EP0283350A1 - Broad-band host, particularly for the transmission of music or images - Google Patents

Abstract

A broadband host is defined by a main processor (10) communicating via a channel (DMA 15) with a hard disk (16), on the one hand, and output boards (2-1 to 2-16) on the other hand. Each board comprises its own processor which manages, in double-access and toggle mode, two buffer memories A and B. Whilst one delivers musical information to the user, the other is filled, and vice versa. …<IMAGE>…

Description

The invention relates to telematics, in particular on videocommunication networks, as well as on the integrated services digital network.

It is for example interesting to be able to transmit, in its high fidelity, the discographic novelties published in the month. A similar problem can arise for the transmission of new images.

We currently have means for the permanent archiving of data such as non-erasable digital optical discs (writable once to be read several times or "WORM", compact disc memories (or "CD ROM") or even discs "audio" compacts. With regard to presenting new products on a monthly basis, it is hardly conceivable to do so by distributing such storage media.

The object of the present invention is to allow such distribution using an n-times rewritable system, such as one or more magnetic disks.

It is therefore a matter of being able to deliver mass data in real time, at a rate of up to 768 kilobits per second, and this towards a fairly high number of simultaneous users, for example on at least 16 consultation stations. It is also required that the system can manage several gigabytes of mass memory.

We already know computer servers. In these, the processor will look for data on a mass memory, which can be a magnetic disc or an optical disc, then it sends them on the output channel (s), by passing them through its registers or by the central memory.

The theoretical speed limit obtained, for data processing, with such a server, is equal to approximately half of the maximum speed of the bus. In practice, the speed is much lower, because communications between the processor and the peripherals must also circulate on the bus.

For example, to process 16 output channels at a rate of 384 kilobits per second, you would need a bus operating at least 2 megabytes per second, which is only found on large and very expensive systems. This explains why there is no server on the market, in particular multi-channel, having the capacity to deliver information at 384 kilobits per second, for example.

The present invention aims to provide a solution to this problem, by proposing a new multichannel server structure, capable of operating in broadband, that is to say at a high transmission rate.

The proposed device comprises in combination:
- a main processor, having one or more direct memory access channels (or DMA),
- a large capacity mass memory, for example kind to one or more hard disks, connected to this or these direct memory access channels, and
a plurality of output units, also connected to the direct memory access channel, and each having two buffer memories of the same capacity, with dual access, managed in toggle mode by an auxiliary processor, which is capable of emptying these alternating memories without discontinuity, while authorizing each time rapid filling of that of the two buffer memories which is inactive in reading, with new information.

In a particular embodiment, the buffer memories, 128 kilobytes in length, are managed by a 16-bit word processor, clocked at 8 MHz.

For its part, the main processor, with 16-bit words and clocked at 8 MHz, manages a catalog located in at least one hard disk from mass memory (preferably in each of the hard disks if there are several) . These hard disks have a positioning time of their heads at most equal to approximately 25 milliseconds (for 16 channels), as well as a reading speed of the order of 2 Megabytes per second. This allows 128 kilobytes to be loaded into the buffer in less than 0.15 seconds. It then becomes possible to process the 16 output units continuously, which each deliver their information at just over 48 kilobytes per second to deliver 384 kilobits of sound per second.

The output data can be converted to analog form either immediately or after transmission over a suitable link.

According to another aspect of the invention, a serial interface is provided allowing the main processor to receive information to be stored in mass memory, this storage taking place in distributed form, taking into account buffer capacity. The information to be stored advantageously comes from a general server center, by fast digital network or by satellite.

In the preferred application, the output units are connected to consultation stations for listening to music or viewing images on demand.

In particular, the consultation stations can be associated with interrogation means, in particular Minitels, allowing the selection of a piece of music or a set of images from the broadband server, which is associated with a multichannel telematics server for processing this selection information.

• - la figure 1 est le schéma de principe d'un serveur à large bande selon l'invention;
• - la figure 2 est le schéma de principe d'une carte ou unité de sortie du serveur de la figure 1;
• - la figure 3 est un diagramme fonctionnel montrant le fonc­tionnement du serveur à large bande de l'invention;
• - la figure 4 est un chronogramme vertical montrant le transfert de données entre le disque dur et une mémoire tampon de l'une des voies de sortie;
• - la figure 5 est un chronogramme vertical montrant le tra­vail du serveur selon l'invention en relation avec les deux mémoires tampon d'une même voie de sortie;
• - la figure 6 est un schéma plus général montrant une ins­tallation complète utilisant le serveur à large bande selon l'invention; et
• - la figure 7 est un diagramme illustrant les liaisons sus­ceptibles d'intervenir dans une installation complète selon la figure 6.

Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

• - Figure 1 is the block diagram of a broadband server according to the invention;
• - Figure 2 is the block diagram of a server output card or unit of Figure 1;
• - Figure 3 is a functional diagram showing the operation of the broadband server of the invention;
• - Figure 4 is a vertical timing diagram showing the transfer of data between the hard disk and a buffer memory of one of the output channels;
• - Figure 5 is a vertical timing diagram showing the work of the server according to the invention in relation to the two buffer memories of the same output channel;
• - Figure 6 is a more general diagram showing a complete installation using the broadband server according to the invention; and
• FIG. 7 is a diagram illustrating the connections liable to occur in a complete installation according to FIG. 6.

The attached drawings essentially contain certain information. Consequently, they will not only make it possible to better understand the detailed description below, but also to contribute to the definition of the invention, if necessary.

In Figure 1, the broadband or SLB server is located in the dashed frame referenced 1.

It comprises a main processor 10, with 16-bit words and clocked at 8 MHz. This processor 10 has a local bus BL which communicates with a random access memory 11, a program memory not shown, and a serial interface 12. Other devices can naturally be provided.

The serial interface 12 is linked to a telematic server 4 to which we will return later.

The processor 10 also communicates by a link B with a direct memory access channel or DMA channel denoted 15. This DMA channel allows the processor 10 to manage one or more hard disks 16 of large capacity. It is also connected to a series of output cards 2-1 to 2-16, to serve here 16 consultation stations, that is to say 16 users.

The diagram of one of the cards 2 is given in Figure 2.

Each of these cards includes a processor 20, which is also 16-bit word and clocked at 8 MHz. It is provided with a program read-only memory 21, as well as a working working memory 22.

The main function of processor 20 is to manage two buffer memories 25A and 25B, both of capacity 128 kilobytes.

As shown schematically by the input 24 and output 26 switches, these two buffer memories are managed toggle, that is to say that when, for example, the buffer memory 25A delivers data to the output, the processor 20 makes it impossible to enter data into this memory 25A. On the other hand, at the same time, it is possible to introduce data into the buffer memory 25B. The situation is reversed when switches 24 and 26 change state.

These buffer memories 25A and 25B are also dual-access, that is to say that they can be controlled not only by the processor 20 which is part of the same output card, but also by the main processor 10.

It is considered that such double access is known to those skilled in the art. The means necessary for the realization of the double access in itself have not been shown, the switches 24 and 26 constituting a schematic representation.

It will simply be specified that the switching between the two buffer memories 25A and 25B is entirely under the control of the local processor 20 of the output card concerned.

The stage illustrated in 29 recalls that one can immediately proceed to a digital / analog conversion. We can also be content to transmit the information either to a local consultation station, or on a link to a remote consultation station.

The main processor 10 performs the essential function of managing the catalog of the hard drive or drives 16. If there are several hard drives, it is preferable to install the catalog on each of these.

We will see below how this catalog is defined.

One of the starting points of the invention is the following remark: the main processor only has to carry out elementary instructions of the kind:
- take data first,
- put them in a second point.

To achieve this, it is absolutely useless to have recourse to a refined central processor comprising a set of several hundreds of instructions, for example like the processors of the systems having a bus with 2 Megabytes per second. A simple processor like those of universal microcomputers, or even a processor with reduced instruction set, is much better.

This will be better understood on examining FIG. 3, in which the broadband server SLB is shown at 1, however, apart from its hard disks 16, and its outputs to the terminals (to which we have given the same numbers as the exit cards).

FIG. 3 also shows information coming from the telematic server 4. It also shows at 110 the file management system which the broadband server 1 must have.

To fix the ideas, it is supposed that the server delivers high fidelity music information and a file corresponding to a piece of music is defined by a three-digit number.

Thus, the telematic server 4 will give the broadband server 1 instructions such as: deliver the file 231 on channel 12, deliver file 056 on channel 7, interrupt the delivery of file 022, deliver file 189 on channel 13, interrupt the delivery of file 206.

In response to these commands from the telematic server 4, the broadband server will carry out transfers illustrated inside the block 110, which is distributed in a number of lines equal to the number of channels served.

The process 1 consists for example of filling the memory 25A of the card 2-1 with the data block located at the address XXXXXXXXXX of the mass memory.

Process 2 consists in delivering to the memory 25A of channel 2-2 the block located in the hard disk at the address YYYYYYYYYY.

Process 3 consists in delivering to the memory 25B of channel 2-3 the block located at the address ZZZZZZZZZZ. Thus, the process 15 consists in delivering to the memory 25B of the channel 2-16 the block located at the address UUUUUUUUUU. Finally, the process 16 consists in delivering to the memory 25A of the channel 2-16 the block located at the address VVVVVVVVVVV.

It will be observed that the processor 10 communicates with the telematic server 4 only at the level of complete files each corresponding to a piece of music.

On disks, the data is organized in blocks of fixed size, size which is preferably quite large, for example 1024 bytes.

On the other hand, the processor 10 is content to increment block addresses for the DMA channel during the reading.

In short, the telematic server sends the following orders:
- send piece X on channel n,
- stop song X.

The broadband server can respond:
- song X temporarily unavailable,
- physical problem on track n.

Reference is now made to FIG. 4.

On receipt of a read order for a file x, and if all the tasks in progress are executed, the main processor 10 searches for the physical address of the requested file in the catalog located at the head of each of the disks.

The microprocessor 10 will then seek the beginning of the file X by a DMA line, to store it in the buffer 25A of the output channel 2-n concerned.

The processor 10 begins by requesting a positioning of the read head of the hard disk concerned. We now know how to make hard disks capable of positioning the head in a time at most equal to 25 milliseconds.

Processor 10 will only be occupied for the first two or three milliseconds. He therefore has 22 milliseconds left, during the read head positioning time, to take care of various system tasks, as well as to prepare the following process.

A little before the end of the 25 milliseconds, the processor 10 initiates the transfer order from the hard disk 16 to the output channel 2-n concerned. The data reading speed being 1.96 megabytes per second, and the processor 10 being clocked at 8 MHz, those skilled in the art will understand that it is very easy to load a memory. buffer in less than 150 milliseconds, including hard drive read head positioning time.

FIG. 5 now shows how different operations relating to different exit channels are nested.

The process to be executed for the different output channels has been defined in connection with Figure 3.

In FIG. 5, it is assumed for example that the process of rank n has been carried out allowing filling of the memory A of the channel 20-n. It is assumed that this is the first filling, that is to say the beginning of a music file.

After that, the processor of the broadband server 1 can take care of other processes X, Y and so on, each occupying a time of 0.15 seconds.

After 2.40 seconds, it must be returned to process n, this time to fill memory B of channel 20-n with the rest of the music file corresponding to process n.

FIG. 5 shows that this occurs just before the end of the emptying of the memory 25A of this same channel 20-n.

It is thus ensured that the local processor of the 2-n output card concerned is able to deliver in a completely continuous manner, seen from the user, the high fidelity musical information that the user has requested.

The emptying time of a buffer memory A is 2.67 seconds.

If we add the filling time of memory A, we arrive at 2.82 seconds.

The time interval between the end of filling of memory B and the end of emptying of memory A is 0.27 seconds (2.82 - (2.40 + 0.15)).

It will also be observed that the process of emptying the buffer memories is done channel by channel, under the control of the local processor 20 of each of the output cards. This process is therefore completely asynchronous.

On the other hand, as the filling speed is much higher than the emptying speed, it is naturally the local processor 20 of the output card concerned which alone can authorize filling. This order is only given when the emptying of the corresponding buffer memory is effective. The processing time of a sample is 1/32 thousandth of a second. For a processor clocked at 8 MHz, there are therefore 250 cycles at the end of the block of a buffer memory 25A to pass to the head of the block of the buffer memory 25B.

The processor 20 is of course also responsible for shaping the data and sending it to the decoding cards.

Reference is now made to FIG. 6.

We find there the broadband server 1, whose output channel 2-i remotely feeds a digital / analog converter 29 which delivers music information for example to a high fidelity headset 30.

Through the interface 18 defining a direct memory access channel, the server 1 communicates with hard disks 16.

It also communicates through a serial interface 12 and a parallel interface 13 with corresponding interfaces 42 and 43 of the telematic server 40, which can be a conventional multichannel server for digital information. risk at normal rate. The output channels V1 to Vn communicate for example with Minitels such as M30.

A serial input interface 49 is also provided, as well as a CCITT interface, noted 48.

These two interfaces communicate with the corresponding interfaces of a general server center, which may be unique at the national level. It will therefore be referred to below as the national CSN server center.

This server center includes a computer, the bidirectional serial interface 59 communicates with the interface 49, for example via a public telecommunications network. Its directional interface 58 sends information to the interface 48 at a high rate, for example via a link by the TELECOM 1 satellite, the rate being 64 kilobits per second.

The computer 50 has an interface denoted 54 and forming a direct memory access channel for hard disks 56. It also has an analog / digital conversion input 55 suitable for receiving stereophonic musical signals with two channels L and R (for left and right) of an input string 60.

Figure 7 shows variants. First, the input chain 60 can be separated from the national server center 50. The service information is then transmitted through the TRANSPAC network or the switched telephone network.

Useful information can be transmitted at a high rate by the TELECOM 1 satellite, by TRANSPAC, by the integrated services digital network, or by a video communications network.

Transmission can also take place between the center national server 50 and each of the local servers, which each bring together the broadband server proper 1, and the associated telematic server 4.

Finally, the local consultation stations can be located in the same place as the broadband server 1. But they can also be placed remotely. In such a case, information can be exchanged through the integrated services digital network, the switched telephone network, or video communications network.

For their part, useful musical information can be transferred by the integrated services digital network, or by a video communications network.

An example of the application of the invention will now be described. The input station 60 can be a conventional sound input system, to obtain very good sound quality. We make sure that the converter 55 allows stereo input at 384 kilobits per second per channel. At the level of the national server center, the computer 50 ensures the recording on the hard disk (s) 56 (of very large capacity) of the music pieces in the form of frames from 64 kilobits to 384 kilobits per second and per channel. This is done through the SMD interface.

At the same time, a selection database is updated. It is distributed to local servers through the switched telephone network.

Systematically, or on request, the national server center can refresh the mass memories of the local servers by the unidirectional channel defined through the CCITT interfaces (V35 or X21).

The communication which takes place in parallel, for example by the telephone network switched over the serial interfaces allows the exchange of service information, in particular the operating balance of music pieces stored on the local server, since the last transmission. Updates are also carried out, which can be specific to each local server. The service road may also allow certain remote maintenance.

Of course, it will often be preferable to transmit the new pieces of music to the broadband server at night, so that the system is available during the day to serve the users.

It is assumed that the transmission takes place continuously and simultaneously for all the local servers. It is also admitted that these perform the recording continuously.

In this recording phase, control is ensured by the broadband server 1 from the interface V35 or X21 of the computer 4 to which it is connected by the parallel interfaces 13 and 43.

In practice, the telematic server receives the data block by block. It ensures good parity of the samples, and invalidates the blocks which have more than two successive erroneous samples. Each of the blocks is naturally identified by a number.

Once a block is validated, it can be stored on the local hard drive, while keeping its serial number, which has no relation to its physical address on the hard drive.

Only the local system manager knows the physical address of the songs on the hard drive.

The operating system of the broadband server is responsible for managing the catalog of hard disks, and in particular the sectors which may have a physical problem and are noted in a report.

The probability of having an incorrect block per session is around 10 de³ for a transmission of 10⁸ samples. Therefore, a very low speed link between the national server center and each telematic server is sufficient to make the corrections.

Only the broadband server is responsible for managing the hard disks as already indicated. In the event of a writing problem, it can report the problem but still try to relocate the data block that gave rise to this problem. Since only the system manager has write rights, there is no mutual exclusion problem with the hard drives of broadband servers.

In summary, the proposed device comprises an architecture distributed horizontally and vertically. As a result, at no point in the system is the speed required colossal.

On hard drives, data is organized into fairly large, fixed-size blocks.

In server mode, the system quickly performs simple operations, which allow it to safely serve users with musical information without discontinuity, despite the sequential block processing of this information.

The device according to the invention takes full advantage with the availability of very large capacity hard disks (several hundred megabytes, at affordable economic conditions).

Claims (9)

1. Electronic device suitable for forming a broadband server, in particular for transmitting music or images, characterized in that it comprises, in combination:
- a main processor, having a direct memory access channel,
- a large capacity mass memory of the hard disk type, connected to this direct memory access channel, and
a plurality of output units, also connected to the direct memory access channel, and each having two buffer memories, of the same capacity, with dual access, managed in toggle mode by an auxiliary processor, suitable for emptying these memories alternating without discontinuity, while authorizing each time rapid filling of that of the two buffer memories which is inactive in reading, with new information. 2. Device according to claim 1, characterized in that the buffer memories, 128 kilobytes in length, are managed by a 16-bit word processor, clocked at 8 MHz. 3. Device according to one of claims 1 and 2, characterized in that the main word processor of 16 bits, and clocked at 8 MHz, manages a catalog located in at least one hard disk of the mass memory, which has a positioning time of its head at most equal to approximately 25 milliseconds, for a reading speed of the order of 2 megabytes per second, which makes it possible to load 128 kilobytes in buffer memory in less than 0.15 seconds, and thereby the continuous processing of 16 output units which deliver their information at around 48 kilobytes per second. 4. Device according to one of claims 1 to 3, charac terized in that there is a digital / analog conversion or any other form of decoding of the output information. 5. Device according to one of the preceding claims, characterized in that it comprises a serial interface allowing the main processor to receive information to be stored in mass memory, the storage taking place in distributed form, taking into account the capacity buffer memories. 6. Device according to claim 5, characterized in that the information to be stored comes from a general server center, by digital medium or high bit-rate network of switched or non-switched type such as videocommunication networks, the integrated digital network services or by satellite. 7. Device according to one of the preceding claims, characterized in that the output units are connected to consultation stations for listening to music or viewing images, possibly on demand. 8. Device according to claim 7, characterized in that the remote consultation stations are associated with interrogation means, in particular Minitel, allowing the selection of a piece of music or a set of images with the broadband server, while the latter is associated with a multichannel telematic server for processing this selection information. 9. Device according to claim 7 or claim 8, characterized in that the musical or visual information is readable simultaneously by several consultation stations.

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