JP2004023548A - Distribution rate change method for streaming service, stream distribution server, stream distribution program, and information recording medium therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distribution rate change method for a streaming service, a stream distribution server, a stream distribution program and an information recording medium therefor in which the deterioration of reproduction quality when switching a bit rate is reduced. <P>SOLUTION: When the quality of stream distribution is lowered by the congestion of a network or the like, in the case of changing the stream distribution of a first bit rate BRa for compressed data of first compressibility CRa to the stream distribution of a second bit rate BRb for compressed data of second compressibility CRb, the stream distribution of the second bit rate BRb is performed for compressed data of third compressibility CRc and continuously, the stream distribution of a third bit rate BRc for the compressed data of the third compressibility CRc and the stream distribution of a fourth bit rate BRb' for the compressed data of the second compressibility CRb are concurrently performed. Afterward, the stream distribution is switched to only the stream distribution of the second bit rate BRb for the compressed data of the second compressibility CRb. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a streaming service distribution rate changing method, a stream distribution server, a stream distribution server, and a stream distribution program that reduce the influence of quality degradation due to congestion or the like when providing a streaming service in a network where a large number of users coexist, such as the Internet. It relates to an information recording medium.
[0002]
[Prior art]
Conventionally, in providing a streaming service for distributing data such as video and music from a stream distribution server to a client terminal via a multi-person best-effort network such as the Internet, the influence of other communications, such as congestion, etc. May cause quality degradation.
[0003]
In order to avoid this, the stream distribution server for sound data and video data determines the congestion state by a method such as confirming the communication state with the client terminal, and the control of the distribution server as shown in FIG. Thus, a function for dynamically changing between modes A and B having different bit rates is often provided.
[0004]
In recent years, a well-known multi-bit rate method has been increasingly used as a means for dynamically changing to a mode having a different bit rate. In this multi-bit rate system, the data compression ratio is increased as the bit rate decreases, so that data can be reproduced on the client terminal in the same transfer time. That is, when the data compression ratio is increased, the data thinning ratio is increased.
[0005]
In the mode A, compressed data (compression rate CRa) encoded by lowering the data compression rate in order to improve the quality at the time of data reproduction is stream-distributed at a high bit rate BRa. In mode B, the quality at the time of data reproduction is not as good as in mode A. However, compressed data (compression rate CRb (> CRa)) encoded by increasing the data compression rate so as to have a certain level of quality is reduced to a low bit rate. Stream distribution at a rate BRb (<BRa).
[0006]
On the other hand, in a client terminal receiving a streaming service, data received from a server is temporarily stored in a network fluctuation absorbing buffer (hereinafter, simply referred to as a fluctuation absorbing buffer) in order to absorb delay fluctuations in the network. Perform decoding / playback.
[0007]
[Problems to be solved by the invention]
As described above, it is possible to automatically detect network congestion and change the data transfer bit rate to reduce quality degradation due to congestion. However, when the transfer bit rate is switched, the video and audio output at the client terminal is temporarily stopped until the data distributed in the switched mode is stored in the fluctuation absorbing buffer of the client terminal and can be stably reproduced. There was a problem.
[0008]
That is, when a service is started or a mode is switched, first, a certain amount of data is stored in the fluctuation absorbing buffer, and then the data is encoded and reproduced so that the video / audio can be reproduced stably at first.
[0009]
Therefore, there is a time lag from when the client receives the service start request from the user until the client actually starts the service. For example, assuming that a time (time lag) until a certain amount of data is stored in the fluctuation absorbing buffer is m, the time m is usually several seconds to several tens of seconds. Assuming that the time m is, for example, 10 seconds, the above-mentioned time lag, that is, the time from the start of data transfer by the distribution server to the start of video and audio output at the client terminal is 10 seconds.
[0010]
On the other hand, as shown in FIG. 6, when switching the bit rate, a client terminal receiving data in the high bit rate mode A (bit rate: BRa) detects congestion from the loss rate at the time of reception (time t0), the detection result is notified to the server, and the server switches the transmission stream to the low bit rate mode B (bit rate: BRb).
[0011]
However, at the time this change is made, the network is congested and data can only be sent at a low bit rate BRb. Therefore, it takes a time corresponding to the time lag (for example, m = 10 seconds) as described above to store data in the fluctuation absorbing buffer, and the time (time m) between the time lags of t0 to t2 ′ is temporarily The playback is stopped temporarily, and the quality as a streaming service is reduced.
[0012]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a streaming service distribution rate change method, a stream distribution server, a stream distribution program, and an information recording medium thereof, which can reduce a decrease in reproduction quality when a bit rate is switched. is there.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a storage medium storing at least one of sound data and moving image data, and the data compression rate is increased by lowering the data transfer bit rate. A distribution server for performing a streaming service of the stored data by using a multi-bit rate for transferring the stored data to a client terminal connected via a network, wherein the streaming server changes the delivery rate of the streaming service when streaming the stored data. In the distribution server, the data to be distributed is compressed at a first compression rate CRa, and the compressed data is stream-distributed at a first bit rate BRa. Compressed data compressed at the second compression ratio CRb (> CRa) When switching to a state in which the stream is distributed at a second bit rate BRa (<BRa) lower than the rate BRa, the stream distribution of the compressed data compressed at the first compression rate CRa at the first bit rate BRa is stopped. The distribution target at a third compression rate CRc (> CRb) higher than the second compression rate CRb for stream distribution at a third bit rate BRc (<BRb) lower than the second bit rate BRb. The compressed data of the third compression rate CRc distributed at the second bit rate is stream-distributed at the second bit rate BRb, and a predetermined amount of the compressed data of the third compression rate CRc is accumulated in the data buffer of the client terminal. At the point in time when reproduction becomes possible, the second bit rate BR of the compressed data having the third compression rate CRc After the stream distribution by the third compression is stopped, the stream distribution at the fourth bit rate BRb ′ (where BRb ′ <BRb) of the compressed data obtained by compressing the data to be distributed at the second compression ratio CRb, and the third compression A stream of compressed data having a rate CRc is distributed in parallel with the third bit rate BRc, and a predetermined amount of compressed data distributed at the fourth bit rate BRb ′ is accumulated in a data buffer of the client terminal so that it can be reproduced. At this point, a method is proposed for changing the distribution rate of a streaming service in which compressed data obtained by compressing the data to be distributed at the second compression rate CRb is switched to only stream distribution at the second bit rate BRb.
[0014]
According to the method for changing the distribution rate of the streaming service of the present invention, when the distribution server is streaming the sound data or the moving image data to the client terminal, when the quality of the stream distribution is reduced due to network congestion or the like, The distribution server reduces the bit rate of the stream distribution from the first bit rate BRa to the second bit rate BRb.
[0015]
At this time, the distribution server stops the stream distribution of the compressed data compressed at the first compression rate CRa at the first bit rate BRa, and compresses the data to be distributed at the third compression rate CRc. Stream delivery of the compressed data at the second bit rate BRb is started.
[0016]
Further, when the compressed data of the third compression rate CRc is stored in the data buffer of the client terminal by a predetermined amount and becomes reproducible, the distribution server sets the second compression rate of the third compression rate CRc in the data buffer. The stream distribution at the bit rate BRb is stopped. Then, the distribution server distributes the stream of compressed data obtained by compressing the data to be distributed at the second compression rate CRb at a fourth bit rate BRb ′ and the third bit of the compressed data at the third compression rate CRc. Stream distribution at the rate BRc is performed in parallel.
[0017]
When a predetermined amount of compressed data distributed from the distribution server to the client terminal at the fourth bit rate BRb ′ is accumulated in a data buffer of the client terminal and becomes playable, the distribution server Switching to only stream distribution at the second bit rate BRb of compressed data obtained by compressing data at the second compression rate CRb.
[0018]
Therefore, the time from when the data distribution at the first bit rate BRa is stopped and the data reproduction in the client terminal is stopped to when the data reproduction is started again is shorter than before.
[0019]
That is, the time from when the compressed data of the third compression rate CRc is stored in the client terminal until the stored data becomes reproducible, the compressed data of the second compression rate CRb is stored in the client terminal. It is shorter than the time until it is stored and the stored data can be reproduced.
[0020]
Further, since the stream delivery at the third bit rate BRc and the stream delivery at the fourth bit rate BRb ′ are performed in parallel, the stream delivery at the third bit rate BRc is stopped, and When switching to only stream distribution at the rate BRb, data reproduction in the client terminal is not stopped.
[0021]
According to a second aspect of the present invention, there is provided a stream distribution server that implements the method for changing the distribution rate of the streaming service, comprising means for storing at least one of sound data and moving image data, wherein the client is connected via a network. For a terminal, a stream distribution server that stream-distributes the stored data at a multi-bit rate that transfers data at a higher data compression rate as the data transfer bit rate becomes lower, From a state where compressed data compressed at one compression rate CRa is stream-distributed at a first bit rate BRa, compressed data obtained by compressing the data at a second compression rate CRb (> CRa) higher than the first compression rate CRa To a second bit rate B lower than the first bit rate BRa. a (<BRa), the stream distribution of the compressed data compressed at the first compression rate CRa at the first bit rate BRa is stopped, and the stream is distributed from the second bit rate BRb. Compressed data obtained by compressing the data to be distributed at a third compression rate CRc (> CRb) higher than the second compression rate CRb for stream distribution at a lower third bit rate BRc (<BRb). Means for distributing the stream at the second bit rate BRb, and when a predetermined amount of compressed data of the third compression rate CRc distributed at the second bit rate is accumulated in the data buffer of the client terminal and becomes reproducible, After stopping the stream distribution of the compressed data of the third compression rate CRc at the second bit rate BRb, A stream distribution at a fourth bit rate BRb ′ (where BRb ′ <BRb) of the compressed data obtained by compressing the data to be distributed at the second compression rate CRb, and the second compression of the compressed data at the third compression rate CRc. Means for performing stream distribution at the 3-bit rate BRc in parallel; and, when a predetermined amount of compressed data distributed at the fourth bit rate BRb ′ is accumulated in the data buffer of the client terminal and becomes reproducible, The present invention proposes a stream distribution server including means for switching only the stream distribution of the compressed data obtained by compressing the data to be distributed at the second compression rate CRb at the second bit rate BRb.
[0022]
According to a third aspect of the present invention, a server comprising a computer device has means for storing at least one of sound data and moving image data in order to easily implement the method of changing the distribution rate of the streaming service. The stream distribution of a server comprising a computer device that distributes the stored data at a multi-bit rate for transferring data with a higher data compression rate as the data transfer bit rate is lower, to a client terminal connected via the server. From a state in which compressed data obtained by compressing data to be distributed at a first compression rate CRa is stream-distributed at a first bit rate BRa, the data is transmitted at a higher compression rate than the first compression rate CRa. Compressed at 2 compression ratio CRb (> CRa) When switching to a state in which the compressed data is stream-distributed at a second bit rate BRa (<BRa) lower than the first bit rate BRa, the compression performed at the first compression rate CRa at the first bit rate BRa The data stream distribution is stopped, and the third compression rate CRc (higher than the second compression rate CRb for stream distribution at the third bit rate BRc (<BRb) lower than the second bit rate BRb. > CRb), the compressed data obtained by compressing the data to be distributed is stream-distributed at the second bit rate BRb, and the compressed data of the third compression rate CRc distributed at the second bit rate is transmitted to the client terminal. When a predetermined amount of data is stored in the data buffer and can be reproduced, the pressure of the third compression ratio CRc is reduced. After stopping the stream distribution of the data at the second bit rate BRb, the data to be distributed is compressed at the second compression rate CRb according to the fourth bit rate BRb ′ (where BRb ′ <BRb). Performing in parallel the stream delivery and the stream delivery of the compressed data of the third compression rate CRc at the third bit rate BRc, and the compressed data delivered at the fourth bit rate BRb ' Switching the data to be distributed to a stream only at the second bit rate BRb of compressed data obtained by compressing the data to be distributed at the second compression rate CRb at a point in time when the data is accumulated in a buffer and can be reproduced. Suggest a distribution program.
[0023]
A fourth aspect of the present invention proposes a computer-readable information recording medium on which the stream distribution program according to the third aspect is recorded so that the stream distribution program can be easily distributed.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0025]
FIG. 1 is a configuration diagram illustrating a stream distribution service system according to an embodiment of the present invention, FIG. 2 is a block diagram illustrating a configuration of a distribution server according to an embodiment of the present invention, and FIG. FIG. 3 is a block diagram showing the configuration of FIG.
[0026]
In FIG. 1, reference numeral 1 denotes a distribution server, which packetizes data such as moving images and audio and distributes the data to a client terminal 3 via a network 2 such as the Internet. The client terminal 3 receives the data distributed from the distribution server 1, converts it into video and audio, and outputs it. Reference numeral 4 denotes a connection line connecting the distribution server 1 and the network 2, and reference numeral 5 denotes a distribution stream which is a data flow between the distribution server 1 and the client terminal 3.
[0027]
The distribution server 1 is composed of a well-known computer device in which a predetermined program is installed, and as shown in FIG. 2, a line control unit 11, a communication control unit 12, a database management system unit (hereinafter, referred to as a DB management system unit). 13, a sound database (hereinafter, referred to as a sound DB) 14, and a video database (hereinafter, referred to as a video DB) 15. It should be noted that the video DB 15 stores video-only data and data in which video data and sound data are integrated as video data. Each component of the distribution server 1 is composed of both hardware and software.
[0028]
In the distribution server 1, the line control unit 11 is connected to a DB management system unit 13 via a communication control unit 12, and the DB management system unit 13 is connected to a sound DB 14 and a video DB 21.
[0029]
The client terminal 3 is a well-known computer device on which a predetermined program is installed, and includes a display unit 31, a display control unit 32, a communication control unit 33, a line control unit 34, fluctuation absorbing buffers 35A and 35B, a mouse 36, and a speaker. 37. Each component of the client terminal 3 is composed of both hardware and software.
[0030]
In the client terminal 3, the display unit 31 is connected to the communication control unit 33 via the display control unit 32. The communication control unit 33 is connected to each of the line control unit 34, the fluctuation absorbing buffers 35A and 35B, the mouse 36, and the speaker 37.
[0031]
The line controller 34 of the client terminal 3 is connected to the line controller 11 of the distribution server 1 via the network 2.
[0032]
Next, the operation of the present embodiment having the above-described configuration will be described with reference to FIGS. Here, FIG. 4 is a diagram for explaining data to be stream-distributed, and FIG. 5 is a flowchart for explaining stream distribution processing in the distribution server.
[0033]
A user who wants to distribute data operates the client terminal 3 to connect a network connection between the client terminal 3 and the distribution server 1, and establishes a network connection between the client terminal 3 and the distribution server 1. Is transmitted from the client terminal 3 to the distribution server 1 using a menu request command.
[0034]
Upon receiving the menu request command, the distribution server 1 reads the menu from the sound DB 14 and the video DB 15, edits the menu confirmation response, and transfers the menu confirmation response to the client terminal 3.
[0035]
When the client terminal 3 receives the menu confirmation response, the line control unit 34 notifies the communication control unit 33 of the menu confirmation response. Upon receiving this, the communication control unit 33 displays the menu on the display unit 31 via the display control unit 32.
[0036]
The user operating the client terminal 3 specifies a desired option from the menu displayed on the display unit 31 using the mouse 36. Thereby, a data distribution request is transmitted from the client terminal 3 to the distribution server 1.
[0037]
Upon receiving the distribution request from the client terminal 3, the distribution server 1 packetizes the requested data (data to be distributed) at a first compression rate CRa, packetizes the compressed data, and converts it into a packet at a first bit rate BRa. Stream distribution to the client terminal 3 (S1, S2).
[0038]
At this time, the client terminal 3 accumulates the data received from the distribution server 1 in the fluctuation absorption buffer 35A, encodes the data (decompresses the data) after the accumulated data becomes a reproducible state, and reproduces the data.
[0039]
The distribution server 1 confirms the communication state of the network 2 during the data stream distribution and transfers the data (S3). The communication state may be confirmed by using any of various confirmation methods generally used at present depending on the configuration of the stream distribution system. For example, the distribution server 1 may detect whether or not the communication state is good, or the client terminal 3 may detect whether or not the communication state is good and notify the distribution server 1 of the detection result.
[0040]
As a result of checking the communication state, if the communication state is good, the process of S2 is continued. Further, when the communication state deteriorates, the stream distribution of the compressed data compressed at the first compression rate CRa at the first bit rate BRa is stopped, and the third compression rate CRc (>) is higher than the second compression rate CRb. The compressed data obtained by compressing the data to be distributed in CRb) is stream-distributed at the second bit rate BRb (S4).
[0041]
At this time, the client terminal 3 accumulates the data received from the distribution server 1 in the fluctuation absorption buffer 35A in the same manner as described above, encodes the data (decompresses the data) after the accumulated data is in a reproducible state, To play.
[0042]
The second compression rate CRb is a compression rate higher than the first compression rate CRa, and the data compressed at the second compression rate CRb has the data amount of the data compressed at the first compression rate CRa. Less than the amount of data. Further, by distributing the compressed data compressed at the second compression rate CRb at the second bit rate BRb lower than the first bit rate BRa, the data can be reproduced almost in real time. The third compression rate CRc is a compression rate when a stream is distributed at a third bit rate BRc (<BRb) lower than the second bit rate BRb, and is compressed at the third compression rate CRc. The data amount of the data is smaller than the data amount of the data subjected to the second compression ratio CRab compression. Further, by delivering the compressed data compressed at the third compression rate CRc in a stream at the third bit rate BRc lower than the second bit rate BRb, the data can be reproduced almost in real time.
[0043]
In the present embodiment, the first bit rate BRa is set to 1000 kbps, the second bit rate BRb is set to 500 kbps, and the third bit rate BRc is set to 100 kbps. Note that these set values are merely examples, and each bit rate in the present invention is not limited to these values.
[0044]
Next, the distribution server 1 determines whether or not the compressed data of the third compression rate CRc (> CRb), which is stream-distributed at the second bit rate BRb, has reached a storage amount that can be reproduced by the client terminal 3. A determination is made (S5). This determination may be made by measuring the amount of data transmitted by the distribution server 1, or by receiving a notification from the client terminal 3 that the client terminal 3 has entered a data reproducible state. You may do it.
[0045]
As a result of the determination, when the compressed data of the third compression rate CRc, which is stream-distributed at the second bit rate BRb, reaches a storage amount that can be reproduced in the client terminal 3, the distribution server 1 performs the third compression rate Stopping the stream delivery of the CRc compressed data at the second bit rate BRb, and delivering the compressed data obtained by compressing the delivery target data following the delivered data at the third compression rate CRc at the third bit rate BRc; Stream distribution of the compressed data obtained by compressing the distribution target data at the second compression rate CRb at the fourth bit rate BRb ′ is performed in parallel (S6).
[0046]
Note that the fourth bit rate BRb 'is lower than the second bit rate BRb and higher than the third bit rate BRc. Further, a predetermined amount of data to be compressed at the third compression rate CRc is secured in advance, and data subsequent to this data is compressed at the second compression rate CRb. In the present embodiment, the amount of data compressed at the third compression rate CRc is the amount that can be stream-distributed until the data compressed at the second compression rate CRb is accumulated in the client terminal 3 and becomes reproducible. Is set to
[0047]
When the compressed data of the third compression rate CRc stored in the fluctuation absorbing buffer 35A reaches a reproducible storage amount, the client terminal 3 encodes the data and reproduces the data. Further, the client terminal 3 accumulates the compressed data of the third compression ratio CRc, which is stream-distributed at the third bit rate BRc, in the fluctuation absorbing buffer 35A, and reproduces the data following the data stored in the fluctuation absorbing buffer 35A. I do. Further, the client terminal 3 stores the compressed data of the second compression rate CRb stream-distributed at the fourth bit rate BRb 'in the other fluctuation absorbing buffer 35B, and stores the data stored in the one fluctuation absorbing buffer 35A. When the reproduction of all the data has been completed, the reproduction of the data accumulated in the fluctuation absorbing buffer 35B is started following the data reproduction.
[0048]
Next, the distribution server 1 determines whether or not the compressed data of the second compression ratio CRb, which has been stream-distributed at the fourth bit rate BRb ′, has reached a storage amount that can be reproduced in the client terminal 3 (S7). ). This determination may be made by measuring the amount of data transmitted by the distribution server 1 in the same manner as described above, or the distribution server 1 may be notified from the client terminal 3 that the data can be reproduced. The determination may be made based on the above.
[0049]
As a result of the determination, when the compressed data of the second compression rate CRb, which is stream-distributed at the fourth bit rate BRb ′, has reached a storage amount that can be reproduced in the client terminal 3, the distribution server 1 performs the third compression. The stream distribution of the compressed data of the rate CRc at the third bit rate BRbc and the stream distribution of the compressed data of the second compression rate CRc at the fourth bit rate BRbc ′ are stopped, and the data to be distributed is converted to the second compression rate BRbc. Switching to only the stream distribution of the compressed data compressed by CRb at the second bit rate BRb (S8).
[0050]
Next, the distribution server 1 determines whether or not the communication state of the network 2 has been recovered (S9). When the communication state has been recovered, the distribution server 1 proceeds to the process of S2 and returns the data transfer amount to the normal state. .
[0051]
As described above, in the present embodiment, as shown in FIG. 4, the bit rate switching is performed by changing the first compression ratio CRa in order to improve a temporary service failure state in which video data and sound data cannot be reproduced. Rather than simply switching the transfer of the compressed data at the high bit rate BRa (mode A) to the transfer of the compressed data at the second compression rate CRb at the low bit rate BRb (mode B), the third compression is temporarily performed. A transfer mode (modes C1 and C2) of the compressed data at the rate CRc is created, and the state of stream distribution is changed from mode A [time t0] → mode C1 and C2 [time t2] → mode B. This makes it possible to improve the above-mentioned service unavailable state.
[0052]
That is, the details of the operations in the modes C1 and C2 are as follows. It is the same as the conventional example up to the point of time t0 when the congestion is detected and the transmission stream is determined to be switched.
[0053]
(Mode C1)
The time during which the mode C1 is executed is a time until the client terminal 3 becomes in a data reproducible state, and is at least m × (BRc / BRb). Here, m is the time of the aforementioned time lag. At time t0, instead of switching to the stream delivery of the compressed data of the second compression rate CRb at the second bit rate BRb, the stream of the compressed data of the third compression rate CRc is delivered at the second bit rate BRb. That is, data is transmitted at BRb / BRc double speed.
[0054]
At the time (time t1) when the data is accumulated in the fluctuation absorption buffer 35A and can be reproduced (time t1), the client terminal 3 starts reproducing the data distributed in the mode C1.
[0055]
As described above, by distributing the compressed data of the third compression rate CRc in a stream at the second bit rate BRb, the time required for the compressed data of the third compression rate CRc to be accumulated in the fluctuation absorbing buffer and become a reproducible state is obtained. , BRb >> BRc, it suffices to be BRc / BRb times that of the conventional method of distributing data in mode B from the beginning. That is, the time lag at which data cannot be reproduced is 0.2 times that of the above-described conventional example when the above-mentioned example, that is, when BRa = 1000 kbps, BRb = 500 kbps, and BRc = 100 kbps. The service in the mode C1 does not reach the reproduction quality that can be realized in the mode B, but the service quality is much better than the completely stopped state because some video / audio can be reproduced.
[0056]
(Mode C2)
Since the time during which the mode C2 is performed is the time until the compressed data of the second compression ratio CRb, which is stream-distributed at the fourth bit rate BRb ′, becomes a data reproducible state in the client terminal 3, at least m × BRb / (BRb-BRc).
[0057]
When the data of mode C1 is accumulated in the fluctuation absorbing buffer 35A and becomes reproducible (time t1), the data to be reproduced by the client terminal 3 remains the data compressed at the third compression ratio CRc. The data to be transferred is transferred to a combination of the compressed data of the third compression rate CRc and the compressed data of the second compression rate CRb.
[0058]
However, since the maximum bit rate that can be transmitted from the distribution server 1 to the client terminal 3 is only the second bit rate BRb as a whole, the fourth bit rate BRb ′ is at most BRb−BRc.
[0059]
In the client terminal 3, the compressed data of the second compression ratio CRb is stored in the fluctuation absorption buffer for mode B. At this time, it takes time m × BRb / (BRb−BRc) (time between times t1 and t2) to sufficiently store data in the fluctuation absorption buffer for mode B.
[0060]
(Mode B)
When the mode C2 is completed (time t2), the client terminal 3 is ready to reproduce the compressed data of the second compression rate CRb, so that the distribution server 1 transmits only the compressed data of the second compression rate BRb to the second bit rate BRb. The client terminal 3 also switches the data such as video / audio to be reproduced to the data of the second compression rate BRb, and stream-distributes the compressed data of the second compression rate CRb at the initial target second bit rate BRb. To mode B. The rest is the same as the conventional example.
[0061]
As described above, according to the present embodiment, it is possible to improve the streaming service quality in the network 2 having unstable quality. Where the data reproduction is stopped for the time m in the conventional example, the complete data reproduction stop time is suppressed to m × BRc / BRb in the present embodiment, and the time to be started in the mode B is m × (2BRb −BRc) × BRc / ((BRb−BRc) × BRb) is slower than the conventional example, but if an appropriate parameter that satisfies BRb >> BRc is selected, this value becomes smaller and the improvement effect is larger.
[0062]
Note that the present embodiment is a specific example of the present invention, and it goes without saying that the present invention is not limited to only the above embodiment.
[0063]
Also, by creating and distributing an information recording medium on which the computer program of the above-mentioned distribution server 1 is recorded, or distributing it via a network, the distributed computer program can be easily installed on a computer by simply installing the computer program on the computer. Can be configured.
[0064]
【The invention's effect】
As described above, according to the present invention, when the quality of stream distribution is degraded due to network congestion or the like, the distribution server converts the compressed data of the first compression rate CRa from the stream distribution at the first bit rate BRa to the second bit rate. At the time of moving to the stream distribution of the compressed data of the compression rate CRb at the second bit rate BRb, the stream distribution of the compressed data of the third compression rate CRc at the second bit rate BRb is performed. After the stream distribution of the compressed data of the third compression rate CRc at the third bit rate BRc and the stream distribution of the compressed data of the second compression rate CRb at the fourth bit rate BRb ′ are performed in parallel, the second compression rate Since it is possible to switch only the stream distribution of the CRb compressed data at the second bit rate BRb, Since the time from when the data distribution in the BRa is stopped and the data reproduction in the client terminal is stopped and when the data reproduction is started again is shorter than before, the quality of the stream service can be improved. .
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a stream distribution service system according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a distribution server according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a client terminal according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating data distributed in a stream according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating stream distribution processing in a distribution server according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating data distributed in a stream in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Distribution server, 2 ... Network, 3 ... Client terminal, 4 ... Connection line, 5 ... Distribution stream, 11 ... Line control part, 12 ... Communication control part, 13 ... Database management system part, 14 ... Sound database, 15 ... Image database, 31 display unit, 32 display control unit, 33 communication control unit, 34 line control unit, 35A, 35B fluctuation fluctuation buffer, 36 mouse, 37 speaker.

Claims (4)

Means for storing at least one of sound data and moving image data, and a streaming service of the stored data is provided by using a multi-bit rate for transferring data at a higher data compression rate as the data transfer bit rate becomes lower. A delivery server for performing a delivery rate change method of a streaming service when the stored data is stream-distributed to a client terminal connected via a network,
The distribution server,
From a state where compressed data obtained by compressing data to be distributed at a first compression rate CRa is stream-distributed at a first bit rate BRa, the data is converted to a second compression rate CRb (>) higher than the first compression rate CRa. When switching the compressed data compressed at CRa) to a state of stream distribution at a second bit rate BRa (<BRa) lower than the first bit rate BRa,
Stopping the stream distribution of the compressed data compressed at the first compression rate CRa at the first bit rate BRa,
The data is distributed at a third compression rate CRc (> CRb) higher than the second compression rate CRb for stream distribution at a third bit rate BRc (<BRb) lower than the second bit rate BRb. Streaming the compressed data obtained by compressing the data at the second bit rate BRb,
When a predetermined amount of the compressed data of the third compression rate CRc distributed at the second bit rate is accumulated in the data buffer of the client terminal and becomes reproducible, the compressed data of the third compression rate CRc can be reproduced. After stopping the stream distribution at the 2-bit rate BRb,
A stream distribution at a fourth bit rate BRb ′ (where BRb ′ <BRb) of the compressed data obtained by compressing the data to be distributed at the second compression rate CRb, and the compression of the compressed data at the third compression rate CRc. The stream distribution at the 3-bit rate BRc is performed in parallel,
When a predetermined amount of compressed data distributed at the fourth bit rate BRb ′ is accumulated in the data buffer of the client terminal and becomes reproducible, the compressed data obtained by compressing the data to be distributed at the second compression rate CRb A delivery rate changing method for a streaming service, wherein the method switches to only stream delivery at the second bit rate BRb. Means for storing at least one of sound data and moving image data, and transferring the data to a client terminal connected via a network with a higher data compression ratio as the data transfer bit rate is lower. In a stream distribution server that streams the stored data at a multi-bit rate,
From a state where compressed data obtained by compressing data to be distributed at a first compression rate CRa is stream-distributed at a first bit rate BRa, the data is converted to a second compression rate CRb (>) higher than the first compression rate CRa. CRa), when switching to a state in which the stream is distributed at a second bit rate BRa (<BRa) lower than the first bit rate BRa, the first compression rate based on the first bit rate BRa The stream distribution of the compressed data compressed by CRa is stopped, and the stream is further transmitted to a third bit rate BRc (<BRb) lower than the second bit rate BRb. 3 The compressed data obtained by compressing the data to be distributed at a compression rate CRc (> CRb) is expressed by the second bit rate BRb. And means for stream delivery,
When a predetermined amount of the compressed data of the third compression rate CRc distributed at the second bit rate is accumulated in the data buffer of the client terminal and becomes reproducible, the compressed data of the third compression rate CRc can be reproduced. After stopping the stream distribution at the 2-bit rate BRb, stream distribution at a fourth bit rate BRb ′ (where BRb ′ <BRb) of compressed data obtained by compressing the data to be distributed at the second compression rate CRb; Means for concurrently performing stream distribution of the compressed data having the third compression rate CRc at the third bit rate BRc;
When a predetermined amount of compressed data distributed at the fourth bit rate BRb ′ is accumulated in the data buffer of the client terminal and becomes reproducible, the compressed data obtained by compressing the data to be distributed at the second compression rate CRb Means for switching only to stream delivery at the second bit rate BRb. Means for storing at least one of sound data and moving image data, and transferring the data to a client terminal connected via a network with a higher data compression ratio as the data transfer bit rate is lower. A computer program for performing the stream distribution of a server including a computer device that distributes the stored data at a multi-bit rate,
From a state where compressed data obtained by compressing data to be distributed at a first compression rate CRa is stream-distributed at a first bit rate BRa, the data is converted to a second compression rate CRb (>) higher than the first compression rate CRa. CRa), when switching to a state in which the stream is distributed at a second bit rate BRa (<BRa) lower than the first bit rate BRa, the first compression rate based on the first bit rate BRa The stream distribution of the compressed data compressed by CRa is stopped, and the stream is further transmitted to a third bit rate BRc (<BRb) lower than the second bit rate BRb. 3 The compressed data obtained by compressing the data to be distributed at a compression rate CRc (> CRb) is expressed by the second bit rate BRb. The method comprising the steps of: stream delivery,
When a predetermined amount of the compressed data of the third compression rate CRc distributed at the second bit rate is accumulated in the data buffer of the client terminal and becomes reproducible, the compressed data of the third compression rate CRc can be reproduced. After stopping the stream distribution at the 2-bit rate BRb, stream distribution at a fourth bit rate BRb ′ (where BRb ′ <BRb) of compressed data obtained by compressing the data to be distributed at the second compression rate CRb; Performing, in parallel, stream distribution of the compressed data having the third compression rate CRc at the third bit rate BRc;
When a predetermined amount of compressed data distributed at the fourth bit rate BRb ′ is accumulated in the data buffer of the client terminal and becomes reproducible, the compressed data obtained by compressing the data to be distributed at the second compression rate CRb Switching to stream delivery only at the second bit rate BRb. A computer-readable information recording medium on which the stream distribution program according to claim 3 is recorded.

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