JP2004215074A - Server, transmitting rate control method, program, and record medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To conduct data communication by a bit rate suitable for the network band. <P>SOLUTION: In transmission for video audio data (stream data) constituted with unit data via a network 20, data of different compression rate (amount of data) are prepared beforehand as the candidates of unit data to be transmitted. Unit data are transmitted about the level closest to and below an upper limit of a bit rate determined for a detected band of the network 20 is transmitted. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology for transmitting video and audio data via a network.
[0002]
[Prior art]
There is a system for transmitting data relating to video and audio (hereinafter referred to as video / audio data) from a server to a user terminal via a network such as the Internet. The server, which is the data sender, detects the network bandwidth and adjusts the amount of data to be transmitted (bit rate). Here, as means for adjusting the data amount, (1) a method of changing the data amount by changing the compression rate of the encoding device (encoder), (2) data prepared in advance with a plurality of compression rates is prepared. A method of transmitting any data based on the average amount of encoded data is known (see Non-Patent Document 1).
[0003]
[Non-patent document 1]
Hagino, Onoe, Yasugi, Atsumi, Komaki, Murao, Kushida, Yamauchi, "File Switching Method in Mobile Streaming QoS Server", IEICE, MoMUc 2001-121, pp91-pp98, Mar. 2002
[0004]
[Problems to be solved by the invention]
In the above method (1), it is not possible to know how much the data amount changes until the encoding process is actually completed, and there is a possibility that the data amount may be unnecessarily reduced / increased. For example, as a result of lowering the bit rate more than necessary, there is a problem that the image quality of the reproduced video is rapidly deteriorated in the user terminal receiving the data.
[0005]
On the other hand, according to the method (2), since the encoding process is performed in advance, the above-described problem does not occur. However, in the method (2), when the data amount of the encoded data temporarily increases, data transmission control ignoring the network bandwidth is performed, causing data congestion and packet loss. This has led to a problem that normal video reproduction cannot be performed on the user terminal.
An object of the present invention is to provide a technique for transmitting video and audio data via a network without any problem without causing the above-described problems.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the server according to the present invention compresses video and audio data transmitted via a network at different compression rates, and converts each of the compressed data from the start of reproduction of the video and audio data. A storage unit that divides each other at regular time intervals and stores a bit rate of the divided data generated by the division, a detection unit that detects the band of the network, And a controller that determines a bit rate along the detected band among the bit rates according to the above as a transmission rate.
According to the configuration of the server, the video and audio data transmitted via the network is compressed at different compression ratios, and each of the compressed data is divided from each other at regular intervals from the start of reproduction of the video and audio data, The bit rates of the divided data generated by the division are stored, and among the bit rates related to the divided data at the same playback time of the video and audio data, the bit rate along the detected network band is determined as the transmission rate. Is done. For this reason, data transmission is always performed at a bit rate along the band of the network.
[0007]
In the configuration of the server described above, the storage unit is a management table in which bit rates related to the divided data at the same time of reproduction of the video / audio data are arranged. Is stored, and the control unit determines, as the transmission rate, the bit rate value in the management table that is closest to the bit rate upper limit specified by the detected band on the inner ring. May be characterized. In this case, the contents of the management table are updated in order of the bit rate from low to high at regular time intervals. Therefore, the transmission rate is determined based on the inner band closest to the bit rate upper limit specified by the detected band. This is convenient for the user.
[0008]
The transmission rate control method according to the present invention compresses video and audio data to be transmitted via a network at different compression rates, and divides each of the compressed data at regular intervals from the start of reproduction of the video and audio data. Storing the bit rates of the divided data generated by the division, detecting the network bandwidth, and detecting the bit rate of the divided data at the time when the video / audio data is reproduced. And determining the transmission rate along the determined band as the transmission rate.
By using such a method, data transmission can always be performed at a bit rate along the bandwidth of the network, and there is no possibility that problems such as data congestion and packet loss in the network will occur.
[0009]
The program according to the present invention compresses a server at different compression ratios of video and audio data transmitted via a network, and divides each of the compressed data at regular intervals from the start of reproduction of the video and audio data. Means for respectively storing the bit rates of the divided data generated by the division, means for detecting the band of the network, and detection of the bit rate of the divided data at the same time when the reproduction of the video and audio data is performed. It is characterized in that it functions as means for determining a transmission rate along the determined band as a transmission rate.
If such a program is used, data transmission can always be performed at a bit rate along the bandwidth of the network, and there is no possibility that problems such as data congestion and packet loss in the network will occur.
If the above-mentioned program is recorded on various recording media such as FD (Floppy Disk) and CD-ROM (Compact Disc Read Only Memory), convenience at the time of installing the program and at the time of transaction of the program is achieved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the contents of one embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a data transmission system (hereinafter, simply referred to as a system) 100 to which the present invention is applied. There may be more user terminals 10 than shown in FIG.
The present system 100 is a system for transmitting video / audio data of the user terminal 10 from the server 30 via the network 20. The video and audio data according to the present embodiment is data relating to content such as a movie, for example, and is assumed to be encoded according to the MPEG4 (Moving Picture Experts Group4) standard. The encoding standard may be another standard such as MPEG2 or MP3 (MPEG-1 Audio Layer 3).
[0011]
The user terminal 10 is a mobile phone or the like, and decodes video and audio data transmitted from the server 30 and performs video and audio reproduction processing.
The network 20 is a data communication network such as the Internet. The bandwidth of the network 20 varies according to the number of terminals sharing communication in the network 20.
The server 30 is, for example, a PC (Personal Computer) and has a CPU (Central Processing Unit) and a hard disk (storage unit). In the server 30, programs for encoding processing according to the MPEG4 standard, detecting a band of the network 20, and the like are installed in advance.
[0012]
Next, the operation of the server 30 characterizing the contents of the present embodiment will be described. FIG. 2 is a flowchart showing processing contents when the server 30 prepares various tables for encoding data and managing data as a preparation stage for transmitting video / audio data to the user terminal 10. Hereinafter, description will be given with reference to FIG.
[0013]
(1) Creation of a video file (FIG. 2: Step Sa1)
The server 30 performs compression processing (encoding processing) on one video / audio (content) data at different compression rates (encoding rates), and creates a file (video file) related to the compressed data. The content of the video file is a collection of encoded data based on the MPEG4 standard, for example, frame data of 15 frames per second.
FIG. 3 shows a conceptual diagram of a process of generating a video file. One video / audio data is encoded at an encoding rate R1 to generate a video file F1. Also, the same video / audio data is encoded at another encoding rate R2 to create a video file F2. Other video files are similarly generated.
Each of the video files F1, F2,... Is common in that it contains 15 frames of frame data per unit time (one second), but is encoded at a different encoding rate. The files F1, F2,... Have different compression ratios.
[0014]
(2) Determination of index number etc. (FIG. 2: Step Sa2)
Next, the server 30 performs the thinning-out processing on each of the generated video files F1, F2,... In some predetermined patterns (thinning-out patterns). The thinning process is a process performed for every 15 frame data included per unit time (1 second).
In the present embodiment, for each video file, divided data obtained by dividing every fixed time (1 second) from the start of reproduction of video and audio, that is, divided data divided for every 15 frame data, It will be called "unit data".
[0015]
FIG. 4 shows the concept of focusing on one unit data included in the video file F1 and performing a thinning process on this unit data. Note that the video file F1 shown in FIG. 4 is made up of three types of frame data, i.e., I frame data, P frame data, and B frame data in consideration of a general MPEG format (MPEG1 and MPEG2). When the MPEG4 format is used, only the I frame data and the P frame data are used.
[0016]
FIG. 4 shows two types of thinning patterns (thinning patterns a and b), of which the thinning pattern a leaves frame data (I frame data) located at the head of unit data and thins other frame data. It does the processing.
The thinning pattern “b” is a processing for thinning out other frame data (B frame data) while leaving the I frame data and the P frame data included in the unit data.
[0017]
Such a thinning pattern is determined in advance based on the properties of each frame data. For example, since the I frame has no data dependency from other P frames or B frames, even if the thinning processing (thinning pattern a) is performed so that the I frame data remains, the subsequent reproduction processing can be performed without any problem. Further, since the P frame has data dependency from the I frame (or P frame) in the same unit data, if the thinning processing (thinning pattern b) is performed so as to leave the data of the I frame and the P frame, the subsequent reproduction is performed. Processing can be executed without any problem.
In this way, a thinning pattern based on the data processing after the thinning processing is prepared in advance, and thereby, the thinning processing is performed on the same unit data with a plurality of thinning patterns, and a plurality of new unit data having different data amounts are generated. You do it.
[0018]
As described above, the details of the thinning process have been specifically described by focusing on one unit data of the video file F1, but such a thinning process is performed on all the unit data included in the video file F1.
FIG. 5 schematically shows the contents of the unit data included in the video file F1. Unit data F1-1, F1-2,..., F1-n are shown in order from the unit data located at the head of the video file F1 to the unit data located at the end point. The unit data located at the end of the video file F1 is F1-n. In the present embodiment, the unit data corresponds to data per second. Therefore, n is a natural number indicating the playback time length of video and audio (content). is there.
.., F1-n in such a video file F1 are converted into unit data F1-a1 and F1-a2 by performing thinning-out processing a on each of the unit data F1-1,. ,..., F1-an, and the unit data generated by performing the thinning-out processing b is referred to as unit data F1-b1, F1-b2,.
[0019]
FIG. 6 is a conceptual diagram showing a state where each of the unit data generated in this way is stored in the server 30. Each unit data includes a name (identification number) for specifying the unit data and the data amount of the unit data. In the present embodiment, since the unit data corresponds to data per second, the data amount of each unit data corresponds to the bit rate when transmitting via the network 20.
[0020]
As shown in FIG. 6, the server 30 stores individual unit data in order from the head of the video file to the end point. For this reason, in FIG. 6, if the reproduction (decode) processing is performed in the order of the unit data F1-a1, F1-a2,..., F1-an, one video / audio is reproduced. The unit data F1-a1 and the unit data F1-b1 are different in data amount, that is, the quality of video and audio when reproduced, but have the same contents.
Therefore, even when the reproduction processing is performed in the order of the unit data F1-a1, F1-a2,..., F1-an, the unit data F1-a1 is replaced with the unit data F1-b1, and the unit data F1-a1 is replaced. Even when the reproduction processing is performed in the order of b1, F1-a2,..., F1-an, the quality of the obtained video and audio is different, but the content is the same.
[0021]
In the above, the contents when the thinning processing is performed on the video file F1 with the thinning patterns a, b,... Have been described, but the video files F2, F3,. , Respectively, the thinning patterns a, b,... Then, the server 30 stores the generated unit data in the order from the beginning to the end point of the video file as shown in FIG.
In FIG. 6, each unit data corresponds to one second of data of video and audio (content), and is the same in that it is stored in order of time from the start of the content. For this reason, in FIG. 6, although the unit data F1-a1, F1-b2,..., F2-a1, F2-b1,. The content (video) obtained by the above is almost the same.
[0022]
After storing the individual unit data in this way, the server 30 unit data groups (for example, unit data F1-a1, F1-a2,..., F1- The average value of the bit rate is calculated for each data group (an data group). Then, index numbers are assigned in ascending order of the average value of the bit rates (see FIG. 6).
[0023]
(3) Creation of management table (FIG. 2: step Sa3)
Thereafter, the server 30 sorts in ascending order of the index numbers, that is, in ascending order of the average bit rate, and creates a management table. FIG. 7 illustrates the contents of the management table. In a conventional data transmission system, bit rate control during data transmission is performed based on the value of the average bit rate. For this reason, it is not possible to detect a phenomenon in which the bit rate temporarily changes to a large or small value, and various problems (data congestion, packet loss, etc.) in the network 20 occur as described above. .
[0024]
(4) Creation of a dynamic management table (FIG. 2: Step Sa4)
Next, the server 30 generates a dynamic management table which is a feature of the present embodiment. The dynamic management table is a table generated (updated) every unit time (1 second in the present embodiment) from the start of transmission of video and audio data (corresponding to the start of reproduction of video and audio data).
[0025]
FIG. 8 shows the dynamic management at the 0th second from the start of the content and at the 1 second elapse when the reproduction start time of the video / audio data (corresponding to the transmission start time when transmitting the video / audio data) is set to 0 second. It shows the contents of the table.
Here, the dynamic management table at the 0th second contains unit data (unit data F1-a1, F1-b1,..., F2-a1, F2-b1,. ) Are sorted in ascending order of bit rate. Further, the dynamic management table after one second has elapsed includes unit data (unit data F1-a1, F1-b1,..., F2-a1, F2-b1 in FIG. 6) corresponding to one to two seconds from the start of the content. ,...) Are rearranged in ascending order of bit rate.
[0026]
As shown in FIG. 8, the order of arrangement of the dynamic management tables is irrelevant to the index number, that is, the order of the average bit rate, and is arranged in ascending order of the bit rate of the unit data at that time. For this reason, even if the bit rate of a certain unit data temporarily becomes high / low, the content is faithfully reflected in the dynamic management table.
The above is the description of the content of the flowchart in FIG.
[0027]
The server 30 transmits the video / audio data to the user terminal 10 based on the contents of the dynamic management table generated as described above.
FIG. 9 is a flowchart showing the contents of the operation when the server 30 transmits the video / audio data.
When starting transmission of video and audio data to the user terminal 10, the server 30 first detects the band of the network 20 and determines the upper limit of the bit rate (step Sb1). A program for detecting the band of the network 20 and determining the upper limit of the bit rate is installed in the server 30 in advance.
[0028]
Next, the server 30 generates a dynamic management table at the time (here, the reproduction start time of the video / audio data) (step Sb2). The dynamic management table at this time corresponds to a table in which unit data at the time of starting reproduction of video and audio data are arranged in ascending order of data amount (bit rate value). The server 30 determines the unit data of the bit rate closest to the determined bit rate upper limit value on the inner ring from the contents of the dynamic management table, and determines it as transmission data (step Sb3).
[0029]
This will be described using the dynamic management table illustrated in FIG. The left table in FIG. 8 is a dynamic management table at the start of video / audio data reproduction (at the start of data transmission). Assuming that the upper limit of the bit rate of the network 20 is 27000 (bps), the server 30 determines the unit data F1-b1 of the index number 003 which is the closest to the inner ring of 27000 (bps) as the transmission data. After that, the server 30 actually transmits the transmission data determined in this way to the user terminal 10 (FIG. 9: step Sb4).
[0030]
The above is the operation of the server 30 when the reproduction of the video / audio data is disclosed (at the start of the data transmission). After that, the server 30 detects the band of the network 20 every predetermined time (one second) ( Step Sb1). Then, the contents of the dynamic management table are generated (updated) (step Sb2). For example, if it is one second after the start of the transmission of the video and audio data, the server 30 rearranges the data amount (bit rate value) in ascending order of the unit data at the lapse of one second from the start of the reproduction of the video and audio data. To update the contents of the dynamic management table. The subsequent processing is the same, and the server 30 determines the unit data of the bit rate closest to the determined bit rate upper limit value on the inner ring from the contents of the updated dynamic management table, and determines it as transmission data (step Sb3). And it transmits to the user terminal 10 (step Sb4).
[0031]
This will be described using the dynamic management table illustrated in FIG. The table on the right side in FIG. 8 is a dynamic management table after a lapse of one second from the start of video / audio data reproduction (one second after the start of data transmission). Here, assuming that the upper limit of the bit rate of the network 20 is 27000 (bps), the server 30 determines the unit data F2-a2 of the index number 002 closest to the inner ring of 27000 (bps) as the transmission data. Will do.
[0032]
After that, the server 30 repeats the same control and transmits video and audio data. Every second, the contents of the dynamic management table are updated, and the unit data is rearranged in ascending order of the data rate. Therefore, the unit data closest to the upper limit of the bit rate of the network 20 on the inner ring can be quickly found.
[0033]
As described above, according to the present embodiment, when transmitting video / audio data (stream data) composed of unit data via the network 20, the compression rate (data amount) ) Are prepared in advance. Then, the unit data closest to the inner ring is transmitted with respect to the upper limit of the bit rate determined by detecting the band of the network 20. Therefore, data communication via the network 20 is always performed normally, which is a problem in the related art. However, problems such as data congestion and packet loss do not occur.
[0034]
The contents of each embodiment described above are merely examples, and can be arbitrarily modified. Some of the modifications will be described below.
As long as the information on the data amount (bit rate) of each unit data is stored in the server 30, the effect of the present invention that the unit data suitable for the band of the network 20 is transmitted can be obtained. . For this reason, the unit data itself may be stored in the server 30 and read out as needed to perform data transmission, or the unit data itself may be generated at any time during data transmission without being stored in the server 30. Good.
[0035]
The method of installing the program according to the present invention is optional. In the above embodiment, it is assumed that the program is installed in the server 30 in advance. However, the program may be installed in the server 30 via a storage medium (a floppy disk, a CD-ROM, or the like) storing the contents of the program. In addition, a form using so-called net distribution that is installed via the network 20 or another network may be used.
[0036]
【The invention's effect】
As described above, according to the present invention, transmission of video and audio data according to a network band can be performed without any problem.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a data transmission system 100 according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a procedure in which a server 30 of the data transmission system 100 creates various tables.
FIG. 3 is a conceptual diagram showing a process of creating a video file by the server 30.
FIG. 4 is a conceptual diagram showing the contents of a thinning process performed by the server.
FIG. 5 is a diagram for explaining the contents of a video file created by the server 30.
FIG. 6 is a conceptual diagram showing a state in which unit data is stored in the server 30.
FIG. 7 is a diagram showing contents of a management table stored in the server 30.
FIG. 8 is a diagram showing contents of a dynamic management table stored in the server 30.
FIG. 9 is a flowchart showing the operation of the server 30.
[Explanation of symbols]
10 user terminal, 20 network
30 ... server, 100 ... data transmission system.

Claims (5)

The video and audio data transmitted via the network is compressed at different compression ratios, and each of the compressed data is divided from each other at regular intervals from the start of reproduction of the video and audio data, and the divided data generated by the division A storage unit for storing the bit rate of
A detection unit that detects a band of the network,
A server comprising: a control unit that determines, as a transmission rate, a bit rate along a detected band among bit rates related to the divided data having the same reproduction progress time of the video / audio data. The server according to claim 1,
The storage unit is a management table in which bit rates related to the same divided data at the time of reproduction of the video / audio data are arranged. Remember,
The server, wherein the control unit determines, as a transmission rate, a bit rate value closest to the bit rate upper limit value specified by the detected band among the bit rate values in the management table. The video and audio data transmitted via the network is compressed at different compression ratios, and each of the compressed data is divided from each other at regular intervals from the start of reproduction of the video and audio data, and the divided data generated by the division Storing each of the bit rates of
Detecting the bandwidth of the network;
Deciding, as a transmission rate, a bit rate along the detected band among bit rates related to the divided data having the same reproduction time of the video and audio data. Server
The video and audio data transmitted via the network is compressed at different compression ratios, and each of the compressed data is divided from each other at regular intervals from the start of reproduction of the video and audio data, and the divided data generated by the division Means for storing the respective bit rates of
Means for detecting the bandwidth of the network;
A program that functions as means for determining, as a transmission rate, a bit rate along a detected band among bit rates related to divided data having the same reproduction time of the video and audio data. A recording medium on which the program according to claim 4 is recorded.

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