WO2007007000A2

WO2007007000A2 - Method and device for directly accessing data contained in a flow

Info

Publication number: WO2007007000A2
Application number: PCT/FR2006/050688
Authority: WO
Inventors: Pierrick Philippe; Michaël PICAUD
Original assignee: France Telecom
Priority date: 2005-07-08
Filing date: 2006-07-07
Publication date: 2007-01-18
Also published as: FR2888451A1; WO2007007000A3

Abstract

The invention concerns a method wherein an encoding device generates a flow (F2) in which a binary data (bi) is associated with each frame (Ti), said binary data representing a change of encoding parameters (PVi) used to encode the encoded data (DDCi) contained in the frame associated with said binary data.

Description

Method and device for direct access to data contained in a stream.

Background of the invention

The present invention relates to the general field of the generation of a coded data stream, this stream to allow a random access to a portion of the data it contains.

The invention applies in a preferred, but not limited, manner to the broadcasting and processing of multimedia data streams (video, audio streams, etc.) in telecommunication networks.

We will now describe, with reference to FIG. _1, a known flow F1 of the type generated by an encoding system consisting of a main encoder (or "core encoder") complemented by a secondary encoder (or "extension encoder"). ").

This stream F1 is constituted by a set of successive frames T ₀ to T ₆ , each frame comprising first coded data PDC 1 obtained by the core coder, complemented by second DDQ coded data generated by the extension coder.

In a known manner, the second DDQ coded data is generated by the extension coder with variable parameters PV ₁ .

These PV variable parameters are indicated in the extension stream by means of a specific header E.

This stream F1 can be processed by a decoding system consisting mainly of a main decoder ("heart decoder") complemented by a secondary decoder ("expansion decoder").

Whenever the extension decoder detects an E header, it reconfigures itself with the new PV parameters contained in this header.

This reconfiguration is completely transparent to the main decoder who is not informed of these changes.

In the example of FIG. 1, the frames T ₀ to T ₂ contain second coded data DDCo to DDC ₂ generated by the secondary decoder with the same parameters PV ₀ . The frame T ₃ contains second coded data DDC ₃ generated with new parameters PV ₃ .

The frames T ₄ to T ₆ contain second data coded DDC ₄ to DDC ₆ generated with the same parameters PV ₃ as the second coded data DDC ₃ of the frame T ₃ .

Those skilled in the art will understand that such a stream does not make it possible to decode a set of frames which are accessed directly in the stream F2.

Indeed, assuming that it is desired to decode the frames To, Ti, T ₂ , T ₄ , there will be a problem because the extension decoder is not informed of the parameter change of the second DDGt coded data. contained in the frame T ₄ , this change of parameters was indicated in Pen-head E of the untreated frame T ₃ .

It will therefore necessarily result in a decoding error if the secondary decoder decodes the second coded data DDC ₄ of the frame T ₄ with the parameters PV ₀ unsuitable.

At best, if the secondary decoder fails to decode the second coded data DDC ₄ , it will produce a stream of digital data of lower quality, not taking into account the additional data that could have been generated by the decoding of the second data. DDQ codes of the T ₄ frame.

Object and summary of the invention

The present invention therefore has the main purpose of overcoming such disadvantages.

Thus, according to a first aspect, the invention proposes a device for coding digital data comprising:

a main coding unit adapted to generate first coded data, from these digital data; a secondary coding unit adapted to generate, according to a variable parameterization, second coded data, from the digital data complementary to the first coded data; and

a control unit adapted to generate a stream of frames, a frame comprising: first coded data; second coded data complementary to the first coded data contained in said frame; and

if the second codings contained in the frame have been generated by the secondary coding unit according to a current setting different from the parameterization used for the coding of the second coded data contained in the previous frame in the stream, a representative header of this current setting.

In a preferred embodiment, the main coding unit is an MPEG-4 AAC coder, and the secondary coding unit is an MPEG-4 SBR coder.

According to the invention, the control unit is adapted to insert, in the flow, a binary element associated with each frame of the stream, representative of the presence or absence of the header in the frame to which he is associated. According to a second aspect, the invention proposes a device for decoding coded digital data contained in a stream of frames separated by bits, a frame comprising first coded data, and second coded data, according to a variable parameterization, complementary to the first coded data. This decoding device comprises a main decoding unit adapted to generate a subset of digital data, from the first coded data and a control unit adapted to:

detecting in the stream a binary element representative of the presence, in the frame associated with this bit element in the stream, of a header comprising coding parameters of the second coded data contained in this frame; and

to implement, a secondary decoding unit adapted to generate a complement of the subset of digital data, from the second codecs contained at least in this frame. Thus, according to the invention, the coding device generates a stream in which a bit is associated with each frame, a predetermined value of this bit being representative of a change in the coding parameters used to code the second coded data. contained in the frame with which it is associated. Preferably, the control unit implements the secondary decoding unit to decode also the second coded data. contained in the frames that follow the frame associated with the binary element in the stream.

Preferably, the control unit is adapted to implement the main decoding unit following the detection of the binary element.

Thus, in a preferred use, the decoding device can be used to decode successive frames obtained by direct access to the stream. In this use, the device preferably waits, in order to begin decoding, to detect, in the stream, a binary element with a predetermined value.

This avoids using the secondary decoding unit to attempt to decode second coded data with obsolete or erroneous parameters.

In a preferred embodiment, the control unit of the coding device is adapted to control the secondary coding unit so that it inserts, in at least one frame of the stream, containing second coded data with a parameter setting identical to the one used for the coding of the second coded data contained in the frame preceding this frame in the stream, the header representative of the current setting.

This characteristic advantageously makes it possible, by increasing the frequency of the headers in the stream, to increase the level of granularity in the direct access to the parts of the data stream.

This insertion frequency can be chosen arbitrarily. The invention also provides a method for encoding digital data comprising:

a first coding step adapted to generate first coded data from the digital data;

a second coding step adapted to generate, according to a variable parameterization, second coded data, from the digital data complementary to the first coded data; and

a step of generating a stream of frames, a frame comprising:

first coded data;

second coded data complementary to the first coded data contained in the frame; and if the second codings contained in the frame have been generated according to a current parameter setting different from the parameterization used for the coding of the second coded data contained in the previous frame in the stream, a header representative of this current setting.

According to the invention, the coding method comprises a step of inserting into the stream a bit element associated with each frame of the stream, representative of the presence or absence of this header in the frame. to which he is associated. The invention also relates to a digital data stream obtained by a coding method as mentioned above.

The invention also provides a method of decoding coded digital data contained in a stream of frames separated by bits, a frame comprising first coded data, and second coded data, according to a variable parameterization, complementary to the first coded data. This process comprises:

a step of detecting, in the stream, a binary element representative of the presence, in the frame associated with this binary element in the stream, of a header comprising coding parameters of the second coded data contained in the frame; and

a first and a second decoding step respectively adapted to decode the first and second coded data contained in at least in this frame. According to a preferred implementation, the different steps of the coding method and / or the decoding method are determined by computer program instructions.

Accordingly, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a computer, this program comprising instructions adapted to the implementation of a method of encoding or decoding method as mentioned above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

The invention also relates to a computer-readable information medium, comprising instructions of a computer program as mentioned above.

The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.

On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network.

Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

Brief description of the drawings

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

FIG. 1, already described, represents a stream F1 of digital data according to the prior art;

FIG. 2 represents a stream F2 that can be generated by a coding device according to the invention and / or processed by a decoding device according to the invention;

- Figure 3 shows schematically a coding device according to the invention in a preferred embodiment;

FIG. 4 schematically represents a decoding device according to the invention; FIG. 5 represents, in flowchart form, the main steps of a coding method according to the invention;

FIG. 6 represents, in flowchart form, the main steps of a decoding method according to the invention; FIG. 7 represents, in flowchart form, the main steps of a decoding method with direct access in a stream according to the invention in another embodiment and

- Figure 8 shows schematically a computer adapted to implement a coding method and / or a decoding method according to the invention.

Detailed description of an embodiment

FIG. 2 represents a data flow F2 according to the invention in a preferred embodiment. This stream F2 comprises a set of successive frames T ₀ to T ₆ , each frame T ₁ being associated with a binary element b 1.

In the preferred embodiment described here, this association results in the fact that the binary element b, precedes the frame T, in the stream F2. A frame T, comprises:

first coded data PDC,;

second DDCi coded data, complementary to the first coded PDC data, contained in the frame T ,.

As in the prior art described with reference to FIG. 1, the second coded data DDC are coded according to a variable parameterization PV.

In the example of FIG. 1, it is considered that the first three frames T ₀ to T ₂ contain second coded data DDCo to DDC ₂ generated with the same parameters PV ₀ . It is also considered that the following four frames T ₃ to T ₆ in the stream F 2 contain second data coded DDC ₃ to DDC e generated with the same parameters PV 3 different from the parameters PV ₀ mentioned above.

The frames T ₀ and T ₃ , which are frames containing second coded data DDCo and DDC ₃ generated with new parameters PVo and PV ₃ , contain a header E representative of these parameters.

According to the invention, the binary data item bj associated with, that is to say preceding, a frame Tj in the stream F2, is representative of the presence or absence of a header E in this frame. .

Thus, the binary elements b ₀ and b ₃ comprise a binary element equal to 1 representative of the presence of the header E in the frames T ₀ and T ₃ .

According to another aspect of the invention, the frame T ₅ includes also a header E although the second encoded data DDC ₅ in this frame have been encoded with the same parameters PV ₃ the additional second data SDC ₄ the frame T ₄ preceding this frame T ₅ in the stream F2. Consequently, the binary element b ₅ associated with the frame T ₅ is equal to 1. The other binary elements b ₁ , b ₂ , b ₄ and b ₆ are all equal to

0, since they are respectively associated with a frame Ti, T ₂ , T ₄ and T ₆ whose complementary data DDQ have been coded with the same parameters as the frame T ₀ , Ti, T ₃ and T ₅ which precedes it in the F2 stream.

FIG. 3 represents a coding device 10 according to the invention in a preferred embodiment.

This coding device is adapted to implement steps E10 to E70 of a coding method according to the invention shown in FIG.

We will now describe how the coding device 10 can generate the stream F2 described above with reference to FIG. 2 for the coding of digital data D.

This coding device 10 comprises a main coding unit 12 adapted to generate, during a step ElO of the coding method according to the invention, first coded data PDQ. Thus, upon receipt of the first digital data D, this coding unit generates first PDCo coded data.

The coding device according to the invention comprises a secondary coding unit 14 adapted to generate, during a step E20, preferably substantially simultaneously at the step ElO described above, second coded data DDCo according to a variable parameterization. PV ₀ . The first coded data PDCo and the second coded data DDC ₀ are received by a control unit 16 adapted to generate, during a step E30, a frame T ₀ comprising these first coded data PDC ₀ and these second coded data DDC ₀ . The frame generation step E30 is followed by a test E40 during which the coding unit 10 determines whether the variable parameters PV ₀ used to generate the second coded data DDC0 are different from those used for the coding of second coded data. of a possible frame preceding the frame T ₀ . As is the case (the frame T ₀ is the first frame), the result of the test E40 is positive.

This test is then followed by a step E80 during which the control unit 16 assigns the value 1 to a binary element b 1, this binary element to be associated with the frame T ₀ in the stream F 2. In the embodiment described here, this association consists in placing the binary element b ₀ just in front of the frame T ₀ in the stream F2.

As a result, the bit b1 is inserted in a step E60 by the control unit 16 into the stream F2.

It will be noted that during the preceding step E80, the secondary coding unit 14 inserts a header E comprising the coding parameters PV ₀ of the second coded data DDC ₀ , in the frame T ₀ , because these PVo parameters have not been used to encode second complementary data contained in a frame preceding the frame T ₀ . The step E60 of inserting the binary element b1 in the stream F2 is followed by a step E70 of insertion of the frame To in the stream F2.

The coding device 10 continues to process digital data D thus generating (step E30) two frames Ti and T ₂ containing:

first coded data PDCi, PDC ₂ generated during the step ElO already described;

second DDCi, DDC ₂ coded data generated during a second coding step E20 already described, these first coded data and second coded data being placed in Ti and T ₂ frames during a step E30. During the test E40, the control unit 16 determines that the variable parameters used to generate the second coded data DDCi and DDC ₂ have not changed, so the result of the E40 test is negative.

This test E40 is then followed by a step E50 during which the control unit 16 assigns the value 0 to the binary elements b ₁ and b ₂ and then associates these binary elements with the frames Ti and T ₂ , by inserting these binary elements bi and b ₂ in the stream F2 during the step E60 already described, respectively just before the frames Ti and T ₂ .

Assuming that the secondary coding parameters PV vary during the generation of the frame T ₂ , the control unit 16 determines this change during the step E40 already described during the coding process of the following digital data D.

Therefore, the E40 test result is positive and the control unit 16 in step E60 inserts a bit b3 equal to 1 in the flow F2, the header E containing the novel PV ₃ parameters being inserted by secondary coding unit 14 in the frame T ₃ during the step E80.

It will be assumed later that the variable parameters PV secondary coding no longer vary.

However, in the preferred embodiment described here, the control unit 16 of the coding device 10 is adapted to send a signal Sl to the secondary coding unit 14, so that it inserts an E header in a frame T ₁ , although the second coded data DDQ contained in this frame have been generated with parameters PV ₁ identical to the second coded data DDQ-i of the previous frame T _K in the stream F2. In the preferred embodiment of this variant, when the signal Sl is active, the result of the determination test E40 is positive.

It will be assumed that the signal Sl becomes active during the generation of a frame T ₅ (step E30).

Consequently, the result of the following determination test E40 is positive and the control unit 16 assigns the value 1 to a binary element b5 (step E80), the E header with the unchanged variable parameters PV ₃ being substantially simultaneously inserted into the frame T ₅ .

The binary value b ₅ and the frame T ₅ are then inserted in the stream F2 (steps E60 and E70). We will now describe with reference to Figure 4 a decoding device 20 according to the invention in a preferred embodiment.

This decoding device 20 is adapted to implement the decoding method according to the invention, the main steps of which are given in FIG.

It will be assumed initially that this decoding device 20 receives an instruction for decoding the frames T ₂ , T ₃ , T ₄ of the stream F 2 (step F 3). On receiving a decoding instruction, a control unit 26 of the decoding device 20 sets a Flag flag to the value 1 (step F5).

The control unit 26 reposition the flag to 1 as soon as direct access is desired in the stream. This is particularly the case when one wants to access a frame that does not succeed, in the stream, the previously decoded frame.

Then, we will assume that during a waiting step FI1, the decoding device 20 receives the binary element D ₂ .

This step FI1 is followed by a step F30 during which the control unit 26 determines whether:

the bit b ₂ contained in the stream F 2 just before the frame T ₂ is representative or not of the presence of a header in the frame T ₂ . ; or if :

if the Flag flag stores the value 0. Since this is not the case, it is not possible to correctly decode the second coded data DDC ₂ of the frame T ₂ (implementation materialized in FIG. opening of the switch 25) and the step F30 is followed by the step FIl waiting for the binary element b ₃ .

During the following step F30, the control unit 26 determines that the binary element b ₃ preceding the frame T ₃ is equal to 1. This step F30 is then followed by a step FlO waiting during which the decoding device 20 receives the frame T ₃ .

On receipt of this frame, the control unit 26 transmits the frame T ₃ to a main decoding unit 22 which, during a step F20, generates a subset SSD of the digital data which was the origin of the coding into first coded data PDC3 and second coded data DDC ₃ contained in the frame T ₃ .

Step F20 is then followed by a step F40 to allow the decoding of the second complementary data DDC ₃ contained in the frame T ₃ .

To do this, the control unit 26 implements (this implementation being embodied in FIG. 4 by the closing of a switch 25) a secondary decoding unit 24 for generating a complement CP of the subset of data SSD from second complementary data DDC ₃ of the frame T ₃ .

The decoding step F40 is followed by a step F50 during which the control unit 26 sets the Flag flag to the value 0.

The step F50 is followed by the step FIl waiting for the binary element b ₄ already described. Then, in step F30, the control unit 26 determines that the Flag flag contains the value 0.

Therefore, although the binary element b ₄ preceding the frame T ₄ is zero, the step F30 is followed by the step FlO waiting already described (implementation materialized in Figure 4 by closing the switch 25).

The frame T ₄ is transmitted by the control unit 26 and then transmitted to the main decoding unit 22 to continue generating the subset of SSD data from the first coded data PDC ₄ contained in the frame T ₄ (step _4). F20). Step F20 is then followed by a step F40 to allow the decoding of the second complementary data DDC ₄ contained in the frame T ₄ .

For this purpose, the control unit 26 implements the secondary decoding unit 24 to generate a complement CP of the subset of data SSD from the second complementary data DDC ₄ of the frame T ₄ .

This step F40 is followed by a step F50 during which the flag Flag is kept at zero and the decoding device 20 returns to the step FIl waiting already described. In another decoding method according to the invention, the step

F20 main decoding is always performed and decoding secondary is only performed if the result of the F30 determination test is positive.

It is understood that the invention makes it possible, in contrast with the decoders of the state of the art, to avoid, in the aforementioned sequence of To frames, Ti, T ₂ , T ₄ , an erroneous decoding of the coded secondary data DDC ₄ of the T frame ₄ .

Indeed, because the frame T ₃ is not decoded, the control unit 26 reposition the Flag flag to the value 1 when one wants to access the frame T ₄ . Since the binary value b ₄ is zero, and the flag Flag is set to 1, when processing the frame T ₄ , the result of the test F30 is negative and the data are not decoded.

FIG. 7 represents, in flowchart form, a decoding method with direct access in an audio stream with band extension according to the invention in a second embodiment.

In this embodiment, from a frame that does not contain PV encoding parameters, the first frame that has this header back in the stream is searched for using the bit. This embodiment makes it possible to directly access a frame T _M and to restore an optimal quality, that is to say without decoding error on the secondary data of this frame T _M , and the following ones if they are accessed.

It is assumed that in step G5 a request for access to the frame TM is received.

In this embodiment, this step G5 is followed by a step Gl0 during which a variable N is initialized with the index M of this frame T _M in the stream.

Then, during a loop formed by steps G15, G20 and G30, the first frame T _N is searched in the stream for which the binary element bu is set to the value 1.

In the embodiment described here, this loop is followed by a step G35 in which the frames T _N to T _M -i are transmitted, which are decoded in step G40 without presenting them to the user, since access to these frames is not required. Finally, during a step G45, the required frame is presented, as well as, if necessary, the following frames if access to these frames is requested, as described with reference to FIG.

FIG. 8 shows a computer 100 adapted to implement an access method according to the invention, and in particular in the three embodiments previously described in FIGS. 2A to 2C.

This computer 100 comprises, in known manner, a processor 101, a ROM-type ROM 102 and a RAM RAM 103.

The processor 101, the read-only memory 102 and the random access memory 103 are connected by a bus system 104.

Claims

An apparatus (10) for encoding digital data (D) comprising: - a main coding unit (12) adapted to generate first coded data (PDC) from said digital data (D);

- a secondary coding unit (14) adapted to generate, according to a variable parameterization (PV), second coded data (DDC ₁ ), from said digital data (D), complementary to said first coded data (PDC ₁ ); and

a control unit (16) adapted to generate a frame flux (F2) (T ₁ ), a frame (T ₃ ) comprising:

- first coded data (PDC ₃ );

said second coded data (DDC ₃ ), complementary to the first coded data (PDC ₃ ) contained in said frame

(T ₃ ); and

if said second codecs (DDC ₃ ) contained in said frame (T3) were generated by said secondary coding unit (14) according to a current setting (PV ₃ ) different from the setting (PV ₀ ) used for the coding of the second data coded (DDC ₂ ) contained in the preceding frame (T ₂ ) in said stream (F2), a header (E) representative of this current setting

(PV ₃ ); the coding device (10) being characterized in that said control unit (16) is adapted to insert, in said stream (F2), a binary element (b) associated with each frame (T ₁ ) of said stream (F2 ), representative of the presence (1) or absence (0) of said header (E) in the frame (T,) with which it is associated.

2. coding device according to claim 1, characterized in that said control unit (16) is adapted to control (S) said secondary coding unit (14) so that it inserts, in at least one frame (T ₅ ) of said stream, containing second coded data (DDC ₅ ) with a setting (PV ₃ ) identical to that used for the coding of the second coded data (DDC ₄ ) contained in the frame (T ₄ ) preceding said frame (T ₅ ) in said stream (F2), said header (E) representative of said current setting (PV ₃ ).

A method of encoding digital data (D) comprising: - a first encoding step (ElO) adapted to generate first coded data (PDQ), from said digital data (D);

a second coding step (E20) adapted to generate, according to a variable parameterization (PV), second coded data (DDC ₁ ), from said digital data (D) complementary to said first coded data (PDC ₁ ); and

a step (E70) for generating a frame flux (F2) (T ₁ ), a frame (T ₃ ) comprising:

said first coded data (PDC ₃ );

said second coded data (DDC ₃ ) complementary to the first coded data (PDC ₃ ) contained in said frame

(T ₃ ); and

if said second codecs (DDC ₃ ) contained in said frame (T ₃ ) have been generated according to a current setting (PV ₃ ) different from the setting (PV ₀ ) used for the coding of the second coded data (DDC ₂ ) contained in the previous frame (T ₂ ) in said stream (F2), a header (E) representative of this current setting (PV ₃ ); said coding method comprising a step (E60) of inserting into said stream (F2) a binary element (b) associated with each frame (T ₁ ) of said stream, representative of the presence (1) or of the absence (0) of said header (E) in said frame (T ₁ ) with which it is associated.

4. Device (20) for decoding coded digital data (PDCi, DDCi) contained in a stream (F2) of frames (T,) separated by bits (b), a frame (T,) comprising first data coded (PDCi), and second coded data (DDQ), according to a variable parameterization (PV), complementary to said first coded data (PDQ), said device (20) comprising a main decoding unit (22) adapted to generate a sub-code. -Set (SSD) of digital data, from said first coded data (PDQ) and a control unit (16) adapted to: detecting in said stream (F2), a binary element (b ₃ ) representative of the presence (1), in the frame (T3) associated with said binary element (b ₃ ) in said stream (F2), of a header ( E) comprising coding parameters (PV3) of the second coded data (DDC ₃ ) contained in said frame (T ₃ ); and

to implement (S2) a secondary decoding unit (24) adapted to generate a complement (CP) of said subset (SSD) of digital data, from the second codecs (DDC ₃ ) contained at least in said frame (T ₃ ).

5. Decoding device according to claim 4, characterized in that said control unit (16) is adapted to implement (S2) said secondary decoding unit (24) to decode also the second coded data (DDC ₃ - DDCe ) contained in the frames (T ₄ - T ₆ ) following the frame (T ₃ ) associated with said binary element (b ₃ ) in the stream (F2).

6. Decoding device according to claim 4 or 5, characterized in that said control unit (16) is adapted to implement (S2) said main decoding unit (22) following the detection of said binary element (b _3). ).

7. A method for decoding coded digital data (PDQ, DDC ₁ ) contained in a stream (F2) of frames (T,) separated by bits (b), a frame (T ₁ ) comprising first coded data ( PDC ₁ ), and second coded data (DDC ₁ ), according to a variable parameterization (PV), complementary to said first coded data (PDC ₁ ), said method comprising:

a step (F30) of detecting, in said stream (F2), a binary element (b ₃ ) representative of the presence (1), in the frame (T ₃ ) associated with said binary element (b ₃ ) in said flow (F2) of a header (E) comprising coding parameters (PV3) of the second coded data (DDC ₃ ) contained in said frame (T ₃ ); and

a first (F20) and a second (F40) decoding step respectively adapted to decode first (PDC ₃ - PDC ₆ ) and second (DDC ₃ - DDCβ) coded data contained at least in said frame (T ₃ ).

8. Flow (F2) of digital data obtained by an encoding method according to claim 3.

Computer program comprising instructions for performing the steps of the encoding method according to claim 3, or steps of the decoding method according to claim 7 when said program is executed by a computer.

A computer-readable recording medium on which a computer program is recorded including instructions for performing the steps of the encoding method according to claim 3, or steps of the decoding method according to claim 7.