JPH089335A - Multi-channel video playback device - Google Patents

Abstract

(57) [Summary] [Purpose] In a video-on-demand system, a video signal can be supplied to a user immediately after a reproduction request from the user. [Structure] Head blocks of a plurality of compressed video signals held on m disks 2 are supplied to a RAM 5 via a controller 3, a buffer 4 and a multiplexer 6. A plurality of compressed video signals from the disk 2 are time-divided by the multiplexer 6, and the video signals are supplied to the channel requested to be reproduced through the decoder 7, the D / A conversion circuit 8 and the output terminal 9. At this time, the reproduction request signal from the user is supplied from the input terminal 13 to the CPU 14,
14 to controller 3, timing control circuit 15, 1
A control signal is supplied to 6 and a video signal can be provided to the user without interruption. In addition, the compressed video signal from the input terminal 12 is transferred to the network interface 11,
Disk 2 via buffer 10 and multiplexer 6
Supplied to and retained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel video reproducing apparatus capable of immediately reproducing a video signal when a video reproducing request is received from the user and providing the video signal to the user in a video-on-demand system. .

[0002]

2. Description of the Related Art Here, FIG.
Video-on-demand system that receives video playback requests
It is a block diagram showing an example of a system. Video playback indicated by 1
The device has a monitor 41₁~ 41_nAnd its monitor 41
₁~ 41_n42 corresponding to ₁~ 42_nIs connected
There is. The video playback device 1 holds a plurality of video signals.
ing. Terminal 42₁To video playback device 1
If a request is made, the video reproducing device 1 to monitor 41₁
The required video signal is supplied to and is projected.

FIG. 10 is a block diagram showing an example of a detailed inside of the video reproducing apparatus 1. Video signals compressed by encoding are held on m disks (magnetic disks, optical disks, etc.) indicated by 2. From the input terminal 13 to which the terminal is connected, the CPU (Central Processing
Unit) 14 is supplied with a reproduction request signal of a predetermined video signal. The read signal is supplied to the controllers 3 _{1 to} 3 _m corresponding to the supplied reproduction request signal, and the disc 2
_The held compressed video signal is read from _{1 to} 2 _m .

This compressed video signal is an MPEG2 (Moving
Encoding by Picture image coding Experts Group phase 2) is applied to the video signal. Disc 2 ₁
The compressed video signal read from ~ 2 _m is stored in the buffer 4 ₁
It is supplied to the to 4 _m, in the buffer 4 ₁ to 4 _m, with signals supplied from the timing control circuit 15, is read out by the multiplexer 6.

The compressed video signal read by the multiplexer 6 for output from the input terminal 13 to the output terminals 9 _{1 to} 9 _n where the reproduction request signal is generated corresponds to the corresponding decoder 7.
_{1 to} 7 _n . In the decoders 7 _{1 to} 7 _n , the supplied compressed video signal is decoded, and the timing control circuit 1
From the decoders 7 _{1 to} 7 _n after the signal is supplied from D.
The video signal is supplied to the / A conversion circuits 8 ₁ to 8 _n . D /
The video signals converted into analog in the A conversion circuits 8 ₁ to 8 _n are supplied to the user through the output terminals 9 _{1 to} 9 _n as predetermined video signals corresponding to the reproduction request.

Here, in order to correspond to m disks 2, m controllers 3 and m buffers 4 are provided. Further, in order to correspond to n output terminals, n decoders 7 and n D / A conversion circuits 8 are provided. That is, the video reproduction device 1 is an example of a video-on-demand system capable of providing a plurality of compressed video signals to a plurality (n) of users.

Further, the number of channels of the video reproducing apparatus 1 is n [ch], and the decoding speed of the compressed video signal is E.
[Mbps], E × n
A throughput of [Mbps] or more is required. Assuming that the effective data transfer rate of one disk is D [Mbps], if there are E × n / D (= m) disks, the throughput required as a whole is satisfied. However, to supply different video to all output channels,
It is necessary to divide the encoded data of the program into m discs, and to be able to take out the compressed video signal of n channels per unit time.
That is, the compressed video signal for one channel per unit time taken out from one disc is D / n [Mbit]
Then, the product of the number of disks and this corresponds to the compressed video signal for one channel, and the formula (1) is established.

D / n [Mbit] × En / D = E [Mbps] (1)

By the way, generally, in a disc, data is written in concentric circular tracks. In order to increase this data transfer rate, it is necessary to minimize seek and rotation waiting time. In particular, when a large amount of data continues without interruption like a video signal, writing data to continuous tracks and reading them continuously is one method for efficiently transferring data. Therefore, in the configuration shown in FIG. 10, reads data from a disk in a burst, according to the decoder 7 _1-7 decoder 7 put a buffer to the input side of the _{n 1-7 n} decoding speed, the data Will be sent out.

Here, FIG. 11 is a block diagram showing the part of the multiplexer 6 more specifically. The bus slots 51 _{1 to} 51 _m are channels 9 ₁ to which the reproduction request for the compressed video signals read from the disks 2 ₁ to 2 _m is made.
It is output to 9 _n . In addition, the compressed video signal supplied from the input terminal 12 is the network interface 11,
Via a buffer 10, supplied to the bus slot 52 ₁ to 52 _m. In the bus slots 52 _{1 to} 52 _m , the supplied compressed video signal is divided into predetermined blocks, which are supplied to a predetermined disk for recording. These buses slots, by CPU 14, is controlled, predetermined disk 2 ₁ to 2 _m, and channel 9 ₁ to 9 _n corresponding bus slot _{51 1 ~51 m, 52 1 ~52} m is turned on, compressed video Signal is supplied.

By substituting numerical values, the decoding speed E is 6 [Mbps] and the number of channels n is 20 [c].
h] and the effective data transfer rate D is 20 [Mbps], 6 disks are required from the calculation of E × n / D. In order to output a throughput of E × n = 120 [Mbps] during reproduction, the buffer 4 to the decoder 7
The bus 51 to the bus is 120 if the bus width is 8 bits.
[Mbps] × 8 [bit] = 15 [MHz], and compressed video signals are sequentially transferred from channel 1 to channel 20.

At this time, the compressed video signal for one channel is 8 [bit] × 6 [units] = 48 [bit].
In other words, the data transfer cycle of each channel is 6 units.
Since it rotates every × 20 [ch] / 15 [MHz] = 8 [μsec], when the compressed video signal is output, it can be instantaneously supplied to the decoder. Further, the compressed video signal is supplied to the disk via the network interface 11 and m buses 52 having the same function as the bus 51.

[0013]

If the amount of data read from one disk at a time is K [Mbit], the read cycle of each channel at n [ch] is K / D × n [ Seconds]. In other words, in the video on demand system, for all channels
Considering fair service, there is a problem that a maximum of K / D × n [seconds] must be waited until a video data is read from a disc after a reproduction request from a channel.

[0014]

According to the present invention, there is provided a video-on-demand system having a RAM arranged in parallel with a disk holding a plurality of compressed video signals,
A multi-channel video signal device characterized in that the head data blocks of a plurality of compressed video signals held on a disk are stored in a RAM.

Further, according to the present invention, in a video-on-demand system, a FLASH memory arranged in parallel with a disk holding a plurality of compressed video signals is provided, and the heads of the plurality of compressed video signals held on the disk are provided. Is a multi-channel video signal device characterized in that the data block of (1) is stored in a FLASH memory.

[0016]

A video signal compressed by encoding is supplied, and the supplied compressed video signal is divided into a plurality of compressed video files. The first block of the compressed video file divided into a plurality of pieces is arranged in parallel with the disk R
By storing in AM (Random Access Memory),
As soon as the user requests the reproduction of the video signal, RA is immediately issued.
By transferring the first block stored in M, the video signal can be provided to the user without waiting time.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a multi-channel video reproducing apparatus of the present invention. Read magnetic disk for holding the compressed video signal, the disc 2 ₁ to 2 _m, such as an optical disc, the controller 3 ₁ to 3 _m for reading the compressed video signals from the disc 2 ₁ to 2 _m, from the disc 2 ₁ to 2 _m buffer 4 ₁ to 4 _m for adjusting the transfer rate of the compressed video signal compressed video signal and a multiplexer, the first block of the compressed video signal from the disk 2 ₁ to 2 _m, that is, the first block is written to, the multiplexer 6 R to supply compressed video files to
It is composed of an AM 5 and a CPU 14 which controls these.

At this time, the compressed video signals held in the disks 2 ₁ to 2 _m are supplied from the input terminal 12 and supplied to the multiplexer 6 via the network interface 11 and the buffer 10. In the multiplexer 6,
The supplied compressed video signal is divided into multiple blocks,
It is held on a predetermined disk 2 _{1 to} 2 _m . Then, the output terminals 9 _{1 to} 9 _n and the output terminals 9 ₁ to 9 corresponding to the channels
From D / A conversion circuits 8 ₁ to 8 _n corresponding to 9 _n , decoders 7 _{1 to} 7 _n for decompressing the supplied compressed video signal, and a multiplexer 6 that arranges the supplied compressed video signal in time division It is configured. Each of the decoders 7 _{1 to} 7 _n includes a buffer for temporarily holding the supplied compressed video file.

Here, in this embodiment, the disks 2 ₁ ...
2 _m and controllers 3 _{1 to} 3 _m are SCSI (Small Co
mputer System Interface), the controllers 3 _{1 to} 3 _m and the buffers 4 ₁ to 4 _m are connected to the DMA (Di
rect Memory Access). Also,
Whether or not blocks having these functions are provided in one device has nothing to do with the present invention. Furthermore, when the compressed video signal is supplied from the input terminal 12, the head block of the supplied compressed video signal is stored in the RAM 5
It is also possible to write to.

Here, FIG. 2 is a schematic diagram showing an example of the operating principle of the disk of the present invention. In FIG. 2, a state in which the disk head is seeking is shown by a dotted line. In one example of this video-on-demand system, seven programs, that is, compressed video signals are registered in the disc,
The number of channels that can use the registered program is five. In this system, FIG. 2A shows an example of the operation of the disk head when the programs 1, 2, 4, and 5 are already reproduced for the four channels 1, 2, 3, and 4.

Then, as shown in FIG. 2B, when the reproduction request of the program 7 is issued from the channel 5 at the position of the arrow, conventionally, it is necessary to wait a maximum of T1 + T2 hours. However, as soon as the reproduction request of the program 7 is issued, the compressed video file of the first block of the compressed video signal is read from the RAM arranged in parallel with the disk, reproduced, and supplied to the channel 5. At this time, the compressed video file read from the RAM is supplied at the normal timing of being read from the disk.

Here, FIG. 3 shows an example in which the programs 1 to 7 are divided into blocks. As shown in FIG. 3, all programs are divided into predetermined blocks, and the first block of the divided blocks is called a first block. Further, the divided blocks are further divided for recording on the discs 1 to m. In other words, the block unit is m times the unit recorded on the disc. here,
The x of xK indicates the order of writing and reading.

Here, FIG. 4 shows an example in which the encoded data of one program is recorded in a plurality (m) of disks in units of K [Mbit]. That is, the first K [Mbit] of the compressed video signal is the disc 1, the next K [Mbit] is the disc 2, and so on.
[Mbit] Each of the discs 1 to m is repeatedly written in order. As a result, the compressed video signal is held on the disc as a K [Mbit] file (hereinafter referred to as a compressed video file).

Here, FIG. 5 shows an example of the programs 1 to 7 recorded on the disks 1 to m. In the disks 1 to m, the first block (P1 ₁ ) of the program 1, the second block (P1 ₂ ) of the program 1, ..., The a-th block (P1 _a ) of the program 1, the first block (P1 _a ) of the program 2 ( P2 ₁ ), the second block of program 2 (P2 ₂ ),
.. are recorded in the order of the b-th block (P2 _b ) of the program 2, the first block (P3 ₁ ) of the program 3, ...

The CPU manages a plurality of (m) disks like one disk. The vertical data strings in FIGS. 4 and 5 are managed with the same address. As a result, the heads of the m discs all move along the same locus. Further, the CPU manages a block address for each compressed video file. FIG. 6 shows an example of the management table. The management table in FIG. 6 shows the sector numbers of the disc. The method of using such a disk is called striping.

When the system is activated, the CPU refers to the management table shown in FIG. 6 to read the head block of each compressed video signal from the disk and write it in the buffer. Next, RA placed in parallel with the disk via a multiplexer
Write to M. At this time, the CPU determines the address of the first block of the management table from the disk address to the RAM.
Change to the address of.

The reproduction request from the terminal is first supplied to the CPU, and the CPU detects the RAM address of the head block of the requested program from the management table regardless of the current position of the head of the disk, and sends it to the multiplexer. Output. And at the next block read sequence,
Scheduling is performed so that the second block of this program is read from the disk.

With respect to the programs written in the RAM, there are cases where all the programs can be written in the RAM and cases where only some of the programs can be written in the RAM depending on the capacity of the RAM. Here, when only some programs can be written in the RAM, the CPU stores the request frequency of the programs,
It is possible to select any method such as writing to the RAM in order from the program with the highest request frequency.

Here, FIG. 7 is a flow chart showing an example of system activation of the multi-channel video reproducing apparatus of the present invention. This flowchart is started from step 21, and if there is an unwritten compressed video file in step 22, the first blocks of all the compressed video signals recorded on the disk, that is, the first blocks are written to the RAM as the compressed video file. Is determined. That is, if the head portions of all the compressed video signals recorded on the disk are recorded in the RAM as compressed video files, the control moves to step 28, and this flowchart ends. If the head portion of all the compressed video signals recorded on the disk is not recorded in the RAM as a compressed video file, the control moves to step 23.

In the address detection of step 23, the address of the first block of the compressed video signal for which video reproduction is requested is detected from the management table of the compressed video file,
Control transfers to step 24. In the writing to the buffer in step 24, in step 23 (address detection), the first data from the disk is read based on the detected address.
The compressed video file of the block is read and written to the buffer. In the reading to the multiplexer in step 25, the compressed video file written in the buffer is read from the buffer to the multiplexer, and in step 26.
Control is transferred to.

In the writing to the RAM in step 26, the compressed video file is fetched from the multiplexer, and the fetched compressed video file is written to the RAM.
Then, in the address change of step 27, the address of the first block of the management table of the compressed video file is changed from the address of the disk to the address of RAM, and step 22 (there is an unwritten compressed video file).
Control is transferred to. That is, this flowchart is controlled until the first blocks of all the compressed video signals recorded on the disc are written in the RAM as compressed video files.

Here, FIG. 8 is a flow chart showing an example of the reproduction request response of the present invention. The control of this flowchart is started from step 31, and step 3
When the video reproduction request of 2 is made, the terminal requests the CPU to reproduce the video. In the address detection in step 33,
The address of the compressed video signal for which the CPU is requested to reproduce the video is detected from the management table of the compressed video file.
That is, the address of the RAM in which the first block of the compressed video signal is recorded as the compressed video file is detected.

In reading from the RAM in step 34,
In step 33 (address detection), the compressed video file is read from the RAM according to the detected address, and the control moves to step 35. In the data writing of step 35, in step 34 (reading from RAM), the compressed video file read from the RAM is written as data to the bus slot of the channel for which video playback is requested.
In the data reading in step 36, the compressed video file written in the bus slot in step 35 (data writing) is read from the predetermined bus slot by the decoder.

If there is a block in step 37, it is judged whether or not all the blocks of the compressed video signal for which video reproduction is requested have been reproduced, and if all blocks have not been reproduced,
Control is transferred to step 38. In the address detection of step 38, the CPU detects the address of the next block recorded on the disk from the management table of the compressed video file. Then, in the writing to the buffer in step 39, in step 38 (address detection), the compressed video file is read from the disk based on the detected address and is written in the buffer.

The compressed video file written in the buffer is written as data in step 35 (data writing) into the bus slot of the channel for which the video reproduction request is made. Step 36
Also in (data reading), the same control as described above is performed, and in step 37 (with block), if all the blocks of the compressed video signal for which video reproduction is requested as described above are reproduced, control is passed to step 40. Then, this flowchart ends.

In this embodiment, the RAM is used as the storage means arranged in parallel with the disk, but the head block of the compressed video signal stored in the disk is stored in advance in a batch recording type memory, that is, FLASH. It is also possible to use the FLASH memory by recording in the memory.

[0037]

According to the present invention, it is possible to eliminate the waiting time that is required after the user makes a reproduction request for a video signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a multi-channel video reproducing device of the present invention.

FIG. 2 is a schematic diagram showing an example of the operating principle of the disk according to the present invention.

FIG. 3 is a schematic diagram showing an example of a divided program according to the present invention.

FIG. 4 is a schematic diagram used for explaining that a compressed video file according to the present invention is held on a disc.

FIG. 5 is a schematic diagram showing an example of a program recorded on a disc according to the present invention.

FIG. 6 is a schematic diagram showing an example of a management table of a compressed video file according to the present invention.

FIG. 7 is a flowchart showing an example of system startup of the multi-channel video reproducing device of the present invention.

FIG. 8 is a flowchart showing an example of a reproduction request response of the present invention.

FIG. 9 is a schematic diagram illustrating an example of a video on demand system.

FIG. 10 is a block diagram showing an example of a conventional video reproducing apparatus.

FIG. 11 is a block diagram showing an example of a multiplexer.

[Explanation of symbols]

 2 disk 3 controller 4 buffer 5 RAM 6 multiplexer 7 decoder 8 A / D conversion circuit 11 network interface 14 CPU 15, 16 timing control circuit

Claims (3)

[Claims] 1. A video-on-demand system, comprising a RAM arranged in parallel with a disk holding a plurality of compressed video signals, and a head data block of the plurality of compressed video signals held on the disk. Is stored in the RAM. 2. A video-on-demand system, comprising: a flash memory arranged in parallel with a disk holding a plurality of compressed video signals, and head data of the plurality of compressed video signals held on the disk. A multi-channel video signal device characterized in that blocks are stored in the FLASH memory. 3. The multi-channel video signal apparatus according to claim 1 or 2, wherein the compression applied to the video signal is MPEG2.