FR2753827A1 - METHOD FOR ADDING TO A SOUND SIGNAL COMPLEMENTARY INFORMATION CODE, ESPECIALLY TEXTUAL, INTENDED TO BE VISUALIZED - Google Patents

Abstract

The musical data of a sound sequence are coded in the form of series of digital samples. The complementary data, in particular textual are coded to be displayed in synchronism with the unwinding of the sound sequence. The method consists in breaking down the complementary data into digitally coded elements and mixing the digitally coded elements with the binary samples as they appear in the music sequence, so as to generate a mixed sequence of samples comprising both the musical data and the complementary data. The invention is applicable in particular to sound sequences coded according to the MIDI (Musical Instrument Digital Interface) standard. The invention also concerns a display device for displaying the complementary data. It comprises in particular a microprocessor (5) and a display screen (13) and is connected in a MIDI musical installation by means of a common bus (2) on which the samples pass through.

Description

 The present invention relates to a method for adding to a sound signal representing a musical sequence the complementary textual or musical information to be displayed during the execution of the musical sequence. Information of this nature may be, but is not necessarily, a text on which the musical sequence is written.

 According to EP 0 675 666, it is known to scroll on a display screen of a device in the form of a microphone, the lyrics and music of a song that a performer is supposed to be singing accompanied by a musical sequence that is reproduced by means of a sound installation operating according to the well known standard called MIDI (acronym for "Musical Instrument Digital Interface").

 The device or microphone is equipped with one or more memories in which are previously stored the lyrics or other musical information necessary for the execution. During this execution, the accompanying MIDI music sequence is played back while the lyrics and other additional information are extracted from the ROM (s) at the rhythm of the MIDI sync signal and displayed on the microphone display.

 This system of musical and textual reproduction has little flexibility because all of the textual information must be prerecorded in large capacity ROMs to be incorporated or possibly specially added by plugging into the microphone.

 According to another document, namely EP 0 503 978, there is known a method of creating mixed recordings, for example on compact disc, of sound sequences and textual sequences, by which the textual sequence is coded in the form a video signal that is played back and displayed simultaneously with the sound sequence. This method has the same rigidity of use as the known apparatus of the document analyzed previously.

 The aim of the invention is to propose a method for forming recordings comprising musical sequences accompanied by additional information relating to these musical sequences in order to display them during the execution of the musical sequences, recordings which require, at the level of the reproduction, a capacity The memory capacity is very small compared to the storage capacity that was required in the prior art methods.

 The subject of the invention is therefore a method of encoding information complementary to the musical information of a coded sound sequence in the form of a series of digital samples, in particular additional textual information on which said sound sequence is written, in to allow the display of said complementary information in synchronism with the course of said sound sequence, characterized in that it consists in decomposing said complementary information into digitally encoded elements and in mixing said digitally coded elements with the binary samples as and when their appearance in said musical sequence, so as to generate a mixed sequence of samples comprising both said musical information and said additional information.

 Thanks to these characteristics, a sound sequence formed using the method of the invention itself consists of a mixture of coded samples representing, in the order in which they must be restored, both the information purely musical scores relating to the score as textual or other information. This has the consequence that all the information is intrinsically synchronized with each other, the restitution material receiving them as and when the sequence of sound. Thus, the device responsible for displaying the additional information does not need a large capacity memory because the samples can be processed immediately after appearing in the sound sequence. As a result, a simple record of the length of a sample is sufficient to allow this treatment.

 In addition, since the complementary information is inserted into the ambient musical message that retains its usual form of music file, the return of this message is not disturbed by the presence of the additional information.

 The invention also relates to a recording medium on which is recorded a sound sequence obtained by the method as defined above.

The invention furthermore relates to a device for displaying complementary information contained in a mixed sequence obtained by the method as defined below, characterized in that it comprises
extraction means for extracting from said mixed sequence the coded samples comprising said digitally coded elements;
storage means connected to said extraction means for temporarily storing the extracted samples;
processing means for processing the stored samples in order to separate the digitally encoded elements from the samples;
and display means connected to said processing means for displaying the coded elements thus separated.

Other features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the appended drawings in which:
FIG. 1 is a diagram representing a sample or message according to the MIDI standard;
FIG. 2 shows an example of a time shift between musical information and complementary textual information that can be implemented in the method and the device according to the invention;
FIG. 3 is a simplified diagram of a sound reproduction installation equipped with a device making it possible to display the complementary coded information according to the invention;
FIGS. 4 and 5 are two flowcharts illustrating the operation of the display device according to the invention, flowcharts which describe two interrupt loops executed in this device.

 Figure 1 represents for memory a message according to the MIDI standard which, in the context of the present invention, can be likened to what is called a "sample".

To find a detailed description of the MIDI standard and the signals it implies, we can refer to the work of Jean-Jacques Quinet published in 1990 in "Les
Files of the ECMA ", published in Brussels by the author.

 As shown in FIG. 1, a MIDI message or sample E is generally composed of three bytes, namely one status byte S and two bytes of data D1 and D2. Some messages may only include the S status byte, others an S status byte and a single byte of data.

 Each byte is framed by a start bit BD (Start) at level "0" and an end bit BF (STOP) at level "1", the start bit BD being followed by the least significant bit of the byte that follows it. A MIDI sequence is composed of a plurality of these messages or samples following each other in time. It will be noted that status byte S always has a bit of greater weight (bit 7 in FIG. 1) at level "1" serving to identify it. Similarly for the identification of a data byte (D1 or D2), the largest bit has the level "0". The other bits of each byte contain significant information relating to the MIDI sequence to be transmitted. These bits are therefore selectively at the level "1" or at the level "0".

 It should be noted that in Figure 1, it is assumed that the time scale is increasing from left to right, the left-most bit being the one that appears first in the MIDI sequence. The arrow F indicates the direction of presentation in the sequence.

 The status byte S is divided into two parts. The four least significant bits refer to a "channel" which in a MIDI music installation corresponds to the designation of a given device and / or instrument from a number of participating instruments and / or instruments at the execution of the MIDI sequence. There can therefore be a maximum of sixteen separate devices and / or instruments in such an installation. A sample E is only taken into account by a device of the installation if the status byte S has the corresponding channel number in it.

The MIDI standard provides that three bits of the four most significant bits of the S status byte can encode eight types of commands, such as for example "Note On", "Note
Off "etc. and also a command type announcing that the first data byte of the message or sample under consideration defines a particular command called" controller "in the MIDI language.This command type is identified by the binary number" 1011 "or" B "in hexadecimal notation.

 In a sample whose status byte has this type of command "B", the data byte D1 can thus code 128 of these "controllers". Most of these have a particular assignment rigidly defined by the MIDI standard; others may be freely assigned by users to particular orders.

 According to the invention, at least one of the free controllers encodes the fact that the second data byte D2 of a MIDI sample is a binary value translating a sign belonging to information complementary to the MIDI musical sequence. itself, this information being either textual or musical, for example information that assists the performer or performers during the reproduction of the musical sequence, or a control signal that can define particular properties of displaying the additional information in question.

 Thus, if, by way of example, the data byte D1 defines a controller used for the textual complementary information, it can carry the n054 (38 in hexadecimal); the MIDI sample according to the invention then has the following form (in hexadecimal): ([x] [B1. [38]. [dd]) in which x is the channel assigned to the complementary information display device and dd the value of the alphanumeric sign belonging to this complementary textual information.

 An essential characteristic of the method according to the invention thus consists in decomposing the complementary information to a musical MIDI sequence into distinct pieces of information which are "translated" according to the MIDI standard and embedded in the musical MIDI sequence itself. Thus, if the complementary information is textual, the latter is "spelled" and each alphanumeric sign of a text is translated into a binary code which is embedded in the data byte D2 of certain samples of the MIDI sequence, a sample thus constituted being in turn embedded in the sequence of messages or MIDI samples representing the actual musical information.

 To illustrate this concept of the invention, we will examine a simple example based on the melody and the lyrics of the children's song "In the moonlight, my friend Pierrot", the melodic score of the first section of the phrase "Au clair de the moon "being shown in Figure 2.

 In the example, the coding of the text information is done according to the ASCII code; however, those skilled in the art will understand that other coding systems may also be suitable.

The type of ASCII coding gives for said first section of sentence the following sequence of MIDI samples:
{[x] [B]. [38]. [41]} = 'A'
{[x] [B]. [38]. [75]} = 'u' ([x] [B]. [38]. [20]) = '
{[x] [B]. [38]. [63]} = 'c'
{[x] [B]. [38]. [6B]} = '1'
([x] [B]. [38]. [61]) = 'a'
([x] [B]. [38]. [69]) = 'i'
[x] [B]. [38]. [72]] = 'r'
([x] [B]. [38]. (20]) =
etc ....

([x] [B]. [38]. [2C]) = 1,
It has already been clarified that the complementary information may also be of musical order, the samples relating thereto always having a status byte of value xB, but having a controller of a value different from 38 chosen from among the free controllers defined by the MIDI standard. This information may be, for example a metronome top displayed at appropriate times during the performance of the musical performance. Other samples comprising other controllers may contain chord information, information on how to present the melody written on the viewed lyrics etc.

As already mentioned, the display of the complementary information can be controlled by commands contained in the data bytes D1 and D2 of certain samples of the MIDI sequence. These so-called "control" samples can lead to the fulfillment of the following functions, the list not being exhaustive:
- Memorize a text character to display,
- Display the memorized text before the moment it
must be sung, (offset dT)
- Display a text character,
- Highlight a portion of text displayed at the moment
where she must be sung,
- Show a tone according to a table
stored in ROM,
- Display in advance a character identifying a
agreement,
- Display an entire chord when it has to
to be reproduced,
- Display a metronome symbol at a time
appropriate,
- Redefining the drawing of a character following a
matrix seven times five points,
- Assign to a character a drawing of a matrix
stored in ROM,
- Indicate, by an address of a conversion table,
in which language a tone must be displayed,
- Change the display and operation mode
information that will arrive later, - etc.

 It can thus be seen that some of these commands involve operations affecting the display of text information, while others make it possible to control the display of musical information, such as a chord, the rhythm or the like, assisting a performer in the reproduction of the musical sequence proper.

 Reference will now be made to FIG. 3 which very schematically represents a MIDI-type musical performance installation incorporating a display device and making it possible to interpret a coded musical sequence according to the method of the invention. The display device is designated by the general reference 1.

 In the embodiment shown, it has been assumed that it is a musical performance installation involving a synthesizer I (known per se) adapted to electronically restore the musical information of a MIDI sequence; this synthesizer is connected to an HP speaker.

 The installation also comprises an LC source reader, formed for example by a personal computer capable of reading a recording medium containing a MIDI sequence file recorded according to the method of the invention, for example on a flexible floppy disk which is commonly found on the market. The signals of the MIDI sequence read by the LC player pass on a common bus 2 of conventional design in MIDI technique, bus which is also connected to the display device 1 and a MIDI microphone M.

 In the example described, the display device 1 is intended to assist one or more performers, for example a singer or a choir whose synthesizer I provides the accompaniment. Thus, this or these executors can by observing the display device 1, read the text on which the musical work was written, and during the execution of the accompaniment performed by the synthesizer I. It (s) ) may also receive other additional information relating for example to instructions of harmony, counterpoint or nuances, a visual rhythm, etc.

 The display device 1 comprises a MIDI input 3 (called "IN" in the MIDI terminology) and connected to the common bus 2. This input is connected to a standard MIDI interface 4 including an opto-coupler and communicating with a microprocessor 5. This may be of the type 80C31 for example and it is connected to a memory symbolized here by a single block 6. This memory includes sections ROM and RAM. One of these sections 7 contains the microprocessor work program 5. Another section is an essential register for the present invention, since it is intended to successively store the samples of the MIDI sequence identified in their status byte by the hexadecimal number. "B". Each sample thus retained by the microprocessor 5 is processed immediately and then replaced by the next sample marked with the number "B".

It is thus seen that the samples of complementary information are not accumulated in the display device 1 prior to the execution of a musical work, but instead processed as they appear in the MIDI sequence. The display device 1 does not have to be equipped with a large memory.

 The memory 6 also comprises a buffer section 9 called line display, and several sections 10, 11 and 12 forming tables whose purpose will appear later.

 The microprocessor 5 is also connected to a display screen 13 via a directional bus 14.

In the example described here, the display screen is capable of displaying two superposed lines of text 13a and 13b of 40 characters each. A liquid crystal display or any other known type of screen may be suitable.

 The display device also comprises a switching converter 15 for supplying its various components to a voltage of 5V, for example from a 9V battery connected to a terminal 16. Of course, other power modes are possible.

The display device 1 can take many forms. For example, it can be housed in a housing adaptable to a microphone stand, be installed on a lectern or on a musical instrument etc. But, it can also be realized in other forms like for example
- a retro-projection device, which can be included in a personal headset, in transparency on the user's direct eye, or in stereoscopic proximity projection (isolated "virtual" representation)
- a video projector, a CRT or a television;
- A flat screen matrix type, monochrome or color, such as those that equip most computers called "portable".

 Note that the display device can be connected to the bus 2 by a wired link, radio or the like.

 During the execution of the musical work, all the samples of the MIDI sequence traveling on the bus 2 are applied to the input 3. The microprocessor 5 selects only the samples whose status byte includes the channel code which in the installation is assigned to the display device 1 and the code B identifying that it is a sample relating to the complementary information. It should be noted that the channel assignment can also be made by default for example on channel 16.

 The samples selected by the microprocessor 5 are temporarily stored in the register 8. It will be recalled that, according to an important characteristic of the invention, the latter retains a given sample only during the time required for its analysis by the microprocessor 5. It is then immediately replaced by the next sample and so on. It is thus seen that it is not necessary to store all the complementary information beforehand, nor to reproduce it by means of any synchronization mechanism, the synchronization according to the invention being carried out automatically by the only temporal relation that the "musical" samples and the "complementary information" samples have in the continuation of the mixed MIDI sequence.

 The analysis made by the microprocessor 5 consists first of storing the data byte (s) D1 and D2 in order to allow their subsequent processing or their appropriate application to one of the units which are connected to the microprocessor 5.

 Thus, if the controller of the byte D2 corresponds to a display command of an alphanumeric sign (38 in the example), the byte D2 which then contains the corresponding ASCII code, is routed to the buffer memory 9.

 We will now examine how the samples relating respectively to musical information and complementary information are nested within each other, with the help of the example already stated above.

This description assumes that, as shown in FIG. 3, the display screen comprises two lines 13a and 13b called respectively the high line LH and the low line.
LB. It will be seen that this display mode allows a performer to more easily anticipate the text he has to sing during the musical performance. The two lines of the display screen 13 correspond to two subsections 9a and 9b of the buffer section 9.

 The MIDI sequence sent by the source player LC first sends the first sentence of the song the samples being encoded as already indicated above.

Thus, the display device receives the following signals, Txx denoting the successive times of reception:

<tb><SEP> T00 <SEP>: <SEP> ...
<Tb>

T01 <SEP>: <SEP> A <SEP> ...
<Tb>

T02 <SEP>: <SEP> A <SEP> u <SEP> ...
<Tb>

T03 <SEP>: <SEP> A <SEP> u <SEP> ...
<Tb>

T04 <SEP>: <SEP> A <SEP> u <SEP> c <SEP> ...
<Tb>

T05 <SEP>: <SEP> A <SEP> u <SEP> c <SEP> l <SEP> ...
<Tb>

TOn <SEP>: <SEP> (lAlul <SEP> Icillalilrl <SEP> I <SEP> ... <SEP> I <SEP> lalmlii <SEP> P <SEP> i <SEP> e <SEP> r <SEP > r <SEP> o <SEP> t <SEP>, <SEP>
<Tb>
This textual information is stored in the low sub-section 9b of the buffer 9 on an order contained in the sample immediately following that ((x] [B]. [38]. [2C])) coding the comma after the word "Pierrot" . It can be the sample {[x] [B]. [38]. [OD]}, where OD is the ASCII code for "carriage return". Depending on the display mode chosen, this order may also result in the actual display on line 13b of screen 13, as follows :.

T0p: ... = (high line)
A uclair ... friend P ierrot, = (low line)
The MIDI sequence sent by the source player
LC now contains the second sentence of the song:
Let me tell you what you want!
This set of samples is followed by a control sample of the form C [x] [B]. [16]. [Cs]) allowing verification of the information that has just arrived. More specifically, it is interpreted by the microprocessor 5 to check whether the number of signs received for the first sentence is correct, the code 16 being the controller urging the microprocessor 5 to perform the verification and the code cs representing the hexadecimal number of these signs (check called "CHECK-SUM"). The verification having had the desired result, the microprocessor 5 controls the display of the sentence in high line 13a on the screen 13.

 The next sample is encoded ([x] [B]. [38]. [OD]) which causes the storage order of the second sentence just sent.

In the display mode described here, it is assumed that the performer is assisted in the interpretation by seeing displayed on the low line 13b of the screen 13 the syllable he has to sing on a given note. For this purpose, the received sequence now comprises a control sample of the form ([x] [B]. [3F]. [03]), the code 3F being the controller causing the display of the syllable and the number 03 coding the number of signs to display for this syllable (a space between the words included). This returns to the following representation on the screen:
T0s1: IAlul Icillalilrl I ... I lalmlil IPIilelrlrloltl, l = (gnehaiie)
| A | u | ~ | ~ | ~ | ~ | ~ | ~ | ... | ~ | ~ | ~ | ~ | ~ | ~ | ~ | ~ | ~ | ~ | ~ | ~ | ~ | = (low line)
The MIDI sequence now contains a sample of pure musical information representing the first note of the song that is an "OD" (see Figure 2). This sample can be of the form {[x] [9]. [48]. [40]}. In this sample x represents the channel of the synthesizer I, 9, the command "NOTE ON", 48 the note number corresponding to the pitch of the "DO" envisaged and 40 the velocity code, according to the well-known criteria of the MIDI standard. . This sample is followed by the sample of the form ([x] [8]. [48]. [7F1) where x is again the channel code of the synthesizer I, 8 the code of "NOTE OFF", 48 recall of the number of the note to which reference is made and 7F the maximum velocity code, as prescribed by the MIDI standard. This results in the rendering of the "DO" of the first note of the melody while at the same time the performer sees highlighted on the second line 13b of the display, the syllable "AU" he has to sing on this note.

The next sample is again a highlighting command of the form ([x] [B]. [3F]. [06]), the code 06 representing the number of letters of the word "CLEAR" of the first sentence of the song (including a space between the words). The display becomes:
T0s2: A uclair ... friend P ierrot, = (high line)
clear ... = (low line)
The following sample is of the form {[x] [9]. [48]. [40]} which causes the synthesizer I to restore the second "DO" of the melody (Figure 2), followed by the sample of the form {[x] [8]. [48]. [7F]} which cuts the reproduction of this second note.

The process continues in this way to allow the first sentence of the song to proceed, the last displays with which the notes of the score are synchronized automatically, being successively the following:
T0sw: A uclair ... friend P ierrot, = (high line)
... a = (low line)
T0sx: A uclair ... friend P ierrot, = (high line)
... mi = (low line)
T0sy: A uclair ... friend P ierrot, = (high line)
... P ier = (low line)
T0sz: A uclair ... friend P ierrot, = (high line)
... rot, = (low line)
While displaying the last syllable of the first sentence, a sample of the form {[x] [B]. [16]. [cs]} may cause the next sentence to be displayed in a high line and initialization of the display of the first syllable highlighted for the execution of the second sentence of the song at the low line 13b, and so right now.

The time spacing of the samples in the sequence
MIDI is provided in the usual way using the required number of time units based on a time base of the installation, depending on the rhythm chosen for the song.

 According to a particular characteristic of the invention illustrated in FIG. 2, the syllabic display of the lyrics of the song can be done in anticipation of a certain delay AT preceding the execution of the note (s) on which these syllables are written. This delay is generated by a simple shift, upstream in time, of the textual samples compared to the musical samples.

This offset can easily be determined at the time of writing the MIDI file representing the sequence in question here. Such a delay greatly facilitates reading for the performer who will then not only have at his disposal the total sentence to be sung, but also, in anticipation the syllable corresponding to the note that will be heard, after expiration of the delay AT and this successively for any syllable associated with this note.

 It has been stated above that, in practice, all samples other than those identified by an encoded S status byte x B are ignored when selected by microprocessor 5. However, an exception to this rule can be made for samples called Sys-Ex in the MIDI terminology (for System Exclusive Messages) and more specifically for those identifying the resets and pauses which are commands well known in MIDI technology; all other Sys-Ex samples are ignored until the end byte [F7] is received.

 It has also been seen that the mixed MIDI sequence according to the invention can comprise control samples resulting in the display of complementary information of musical order, as collectively called from the tables 10, 11 and 12 of the memory 6, to following receipt of these command samples, the tables may contain subroutines to ensure the display of this information. Thus, the table 10 can store information about the agreements, the table 11 can be a language conversion table for the display of comments in given languages and the table 12 could contain commands or sets of commands to ensure the display information in certain modes given.

 Since the display device 1 stores in memory (register 8) no more than one sample composed at most three bytes, another important advantage of the invention lies in the fact that the control samples carrying control signals of various functions can be nested within each other.

Since some of its functions can not be executed at the same time, a command priority system can be defined in the program managing the microprocessor 5 so that the control signals can be processed as needed. This particularity due to the invention makes it possible to further increase the flexibility that is available in the writing of a mixed MIDI sequence.

 When the display device 1 is initialized, it is placed by default in a given configuration in particular as regards the language of the display (unit 11) and the display mode (unit 12). This configuration may be modified either by particular samples of the MIDI sequence, or possibly by manual control using a control button 17 provided on the display device 1 and connected to the microprocessor 5.

 The program executed by the microprocessor 5 comprises a main loop which has to perform only two tasks namely on the one hand the refreshing of the display on the screen 13 as a function of the commands received from the samples and the mode of operation. selected operation, and on the other hand the execution of mode change orders (such as karaoke or songpad mode, for example).

 FIGS. 4 and 5 show two interrupt loops on which the main loop deviates, on the one hand, for displaying and, on the other hand, for processing samples in which byte D1 encodes a controller governing the particular control functions as described above.

 A first interruption loop of the main loop of the program is shown in FIG.

This interruption loop mainly concerns the display provided by the display device 1.

 After the initialization (step B1) of the display device 1, the microprocessor 5 expects in step B2 the MIDI sample {[x] [B]. [7A] [00]} which is adapted to control the reset of various components of the display device 1, in particular the erasing of the display buffer 9 and therefore of the screen 13, the deletion of the metronome sign, erasing the tone sign etc.

 The microprocessor 5 then waits in step B3, the sample of the MIDI sequence identifying a possible priority message. The latter may consist of a text displayed before the performance of the musical work begins. For example, the message may indicate the author of the work, the title, the copyright notice, etc. If such a sample is received, the microprocessor waits for the following samples translating, for example in ASCII code, the alphanumeric signs of the message which are stored in the buffer memory 9 in step B4.

 After this storage, the subroutine loopback on the B3 operation whose test this time receives a negative response. The loop then proceeds to the next test (step B5) to recognize the sample identifying the display command on line 13a of the display. In case of arrival of the corresponding sample, the program goes back to step B4 and returns tests B3 and B5.

These receiving a negative response, a sample is expected (test B6) identifying a display command on the low line 13b of the display screen 13. If so, the routine returns to step B4 after which tests B3, B5 and B6 are executed again. If they all receive a negative response, the routine proceeds to test B7, to identify a sample corresponding to the syllable highlighting command on screen 13. If such a sample is identified, the subroutine passes to a calculation operation (step B8) of the abscissa of the screen 13 at which the highlighting is to begin. The information thus produced is sent to buffer 9 for processing by operation B4. At the end of this operation, the routine goes back through operations B3 and B5 to B7 and if all these steps receive a negative response, a test is performed (step B9) to identify a control sample causing a reset. to zero of the organs of the display device 1. The subroutine loops back on the operation
B3, if this test proves to be negative, otherwise it loops back to the operation B2.

FIG. 5 represents another interrupt loop or subroutine that allows the microprocessor 5 to process the data contained in the data bytes D2 of the samples as naturally as these samples have a status byte identified by the hexadecimal number
B.

 This routine starts in Bill, when the microprocessor detects a first sample containing the code of a text sign to display. A first test is then performed (step B12) to check if a sequence of signs is not already being processed. If so, the data of the D2 bytes of the next samples of the incoming sequence are stored in a working buffer belonging to the RAM 7 of the microprocessor 5 (step B13). Otherwise, a new test is performed at B14 to detect a display order. If such an order is received, the routine is reconnected to the main loop by step B15. Otherwise, the routine performs a test (step B16) to identify a sample having a command controller. If so, the controller is stored by the microprocessor 5 for further processing (step B17).

 Otherwise, the routine proceeds to a B18 test to identify a reset sample. If this is detected, the main loop is informed in B19. Otherwise, the subroutine returns to the main loop at B20.

Moreover, the steps B13, B15, B17 and B19 all result in a loopback on the main loop of the microprocessor program 5.

 The invention is not limited solely to a method of encoding musical sequences mixed with complementary information according to the MIDI standard as just described.

 Indeed, the method according to the invention can also be applied in the case of music sequences encoded according to digital audio methods in which digital samples are taken successively from an analog sound sequence, as is now very widely used for the discs. compact audio.

 In this case, the method of the invention consists in replacing one of the bits of each sample, for example the least significant bit by a bit of a binary signal representing a digital fraction of the coding value of the signs. to display.

Thus, taking as an example the famous canon "Frères Jacques" the first letter of the word "Brother" could be coded as follows (F in ASCII code = 01000110):
Audio sequence {F} mixed sequence remarks [80] = 11000000 o 11000000 = [80] identity [84] = 11000100 1 11000101 = [85] difference [96] = 11010110 0 11010110 = [96] identity [A1] = 10100001 0 10100000 = [AO] difference [9F] = 10011111 0 10011110 = [9E] difference [89] = 10001001 1 10001001 = [89] identity [6C] = 01111100 1 01111101 = [6D] difference [7F] = 01111111 0 01111110 = [7E] difference
We see that this way of coding only affects very little the listening quality of the sound sequence. Thus, it can be demonstrated that for a sampling frequency of 44.1 kHz which is usual for stereophonic compact discs, the signal degradation rate is only 0.0002% which is negligible.

 A display device for capturing the information thus coded and displaying it on a screen will be designed to apply the least significant bit of the binary samples to a decoder capable of controlling a display using the successive bits detected in a the sampling signal of the sound sequence.

Claims (11)

 1. A method of encoding information complementary to the musical information of a coded sound sequence in the form of a series of digital samples, in particular additional textual information on which said sound sequence is written, in order to allow the visualization said complementary information in synchronism with the progress of said sound sequence, characterized in that it consists in decomposing said complementary information into digitally encoded elements and in mixing said digitally encoded elements with the binary samples as they appear in said musical sequence, so as to generate a mixed sequence of samples comprising both said musical information and said complementary information.  2. A process according to claim 1, characterized in that said sound sequence is coded according to the standard MIDI and in that said digitally encoded elements are embedded in MIDI samples which are mixed with the MIDI samples encoding said sound sequence.  3. A method according to claim 2, characterized in that each of said digitally encoded elements forms at least one byte of data of a MIDI sample.  4. A method according to any of claims 2 and 3, characterized in that each MIDI sample incorporating a digitally encoded element has a status byte in which the control portion encodes a controller appearing in a data byte of that sample. .  5. A method according to claim 4, characterized in that said control part comprises the hexadecimal number "B" as a high-order half-byte.  6. A method according to claim 1 characterized in that said sound sequence is encoded according to the digital audio standard compact discs and in that said digitally encoded elements are decomposed into their elementary bits which, when coding replace respectively at least one bit of low weight samples of said sound sequence, said elementary bits of each digitally encoded element being successively distributed in successive samples of said sound sequence.  7. A method according to any one of claims 1 to 6, characterized in that said additional information is of textual order and encoded according to the alphanumeric coding standard called ASCII in the second bytes of data samples.  8. A process according to any one of claims 1 to 7, characterized in that said additional information is musical and / or visualization commands.  9. A method according to claim 8, characterized in that it consists in encoding additional information relating to operations selected from the following operations:  - Memorize a text character to display,  - Display the memorized text before the moment it  must be sung,  - Display a text character,  - Highlight a portion of text displayed at the moment  where she must be sung,  - Show a tone,  - Display in advance a character identifying a  agreement,  - Display an entire chord when it has to  to be reproduced,  - Display a metronome symbol at a time  appropriate,  - Redefining the drawing of a character following a  matrix seven times five points,  - Assign to a character a drawing of a matrix  stored,  - Indicate, by an address of a table of  conversion, in which language should be displayed a  tone, and / or  - Change the display and operation mode  information that will arrive later.  10. A method according to any one of claims 1 to 9, characterized in that said digitally encoded elements are inserted temporally into said sound sequence downstream of the musical information of which it is composed.  11. A device for displaying complementary information contained in a mixed sequence obtained by the method according to any one of the preceding claims, characterized in that it comprises  extraction means for extracting from said mixed sequence the coded samples comprising said digitally coded elements;  storage means connected to said extraction means for temporarily storing the extracted samples:  processing means for processing the stored samples in order to separate the digitally encoded elements from the samples;  and display means connected to said processing means for displaying the coded elements thus separated.