FR2654282A3 - METHOD OF TRANSMITTING, IN PARTICULAR OF TELECOPIES, TO A RECEIVING APPARATUS WITH A LIMITED PROCESSING SPEED, AND APPARATUS FOR IMPLEMENTING SAID METHOD - Google Patents

Abstract

The reception apparatus being provided with a buffer memory, the transmission side is simulated (103, 104, 202, 203), the filling and emptying of this buffer memory, and the flow of the useful information is slowed down (106) when the simulation indicates the occupation of a determined fraction of the capacity of the buffer memory by useful information. The value of the capacity of the buffer memory, as well as that of its emptying speed, are acquired during a protocol procedure preceding the transmission of the useful information. The invention applies in particular to transmission by fax.

Description

The present invention firstly relates to a transmission method,

  in particular faxes, to a reception apparatus whose speed of processing useful information is limited, in which the rate of useful information transmitted in response to the achievement of a condition related to the limit value of said speed is slowed down.

treatment.

  Such a method makes it possible to ensure, for any document

  fax, for example, a trans-

  mission as short as possible, taking into account the

  maneuvers from the receiving device to which it is sent.

  We already know a process of the type defined above, used

  This process uses the fact that, on transmission, any document to be transmitted is broken down into a series of lines of pixels that are individually coded, and that, at the reception, each line of code is decoded. pixels received and printed on it, in the rest of the text, we will call line not a line of characters of a text possibly supported by the document, but a line of pixels of the document Such a line is a band document, of equal height to

  that of a pixel, or elementary point of image and of

  equal to the width of the document, which corresponds

  example, for a document in A 4 format, 1728 pixels.

  In the case of facsimile, the processing speed at the reception is limited because the printing time of a line of pixels is non-zero, and is worth, for example

  ms regardless of the configuration of the line.

  In the known process, during the procedure,

  protocol length that precedes the transmission of useful information, the value of the time required for the receiving apparatus to print a line of pixels The coding of each pixel line is then performed This coding is such that the volume of useful information For example, the volume of useful coding information for an all-white pixel line is very small, while the volume of coding useful information for a pixel line exhibiting many black and white ranges is more important The maximum flow of the information transmitted being imposed elsewhere, it is determined, before the transmission of useful information for coding a row of pixels, the time required for the transmission of this information to this maximum rate When this duration is less than the duration of printing of a line by the receiving apparatus, the rate of the useful information transmitted is slowed down so that the duration of transmission relative to a line always remains at least equal to its duration of printing by the receiving apparatus. This avoids, for sure, the overflow of memory

  buffer, of a necessarily limited size, provided for in

  reception, especially because we have to wait until we have received all the relevant information

  to a pixel line before decoding.

  In the known method, therefore, the rate of the useful information transmitted is constantly adjusted to the limit value of the printing speed of the reception apparatus, since the duration of transmission of a pixel line, and therefore its duration reception, is made at least equal to the duration

  of printing this line Thus, the speed of filling

  wise the buffer is, for sure, inferior or

equal to its emptying speed.

  This known method, however, has a disadvantage, related to the fact that the rate of useful information is systematically slowed for any line whose duration of transmission at the maximum rate would be too short Or, when such a line is followed by a line of which the duration of issue is long, such a slowdown is not necessary In this case, the difference between the printing duration and the transmission time at the maximum flow of the first line could be taken advantage of

  to start issuing the second line In the

  known, therefore, time is lost in the case of alternating lines with short emission times and

long emission times.

  The present invention aims to overcome the above disadvantage. For this purpose, it relates to a method of the type defined above, characterized in that, said receiving apparatus being provided with a buffer memory, the filling and emptying of said buffer memory is simulated, and said condition is the occupation of a certain fraction

  the capacity of said buffer.

  In the process of the invention, it only slows down

  the flow of useful information, ie

  say only when the buffer on receipt

risk of overflowing.

  As a result, the transmission time of a document is, on average, shorter with the method of the invention than with the known method. It should be noted that this remarkable result is obtained especially because it is simulated, on the sending side, the filling and emptying of the buffer of the receiving apparatus In fact, without this

  simulation, it would be necessary to avoid slowing down

  unnecessary, the receiving device will let the sending device know that its buffer is approaching saturation. This would result in a loss of

  time, in particular for the reversal of each of the

  It is a turnaround for demodulators, or modems, implemented in facsimile, a turnaround necessary for the transmission of information from reception to transmission. In such a case, the time thus lost might not be compensated for by the time saved because of the delay. no slowdowns

unnecessary flow on the issue.

  In the preferred implementation of the method of the invention: any document to be transmitted is broken down into a series of lines of pixels,

  each pixel line is coded using binary elements

  encoding numbers, in variable numbers from one pixel line to another,

  add the number of binary coding elements of each

  line to be transmitted to a variable representative of the number

  total number of bits stored in said buffer memory

  pon, in order to simulate the filling thereof, the number of coding bits of each line to be transmitted is stored, subtracted periodically, with a period equal to the duration of printing a line by the device the number of coding bits per line to be transmitted which has been stored for the longest time, in order to simulate the emptying of said buffer memory, and the number of bits of

  line coding to be issued which has just been subtracted.

  Such an implementation is particularly simple.

  Advantageously, fixed rate information is transmitted, said transmitted information comprising useful information and stuffing information, and the proportion of stuffing information in said information transmitted is increased to slow the flow rate.

useful information.

  In this case, the implementation of the method of the invention is further facilitated by the fact that this is already done on the known apparatuses in order to vary the flow rate of the

useful information.

  Advantageously, one acquires, during a procedure

  protocol duration preceding the transmission of useful information, the limit value of said processing speed

  and the value of the capacity of said buffer.

  Adaptation to the possibilities of the receiving device

is possible.

  The present invention also relates to a fax transmission apparatus for implementing the method

  preceding, intended to send faxes to an

  receipt of which the speed of processing information

  Useful information is limited, transmission apparatus comprising means for slowing the flow of useful information in response to means for determining the achievement of a condition related to the limit value of said processing speed, characterized in that, said reception apparatus being provided with a buffer memory, said means for determining the realization of the condition comprise means for simulating the filling and emptying of said buffer memory and means for determining the occupation of a determined fraction of the capacity of said buffer.

  The present invention will be better understood thanks to the

  following description of the preferred implementation of the method of the invention, as well as of the preferred embodiment of the apparatus of the invention, with reference to the accompanying drawings, in which: FIG. blocks of a fax machine, and

  Figures 2 and 3 show diagrammatic diagrams.

  the operating steps of the apparatus of the

figure 1.

  FIG. 1 shows a transmission apparatus,

  here to send faxes

  to a reception apparatus not shown, by the

  via a telephone line 5.

  As has already been pointed out, the invention relates to a method of adapting the flow of useful information.

  issued to the performance of the receiving apparatus,

  training in speed of information processing.

  useful information, limited here by the speed of printing.

  Here, and in known manner, the receiving apparatus prints the documents it receives pixel line by pixel line, and its printing speed is limited because

  the printing time of a line of pixels is 10 ms.

  The transmission apparatus of FIG. 1 comprises a device 1 for analyzing the document 6 to be transmitted, a circuit 2 for encoding information resulting from the analysis of the document 6, a circuit 3 for managing communications, and a

  modem 4 connected to a telephone line 5.

  The analysis device 1 is of the known type which analyzes, row of pixels per line of pixels, the document 6 It is provided with an output which delivers an analysis signal A for

each line of pixels analyzed.

  The coding circuit 2 is of the known type provided with an input receiving the analysis signal A and an output

  delivering a coding signal C for each pixel line.

  The encoding implemented results, for example, in a known way, from the decomposition of each line of pixels into a series of pixel ranges, the pixels of a range having all the same value, either black or white, in the case binary pixels of black or white value The signal C then indicates, for each pixel line, and in a coded manner, the number and the value of the pixels.

  pixels in each of the successive ranges of the line.

  The communications management circuit 3 is provided with a first input receiving the signal C, a second input receiving a signal R and an output delivering a signal.

  signal E It will be described in more detail later.

  The modem 4 is provided with an input receiving the signal E,

  an output delivering the signal R, and bidirectional access

  In known manner, it modulates the signal E to transmit it, via line 5, to the receiving apparatus. Similarly, the modem 4 demodulates the signals it receives on the telephone line 5. line 5

  from the receiving device to give birth to

  It should be noted that, in most cases, the transmitting apparatus of FIG. 1 is also arranged to receive faxes. However, this is not compulsory and does not intervene in the present invention. For this reason, any circuits and devices necessary for the operation of the apparatus of Figure 1 as receiving apparatus are not shown in this figure. The operation of the apparatus which has just been described

is the next.

  First, the transmitting apparatus calls the apparatus of

  receipt to which he must transmit document 6

  communication is established, it engages, in a known manner, between the two devices, a protocol procedure which precedes the transmission of the relevant information relating to

  in document 6, which allows for a mutual exchange of informa-

  tions, exchange intended to prepare this program

  protocol procedure is standardized by the Advisory Committee

  International Code for Telegraph and Telephone, or

C.C I T T.

  During this protocol procedure, it is provided, in known manner, the acquisition by the transmitting apparatus

  the value of the printing time of a line by

same reception.

  The method of the invention further provides for the acquisition by the transmitting apparatus of the value of the capacity of the

  buffer which is provided with the receiving apparatus.

  It is recalled that this buffer memory is necessary from

  that the receiving machine prints the document

  received line of pixels per pixel line, wait until you have received and decoded a complete pixel line before printing In principle, the capacity of the buffer corresponds to a few lines of pixels For example, the capacity of the buffer memory is 432 bytes, During the protocol procedure, and in a known manner, the quality of the transmission channel is tested, and the maximum rate at which the information on this channel can be transmitted is determined. ,

  so that the error rate on reception remains acceptable.

  If the quality of the transmission channel is good, the bit rate is 9600 bits / s. If the quality of the transmission channel is average, the bit rate is 4800 bits / s and

and so on.

  After the protocol procedure, the duration of printing of a line by the receiving apparatus, the capacity of the buffer of the receiving apparatus, and the maximum bit rate of the information on the transmission path are known to the user. transmission apparatus, and more specifically by the communications management circuit 3 which is a

microprocessor circuit.

  The transmission of the useful coding information of the lines of pixels of the document 6 represented by the signals C, then begins. To ensure that the transmission time of the document is as short as possible, the first useful information is sent at the maximum rate, which is assumed to be equal, by

for example, at 9600 bits / s.

  However, if the first lines of pixels of the document are simple lines, whose coding requires only a few bits, the transmission duration of each of these lines may be less than 10 ms, and in this case there is has a risk of overflow of the buffer of the receiving device Indeed, the duration of reception of each of these lines will be less than 10 ms, and the speed of filling of the buffer greater than its emptying speed, since this depends on the duration of printing

of a line, here equal to 10 ms.

  If, on the other hand, the first lines of pixels of the document are complex lines, the coding of which requires a large number of bits, the transmission duration of each of these lines will certainly be greater than 10 ms, even at a bit rate of 9600 bits. / s On the receiving side, there will be no risk of overflow of the buffer, since its speed of

  emptying will be greater than its filling speed.

  Thus, in certain situations, it is necessary to slow the flow of the useful information transmitted, while in other situations, it is necessary to leave this flow equal to the flow rate.

  maximum compatible with the quality of the transmission channel.

  sion, if it is desired that the total duration of transmission

  a document is as small as possible.

  In order to decide in which situations the rate of useful information transmitted must be slowed down, the present invention proposes the simulation, on the transmission side, of the filling and emptying of the buffer which is on the reception side, the decision to slow down being taken when the

  simulation indicates that a specific fraction of the capacity

  city of the buffer is busy.

  The fraction of the capacity of the buffer memory whose

  cupation triggers the slowdown is determined in particular with regard to the value of the maximum flow rate used, so that the risk of overflowing the buffer there after slowdown is virtually zero This fraction can be, for example, 1/10 th with a maximum flow rate 9600 bits / s, and 1/6 th with a maximum throughput of

4800 bits / s, and so on.

  Here is the circuit 3 of communication management

  performs the simulation For this purpose, it calculates per-

  the value of an NT variable representative of the number

  total of bits stored in the buffer of the receiver.

  In order to simulate the filling of this buffer, the circuit 3 adds, as soon as a pixel line is coded and must be transmitted, the number of coding bits of this buffer.

  line to the NT variable Simultaneously, the circuit 3 memo

  increase the number of bits in this line.

  To simulate the emptying of the buffer, circuit 3 subtracts periodically, and with a period here equal to

  ms which is the duration of printing of a line by the appa-

  reception, the number of bits relative to a line to be transmitted which it has memorized for the longest, being

  understood that as soon as this subtraction is done, the cir-

  cook 2 erases his memory, that is, stops memorizing

  ser, the number of bits it has just subtracted. Thus, the output of the buffer memory of the reception, of the line which was stored in it for the longest time, is well simulated. producing with

a periodicity of 10 ms.

  As soon as the number NT, calculated as this has just been

  explained, exceeds a threshold S whose value has been

  even calculated as a fraction of the value of the buffer capacity acquired during the protocol procedure, the circuit 3 controls the deceleration of the

  flow of useful information issued.

  To do this, the circuit 3 could control the modem 4, to slow down the flow, but here, it is process of

  known way, by inserting stuffing bits.

  Thus, the information transmitted remains at a fixed rate, for example 9600 bits / s, but this information includes both useful information for coding the lines of data.

  pixels, and stuffing information.

  To slow down the rate of useful information sent, the proportion of stuffing information in

the information emitted.

  Here, for example, when circuit 3 decides the slowdown

  information flow, it adds, after the coding bits of each pixel line,

  stuffing bits not conveying any information.

  Naturally, and in known manner, the receiving apparatus is arranged not to store the stuffing bits in

  the buffer memory, since these stuffing bits do not transmit

do not carry useful information.

  To decide how many stuffing bits to add to each line, circuit-3 can use the known criterion

  which consists of completing the lines whose duration of

  This criterion is less than the print time on reception, since this criterion ensures that the buffer does not overflow. FIG. 2 shows in block form the steps relating to the simulation, by the transmission apparatus,

  filling the buffer of the reception.

  First, block 101 schematizes the step of decomposing the document into a sequence of pixels,

  decomposition carried out here mainly by the provision

Analytical tool 1.

  Block 102 schematizes the coding step of each line of pixels to be transmitted, performed by the coding circuit 2. It is assumed here that the line of rank k is coded to

  using a number of bits equal to Nk.

  Block 103 schematizes the step of adding each number of bits such that Nk to the variable NT which represents the

  total number of bits in the buffer of the receiver

  This has already been reported.

killed by the circuit 3.

  Block 104 schematizes the step of storing the number of bits Nk of each pixel line, performed by the

circuit 3.

  The block 105 schematizes the step, always performed by the circuit 3, of comparing the number NT with the threshold S, calculated in response to the value of the capacity of the buffer memory of the reception, and which represents a determined fraction

of this ability.

  If the number NT is less than the threshold S, the circuit 3 immediately commands the modem 4 to transmit the N k bits.

  coding of the line of pixels of rank k, such as the diagram of

builds block 107.

  If, on the other hand, the number NT is greater than the threshold S, the circuit 3 inserts stuffing bits after the Nk coding bits of the line of pixels of rank k, as is schematized by the block 106. flow of useful information Circuit 3 passes then

  in the step shown schematically by block 107.

  FIG. 3 shows the steps relating to the simulation, by the transmission apparatus, of the emptying of the buffer memory. The block 201 schematizes an interruption of the operation of the circuit 3 shown diagrammatically in FIG. 2, interrupting which occurs periodically, here with a period of 10 ms corresponding to the duration of printing of a line by

the receiving device.

  During this interruption, the circuit 3 subtracts from the number NT the number N of coding bits of the line of rank i, which number was the one memorized for the longest time. Then, during the step shown schematically by block 203,

  circuit 3 erases the number Ni that has just been subtracted.

  In practice, and in a known manner, the circuit 3 will execute the steps 104, 202 and 203 by storing the numbers of bits such as N or Nk in a "First Input First Output" memory. FIFO 11 Next, block 204 of FIG. 3 schematizes the end of the interruption and the return to schematized operation.

in Figure 2.

  The programming circuit 3 to perform the tasks shown schematically in Figures 2 and 3 is within the reach of

  the person skilled in the art and will therefore not be further described.

  Naturally, if the invention finds an interesting application in the field of facsimile, it is however not limited to this field and can be implemented between a transmitter and a receiver of any type, when the speed of information processing useful by the receiver is limited, and that the latter

includes a buffer memory.

Claims (7)

claims   A method for transmitting, in particular facsimiles, to a reception apparatus whose rate of processing of the useful information is limited, in which the rate of the useful information transmitted in response to the realization of a condition related to the limit value of said processing speed, characterized in that, said receiving apparatus being provided with a buffer memory, the filling and emptying of said buffer memory is simulated (103, 104, 202, 203), and   the said condition is the occupation of a determin-   born from the capacity of said buffer.   The method of claim 1 applied to facsimile transmission, in which: (101) any document to be transmitted is broken down into a series of lines of pixels, each pixel line is coded (102) using elements coding bits, in a variable number from one line of pixels to the other, the number (Nk) of bits of   coding of each line to be transmitted to a variable (NT)   of the total number of bits stored in said buffer memory, in order to simulate the filling thereof, the number (Nk) of coding bits of each line to be transmitted is stored (1 o 4), subtracted from (202) periodically, with a period equal to the print time of a line by the receiving apparatus, the number (Ni) of line coding bits to be transmitted which has been stored for the longest, in order to simulate the emptying of said buffer memory, and ceasing (203) storing the number (Ni) of line coding bits to be transmitted which has just been subtracted.   Method according to one of claims 1 or 2, in   wherein: (107) fixed rate information is transmitted, said transmitted information including useful information and stuffing information, and   we increase (106) the proportion of borrow information   rage in the said information issued to slow down the   flow of useful information issued.   4 Process according to one of claims 1 to 3, in   which, during a protocol procedure preceding the transmission of the useful information, the limit value of said processing speed and the value of the   capacity of said buffer.   Transmission apparatus, in particular of facsimile apparatus, for   implementation of the method according to one of the claims   1 to 4, for transmitting faxes to a reception apparatus whose rate of processing useful information is limited, transmission apparatus comprising means for slowing down (3) the flow of the useful information in response to determination means ( 3) performing a condition related to the limit value of said processing speed, characterized in that, said receiving apparatus being provided with a buffer memory, said means for determining the fulfillment of the condition include simulation means (3) for filling and emptying said buffer memory and means for determining (3) the occupation of a given fraction of the capacity of said buffer memory. An apparatus according to claim 5, for transmitting facsimiles comprising: means (1) for decoding any document to be transmitted into a series of lines of pixels, means (2) for encoding each line of pixels using elements encoding bits, in variable number from one pixel line to another, means (3) for adding the number (Nk) of coding bits of each line to be transmitted to a variable (NT) representative of the number total of bits   stored in said buffer memory, to simulate the replacement   pleating thereof, means (3) for storing the number (Nk) of coding bits of each line to be transmitted, means (3) for periodically subtracting, with a period equal to the printing time of a line by the reception apparatus, the number (Ni) of line coding bits to be transmitted which is stored for the longest time, in order to simulate the emptying of said buffer memory, and, means (3) ) to stop storing the number (Ni) of line coding bits to be transmitted which has just been subtracted.   Apparatus according to one of claims 5 or 6, comprising   nant: means (4) for transmitting information at a rate   fixed, the said information containing information   useful information and stuffing information, and   means (3) to increase the proportion of information   jamming in said information issued for   slow down the flow of useful information.   Apparatus according to one of claims 5 to 7, comprising   means for acquiring, during a protocol procedure preceding the transmission of useful information, the limit value of said processing speed and the value   the capacity of said buffer.