JPH10308914A - Video server - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video server by which video audio data are distributed to a client at a speed similar to that in a forward reproduction even in the case of reverse reproduction. SOLUTION: In the case of forward reproduction, each block of video audio data consisting of a plurality of frames is reproduced in a forward direction and sequentially written in storage sections IB1 -IBN. In the case of reverse reproduction, each block is reproduced in an opposite sequence to that of the forward reproduction and written sequentially in the storage sections IB1 -IBN, but frames in each block are arranged in the forward direction. A data exchange section DX shares video audio data stored in each storage section to buffer sections OB1 -OBN corresponding to clients. Each buffer section uses address control sections CON1 -CONN to write/read video audio data in the unit of blocks but in the case of reverse reproduction, the frames of each block are read in the reverse sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video server that distributes video and audio data in response to a request from a client.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the configuration of a conventional video server. The video server is a device that distributes video and audio data reproduced from a recording medium such as a CD-ROM in response to a request from a client. In the figure, storage units IB _{1 to} IB _N are means for temporarily storing and outputting video and audio data to be supplied to each client. Temporary buffers TB _{1 to} TB _M are buffers provided for each client, store video / audio data to be delivered to the client, and direct the stored video / audio data to the client at a constant rate. To send. The data exchange unit DX includes storage units IB ₁ to
A means for supplying the temporary buffer corresponding to the client is the respective destination of each video and audio data output from the IB _N.

[0003] In this video server, a plurality of storage units are provided in order to satisfy a demand regarding throughput. That is, it is as follows. First, as shown in the example of FIG. 3, there are M client terminals, and if it is assumed that uncompressed video / audio data of 100 Mbps is distributed to each client, the throughput required of the video server is 100 × It becomes M. Therefore, assuming that only one storage unit is provided, 10
It is necessary to write and read the video and audio data in the storage unit at a speed corresponding to the throughput of 0 × M. However, at present, there is no storage device capable of writing and reading at such a high speed. Therefore, in the video server shown in FIG. 3, provided with a plurality of storage portions IB ₁ ~IB _N, it is the by causing them to multiple simultaneous operation to obtain a throughput of 100 × M. That is, the read speed of one storage unit is LM
In the case of bps, the number N of storage units is selected so that L × N = 100 × M, and the storage units corresponding to the throughput of 100 × M as a whole are constituted by the N storage units. .

[0004] Each video / audio data to be distributed to each client is distributed and stored in a plurality of such storage units. The data exchange unit DX selects the output of the storage unit for each client according to the distribution schedule illustrated in FIG. 4, and transfers the frames of the video and audio data output from each storage unit to the temporary buffer corresponding to the client. Is output to In the example shown in FIG. 4, for example, focusing on the client 1 (output 1), the storage unit I
B ₁ → IB ₂ → IB ₃ → IB ₄ → IB ₁ → ...
The four storage units are cyclically selected by the data exchange unit DX, and the frames # 1, # 2, # 3,
# 4, ... are sequentially supplied to the temporary buffer TB ₁ corresponding to the client 1. Each of these frames is stored in advance in each storage unit prior to reading by the data exchange DX. The same applies to other clients.

[0005] Each frame output from the data exchange unit DX, by through the temporary buffer TB ₁ ~TB _M, is output at a rate that matches the data reading speed of the client. By making the reading speed of the temporary buffer variable, special reproduction such as slow and pause can be performed. In addition, as shown in FIG. 5, by skipping and extracting a frame from the storage unit, it is possible to perform fast forward at a specific double speed.

[0006]

The above-described conventional video server is suitable for reading and delivering video and audio data in the forward direction, but when reading and delivering in the reverse direction, FIG. As shown in the figure, useless empty reading increases in the reading operation, and it is barely possible in the case of slow reproduction, but there is a problem that it is not possible to cope with normal reverse reproduction or rewinding. This is for the following reason.

First, uncompressed video / audio data is stored in the storage unit. This data must be generated from compressed data reproduced from a recording medium. This compressed data consists of data corresponding to each frame of the moving image,
Since the compressed data of each frame is coded by inter-frame predictive coding, it can restore uncompressed video and audio data by itself, and the compressed data and uncompressed video and audio of the preceding frame Uncompressed video and audio data cannot be restored without data or uncompressed video and audio data of the preceding and succeeding frames.

[0008] The compressed data of each of these frames is recorded on the recording medium in an arrangement order such that when read in the forward direction, the compressed data can be efficiently returned to uncompressed data. Therefore, this does not cause any problem when the video and audio data of each frame is reproduced in the forward direction.

[0009] However, when reproducing video and audio data in the reverse direction, compressed data of many frames must be read from a recording medium to reproduce video and audio data for one frame. For this reason, when continuously reproducing uncompressed video / audio data in the reverse direction,
The time interval during which the video and audio data of each frame is reproduced is inevitably lengthened.

[0010] The present invention has been made in view of the circumstances described above, and even when the content is reproduced and distributed in the reverse direction,
It is an object of the present invention to provide a video server capable of reproducing video and audio data at the same speed as in the forward direction and delivering the data to a client.

[0011]

The invention according to claim 1 is
For a plurality of clients, in a video server that delivers video and audio data in response to a request from each, a storage unit for temporarily storing and outputting the video and audio data, and in response to a request from each of the plurality of clients, Means for storing the video and audio data in the storage means, wherein when forward reproduction is requested, a plurality of blocks each composed of video and audio data for a plurality of frames are arranged in an order corresponding to forward reproduction. When the backward reproduction is requested, only the order of each block is reversed while the order of the video / audio data in the block corresponds to the forward reproduction. Input means corresponding to the direction reproduction and stored in the storage means; and input means provided for each of the plurality of clients, each of the clients being A plurality of buffer units for storing video and audio data to be supplied to the client, a data exchange unit for supplying the video and audio data output from the storage unit to the buffer units corresponding to the clients to which each is delivered, Provided in correspondence with the plurality of buffer units, and sequentially writes the video and audio data supplied from the data exchange to the buffer unit to the buffer unit in units of the block, and when forward reproduction is requested, The video / audio data of each frame belonging to each block written in the buffer unit is read out in the same order in which they were written, and if reverse playback is requested, each block written in the buffer unit A plurality of addresses for controlling the reading of the video and audio data of each frame belonging to The video server, characterized by comprising a control unit and gist.

[0012] According to a second aspect of the present invention, the storage means includes:
The input unit sequentially selects the plurality of storage units, sequentially stores video and audio data blocks for the same client, and the data exchange unit includes the plurality of storage units that can operate simultaneously. The video server according to claim 1, wherein the video / audio data for each client, which is distributed and stored in the storage unit, is supplied to a buffer unit corresponding to each client.

The invention according to claim 3 is characterized in that a temporary buffer for adjusting the transmission speed of the video and audio data is arranged at a subsequent stage of the buffer section.
Alternatively, the gist is the video server described in 2.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a video server according to an embodiment of the present invention.
In this video server, each temporary buffer T
B ₁ with ~TB buffer OB ₁ ~OB _M in front of _M is placed, the address control section C for performing each of the write control and read control for these respective buffer
ON _{1 to} CON _M are provided.

Next, the operation of this embodiment will be described.
Focusing on the audiovisual data to be distributed to a client, the video-audio data is stored distributed and divided into a predetermined amount of data in each storage section IB ₁ ~IB _N. In more detail, first, the first data storage unit IB _1, the next data accumulation section IB _2, ..., to the N-th data storage unit IB _N, and, N + 1 th data storage unit IB
_First , each storage section is cyclically selected, and so on, and a series of data is sequentially written. Therefore, even when reading the video and audio data, and to select each storage section IB ₁ ~IB _N cyclically.

The distributed storage of the video and audio data in this order is called striping. In the present embodiment, uncompressed video / audio data is handled, and one frame of video / audio data is used as a striping unit. Therefore, assuming that using consecutive numbers to the video audio data (frames) which are sequentially stored in each storage unit, when the first frame # 1 is stored in the storage unit IB ₁ the accumulation section I
The _Nth frame #N is stored in B _N. Also, in this case, if the remainder obtained by dividing the number of a certain frame by N is H, that frame is stored in the storage unit I
B _H will be stored.

An input unit (not shown) reads compressed data from a recording medium in block units consisting of a plurality of frames in response to a request from a client. This compressed data is coded by the inter-frame prediction coding method. At the input unit, the compressed data is read out in block units and returned to uncompressed video / audio data in response to a request from each client. is, video and audio data thus obtained are sequentially stored in the storage unit IB ₁ ~IB _N frame by frame.

The reproduction mode of each block differs depending on the request from the client. That is, when an instruction to perform forward reproduction of certain video / audio data is given, the input unit sequentially reads out the respective blocks of the relevant video / audio data (compressed data), and performs uncompression corresponding to each block. The video and audio data in the format is played back in the order according to the original playback order of each video (forward playback order corresponding to the passage of time). In this case, the uncompressed video / audio data of each frame in each block is also reproduced in the forward direction. Each block of the video and audio data in uncompressed form in this way is forward reproduction is sequentially written in the storage unit IB ₁ ~IB _N. On the other hand, if an instruction to perform reverse playback of certain video / audio data is given, the input unit places each block of the corresponding non-compressed video / audio data in an order reverse to the original playback order (time lapse and (Reverse order). However, in each block, the uncompressed video / audio data of each frame is reproduced in the forward direction. As described above, each block is reproduced in the backward direction. However, since each frame is reproduced in the forward direction within each block, the time interval for reproducing the video and audio data of each frame is not prolonged. Each block of the video and audio data of such reverse reproduction is uncompressed format has been also sequentially written in the storage unit IB ₁ ~IB _N.

Video / audio data for each client is sequentially output from each of the storage units IB _{1 to} IB _N. That is,
For example, when focusing on the storage unit IB _1, the storage unit the client M from IB _1, client M-1, ..., Client 1, Client M, ... so on, video and audio data is sequentially and the cyclically for each client Is output. Then, the storage unit IB _2, video and audio data for each client is output with a delay period corresponding to one frame than the storage portion IB _1.

The data exchange unit DX includes the storage units IB ₁ -I
Captures video and audio data output from the B _N, the video and audio data for the client 1 to the buffer unit OB _1,
Buffer OB for video and audio data for client 2
To _2, ..., and supplies the video and audio data for the client M to the buffer unit OB _M.

[0021] In the buffer OB ₁ ~OB _M, under control of the address control unit CON ₁ ~CON _M, writing and reading of video and audio data of each frame in the block is performed. That is, the video / audio data of each frame supplied from the data exchange unit DX is sequentially written to each buffer unit. Then, in the buffer unit storing the video / audio data to be played back in the forward direction, the video / audio data of each frame is read out in the forward direction in each block, but the buffer storing the video / audio data to be played back in the backward direction is stored. The section reads the video and audio data of each frame in each block in the reverse direction. Each audiovisual data read from the buffer unit OB ₁ ~OB _M is transmitted via a temporary buffer TB ₁ ~TB _M to each client.

FIG. 2 shows a specific example of the operation of the present embodiment described above. In this figure, for simplicity of explanation exemplifies the case of using the four storage portion IB ₁ ~IB _4. In this example, client 1 has frame #
Requesting reverse playback at normal speed from
Is normal reproduction from frame # 6, client 3 performs normal reproduction from frame # 11, and client 4 performs normal reproduction from frame # 16.

In the figure showing the output contents of each storage unit,
Client There are polygonal line with arrow designated "buffer type" becomes notation, each frame aligned along the polygonal line, which is output from the accumulation unit is supplied to the buffer unit OB ₁ by the data exchange unit DX This is a frame for one.

[0024] These frames are written to the buffer unit OB ₁ in block units in which the four frames as one block, is read from the buffer unit OB _1. That is, in FIG. 2, "read cycle" a period marked, the frame # 16 has already been accumulated from the buffer unit OB _1, # 15, # 14, # 13 are sequentially read. On the other hand, in parallel with this, the buffer unit OB ₁ stores 4 frames of video / audio data to be read in the next read cycle, ie, frame #.
The respective video and audio data of # 9, # 10, # 11 and # 12 are sequentially written. Then, at the next read cycle, in the reverse order audiovisual data for each frame in the buffer unit OB ₁ is the time of writing, i.e., frames # 1
2, # 11, # 10, and # 9 are read in this order. Also, during this time, the next frame to be read during a read cycle # 5, # 6, # 7, audiovisual data # 8 are sequentially written into the buffer unit OB _1. By repeating such an operation, the video / audio data of each frame is sent to the client 1 in the reverse order of the recording.

In this way, in response to the instruction of the backward reproduction, the process of returning the video / audio data to the non-compressed format is performed in the backward direction on a block basis, and each frame belonging to each block is replaced by the buffer unit. Therefore, continuous reverse reproduction can be performed at the same speed as in the case of forward reproduction. In a similar manner, rewinding can be performed by writing video / audio data to the buffer unit in the order of fast-forward data and reading out the data in the reverse order of the writing.

[0026]

As described above, according to the present invention, even in the case of reproducing and distributing in the reverse direction, the video and audio data can be reproduced at the same speed as in the case of the forward direction and distributed to the client. There is an effect that can be.

[Brief description of the drawings]

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

FIG. 2 is a time chart showing the operation of the embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional video server.

FIG. 4 is a time chart showing the operation of the video server.

FIG. 5 is a time chart showing the operation of the video server.

FIG. 6 is a time chart showing the operation of the video server.

[Explanation of symbols]

IB _{1 to} IB _N storage unit DX data exchange unit OB _{1 to} OB _M buffer unit CON _{1 to} CON _M address control unit TB _{1 to} TB _M temporary buffer

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 7/173

Claims (3)

[Claims] 1. A video server that distributes video and audio data to a plurality of clients in response to requests from each of the plurality of clients, comprising: a storage unit that temporarily stores and outputs the video and audio data; A means for storing the video and audio data in the storage means in response to a request, wherein when forward reproduction is requested, a plurality of blocks each composed of a plurality of frames of video and audio data are forward reproduced. Stored in the storage means in a corresponding order, and when the backward reproduction is requested, the plurality of blocks are stored in the respective blocks while keeping the order of the video / audio data in the block corresponding to the forward reproduction. Input means for storing only in the order corresponding to reverse playback and storing in the accumulating means; provided for each of the plurality of clients; A plurality of buffer units each accumulating video / audio data to be supplied to the client; and a data exchange unit for supplying the video / audio data output from the storage unit to the buffer unit corresponding to the client to which each of the distribution destinations is provided. , When video / audio data supplied to the buffer unit from the data exchange is sequentially written to the buffer unit in block units, and forward reproduction is requested. The video and audio data of each frame belonging to each block written in the buffer unit is read out in the same order in which they were written, and when reverse playback is requested, the data is written in the buffer unit. Control is performed to read the video and audio data of each frame belonging to each block in the reverse order in which they were written. Video server, characterized by comprising a plurality of address controller. 2. The storage unit includes a plurality of storage units that can operate simultaneously, and the input unit sequentially selects the plurality of storage units and sequentially stores blocks of video and audio data for the same client. 2. The video server according to claim 1, wherein the data exchange unit supplies the video / audio data for each client, which is distributed and stored in the plurality of storage units, to a buffer unit corresponding to each client. . 3. The video server according to claim 1, wherein a temporary buffer for adjusting a transmission speed of the video and audio data is arranged at a subsequent stage of the buffer unit.