01 HB03 HC01 JT02KA 01 LD EE09 FF13 HH13 9A001 BB03 CC02 CZ08 JJ20 JJ27

Claims (4)

[Claims] 1. A receiving buffer for storing received stream data, a reproducing unit for reproducing the stream data stored in the receiving buffer, and a receiving buffer for storing stream data to be received next. Difference calculating means for obtaining a maximum value and a minimum value of a difference between a storage pointer indicating a position and a reproduction pointer indicating a position in the reception buffer to be reproduced next by the reproduction means within a predetermined time; The size of the reception buffer is obtained by using one of the maximum value and the minimum value calculated by the means, and the size of the reception buffer is obtained by reproducing the stream data by the reproduction means. A receiving buffer control device. 2. The size of the reception buffer is as follows: N is a constant, X is the bit rate of stream data, M is the ratio (%) of the playback pointer to the reception buffer size, and D is
Is N * X + | N * X * M among the maximum value and the minimum value of the difference.
/ 100−D |, the larger the difference, the following equation (reception buffer size) = N * X + | N * X * M / 1
2. The reception buffer control device according to claim 1, wherein the reception buffer control device is obtained according to the following formula: 00-D | (bit). 3. A receiving buffer for storing received stream data, a reproducing means for reproducing the stream data stored in the receiving buffer, and a receiving buffer in the receiving buffer for storing stream data to be received next. Difference calculating means for obtaining a maximum value and a minimum value of a difference between a storage pointer indicating a position and a reproduction pointer indicating a position in the reception buffer to be reproduced next by the reproduction means within a predetermined time; Using one of the maximum value and the minimum value calculated by the means, an error between the storage pointer and the reproduction pointer within a certain period of time is obtained, and based on the obtained error, the reception buffer of the reception buffer is obtained. Means for changing the size. 4. The error is as follows: N is a constant, X is the bit rate of stream data, M is the ratio (%) of the playback pointer to the receive buffer size, T is a fixed time, and D is the maximum value and the minimum value of the difference. N * X + | N * X * M / 1
When the difference from 00-D | is larger, the difference is obtained according to the following equation (error) = X * (| N * X * M / 100-D |) / T. Item 3. The reception buffer control device according to Item 3.