Abstract:
A dictation apparatus is disclosed for storing a speech signal in a memory. The dictation apparatus includes a data compression unit for compressing the speech signal and a storing unit for storing the data compressed speech signal in the memory. The data compression unit performs the data compression on the speech signal in one of at least two different selectable data compression modes. The data compression unit also creates data files including portions of the data compressed speech signal and a header portion including an identifier signal identifying the data compression mode selected. For realizing an insert, a control unit is included that is selectively operable by a user for providing an insert signal and an end of insert signal. In response to the occurrence of each insert signal, a block of at least two and at most three pointing vectors is generated. The block of pointing vectors include a first address signal corresponding to the address where the dictation insert should be placed and a second address signal corresponding to a beginning address of an available portion of said addressable memory for storing the dictation insert.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a dictation apparatus for storing a speech signal in addressable memory means and to a transcription apparatus for transcribing speech messages. A dictation apparatus as defined in the opening paragraph is well known in the art. Reference is made in this respect to EP-A 65,148, document (4) in the list of related documents. 
     Data compression may be realized in prior art dictation apparatuses by discarding the silence periods normally present in the speech signal. Further, one may store an indication signal indicating the length of the silence period and its location in the speech signal. Upon transcription, a replica of the speech signal can be regenerated by inserting silence periods of the same length at the indicated positions in the compressed speech signal. 
     Sometimes an insert need to be added to a speech signal stored earlier in the memory means. EP-A 65,148 describes a way how to enable an insert to be stored in the memory means. 
     SUMMARY OF THE INVENTION 
     The invention aims at providing an improved dictation apparatus. The dictation apparatus in accordance with the invention is characterized in that the device comprising 
     input means for receiving the speech signal, 
     data compression means for data compressing the speech signal into a data compressed speech signal, the data compression means being adapted to carry out a data compression step on the speech signal in one of at least two different data compression modes, the at least two different data compression modes resulting in different data compression ratios when applied to the same speech signal, the said at least two different data compression modes being selectable by a user, the data compression means being further adapted to create data files comprising a data compressed speech signal, the data files comprising a header portion, the data compression means being also adapted to generate an identifier signal identifying the data compression mode selected and being adapted to store said identifier signal in said header portion, 
     storing means for storing the data files in the memory means, the storing means comprising address generator means for generating addresses for said addressable memory means, for storing blocks of information comprised in a data file in the memory means, 
     control means selectively operable by a user for providing an insert signal and an end of insert signal, 
     pointing vector generator means for generating a block of at least two and at most three pointing vectors in response to the occurrence of each insert signal, said block of pointing vectors comprising a first address signal corresponding to the address generated by the address generator means upon the occurrence of the insert signal and a second address signal corresponding to a beginning address of an available portion of said addressable memory for storing a dictation insert. 
     The invention is based on the following recognition. The memory capacity of memories included in dictation apparatuses is limited. Preferably, an increased number of dictations should be stored in a memory. This has been realized in the prior art by leaving out the silence periods present in a speech signal. A larger compression ratio can be obtained by applying more powerful compression techniques. More specifically, lossy compression techniques result in large data compression ratios. Larger data reduction ratios, however, may lead to a decrease in quality of the retrieved signal upon data expansion. In accordance with the invention, a dictation system has been proposed in which the user has the possibility to choose one data compression mode from two or more data compression modes in which the dictation apparatus can compress the speech signal. The user can make a trade off between the number of speech messages that he wants to dictate and store in one memory unit and the quality of the speech signal upon reproduction. If the user wants to have more dictations stored in the memory, he will select the data compression mode giving a higher data compression ratio. If the user prefers a higher quality of reproduction, he will choose the data compression mode giving a lower data compression ratio. 
     Further, storing an insert in the memory means is realized by storing two, or in another embodiment, three pointing vectors at the maximum for each insert to be stored in the memory means. This has an advantage over the prior art dictation apparatus, which requires the storage of a jump signal at the location in the originally stored speech signal where the insert should be made, thereby overwriting a portion of the original speech signal stored, a jump signal at the end of the stored insert and four pointing vectors linking the two addresses from which a jump should take place to the two addresses where the jumps should end. 
     Contrary to this, in one embodiment of the invention, only two pointing vectors are required, linking the address in the originally stored speech signal where the insert should be made and the address corresponding to a beginning address of an available portion of said addressable memory for storing a dictation insert. At the end of the insert, an end-of-file signal could bestored, which can be used as jump instruction upon reproduction so as to jump back to the position of the insert in the original speech message. 
     In another embodiment, exactly three pointing vectors are stored in a block of pointing vectors, the third address signal corresponding to the address generated by the address generator means upon the occurrence of the end of insert signal. Upon reproduction in the transcription apparatus, the addresses generated by the address generator means are compared to the first address signal so as to activate the first jump from the location of the insert in the originally stored speech signal, which corresponds to this first address signal, towards the location where the beginning of the insert is stored, which corresponds to the second address signal, upon equality of the generated addresses with the first address signal. The addresses generated by the address generator means are further compared to the third address signal so as to activate a second jump from the location where the end of the insert is stored, which corresponds to the third address signal, towards the location of the insert in the originally stored speech signal, which corresponds to the address subsequent to the first address, upon equality of the generated addresses with the third address signal. 
     The various subclaims define preferred embodiments of the dictation apparatus and the transcription apparatus in accordance with the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects of the invention will be apparent from and elucidated further with reference to the embodiments described in the following figure description, in which 
     FIG. 1 shows an embodiment of the dictation apparatus, which is in hand held form, 
     FIG. 2 shows an embodiment of the memory card for use in an embodiment of a dictation apparatus, provided with such a removable memory card, 
     FIG. 3 shows the circuit diagram in the dictation apparatus, 
     FIG. 4 shows an embodiment of a transcription apparatus, either in table top, or in PC form, 
     FIG. 5 shows the memory unit in which the files comprising the speech signals are stored, and 
     FIG. 6 shows the storage of an insert in the memory unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a front view of a dictation apparatus in accordance with the invention, which is in this example in hand held form. The apparatus  1  provided with an on/off switch  2  located on the side of the housing of the apparatus. At the bottom of the housing a battery compartment  3  (not shown) is provided that can be reached at the back of the housing. A sliding switch  4  is provided on the front face of the housing for switching the apparatus in the various dictation modes. The apparatus is provided with a number of buttons: button  5  is the record button, button  6  is the LETTER button, button  7  is the MODE button, button  8  is the INSERT button and button  9  is the DELETE button. The switch  10  is the recording mode switch. The switch  11  is the sensitivity switch. The apparatus  1  is further provided with a LCD display for displaying various information regarding a dictation, such as the recording time of the dictation, the recording time left, the recording mode, the number of dictations, etc. 
     A microphone  13  and a loudspeaker  18  are provided in the housing and a volume control knob  14  is provided on the side of the housing. Further, a slot  16  is provided in the top face of the device for receiving a memory card  15 . 
     The memory card  15  is also shown in FIG.  2 . The memory card  15  is provided with a solid state memory  20  and with electrical terminals  22  connected to the solid state memory  20 . The solid state memory  20  can eg. be an EEPROM or a flash erasable memory. The electrical terminals  22  can be such that they enable an electrical cooperation with the internationally standardized PCMCIA interface of a PC. 
     FIG. 3 shows the electrical construction of the apparatus  1  and its cooperation with the memory card  15 . The apparatus  1  comprises a digital signal processor  30 , having a digital input/output  32  coupled to terminals  34  that are electrically coupled to the terminals  22  of the memory card  15 , when positioned in the slot  16 . The microphone  13  is coupled to an analog input  36  of the processor  30 , if required via an amplifier  38 . The processor  30  further comprises an analog output  40  which is coupled to the loudspeaker  18  via an amplifier  42 . The various knobs and buttons, denoted in FIG. 3 by the reference numeral  44  are coupled to control inputs  46  of the processor  30 . Further, a control output  48  of the processor  30  is coupled to a display control unit  50  for controlling the display of information on the display  12 . 
     The user places the memory card  15  into the slot  16  of the apparatus  1  until the terminals  22  of the memory card  15  come into contact with electrical terminals  34  provided in the slot of the device  1 . The memory card is now in electrical and mechanical contact with the apparatus  1 . 
     The processor  30  is capable of receiving the analog speech signals via the input  36  and to A/D convert the speech signal into a digital speech signal. Further, upon selection by the user, the processor  30  is capable of carrying out one of at least two different data compression steps on the digital speech signal. Suppose, the processor  30  is capable of carrying out two data compression steps on the speech signal. Each compression step carried out on the same speech signal results in different compression ratios. The data compression steps can be in the form of lossless compression steps. This means that no data is actually lost and the original speech signal can be fully recovered upon data expansion. One example of a lossless data compression method is linear predictive coding followed by a Huffman encoding carried out on the output signal of the linear predictive coder. Data compression can also be lossy. One such lossy data compression step is subband coding, well known in the art and applied in DCC digital magnetic recording systems. In lossy compression methods, part of the information that is unaudible is actually thrown away. Upon data expansion, a replica of the original speech signal is recovered. As the information that is left out upon data compression was unaudible, the replica of the speech signal will be heard by the user as being the same as the original speech signal. 
     The processor  30  may be capable of carrying out a lossless data compression step on the speech signal and a lossy data compression step, as the two different data compression steps that can be realized by the processor  30 . As an alternative, the processor  30  can carry out two different lossless data compression steps resulting in different data compression ratios. As again another alternative, the processor  30  may be capable of carrying out two different lossless data compression steps on the speech signal, resulting in two different data compression ratios. As an example of the last possibility: the processor  30  could be provided with a simple subband encoder as applied in DCC. The subband encoder can be simple as less subbands are required for encoding the speech signal. Less subbands are required, eg. 5 instead of the 32 in the DCC subband encoder, as the bandwidth of the speech signal is much smaller than a wideband audio signal. Different compression ratios can be obtained with the simplified subband encoder by changing the bitpool for the bitallocation step in the simplified subband encoder. Reference is made in this respect to the documents (1), (2), (3a) and (3b) in the list of documents that can be found at the end of this description. 
     When the user wants to record a speech message into the device, he depresses the LETTER button  6 , which indicates that the user wants to store a speech message. Further, the user can actuate the MODE button  7  in order to select various modes, such as whether the speech message should have a (high) priority, or whether the speech message should be protected from overwriting. Subsequently the user selects a recording mode by actuating the button  10 . Selecting the recording mode means that the user selects a data compression mode. If the user wants a relatively good quality recording, he/she chooses the data compression mode resulting in the lowest data compression ratio. As a result, a larger amount of information will be stored in the memory  20  for the said dictation, so that less dictations can be stored in said memory. If the user wants as many dictations as possible being stored in the memory  20 , he/she will choose the data compression mode resulting in the higher data compression ratio. A lower quality storage of the dictations may be the result. 
     The compressed information is included in blocks of information (or ‘files’) F 1 , F 2 , . . . . This is shown in FIG.  5 . Each file of information F has a header portion, denoted HDR, and an information portion, denoted IP. An identifier signal is stored in the header portion. The identifier signal in a header portion HDR of a signal block identifies the compression mode applied on the speech signal in order to generate the data compressed information stored in the information portion IP of that same signal block. The sequence of signal blocks is supplied to the digital output  32  of the processor  30  and subsequently stored in the memory  20  on the memory card  15 . The data portion of a file could be terminated by using an end-of-file codeword EOF. 
     It should be noted here, that in the present example, the processor  30  generate signal blocks as long as required to store the information of exactly one speech message in. 
     Storing of the data compressed speech signal into the memory  20  is realized by supplying the data compressed speech signal to an input  28  of the memory. Further an address generator  26  is present in the processor  30  to generate addresses for the memory  20 . Those addresses are supplied to the memory  20  via an input  24 , see the FIG.  5 . Bytes of information of the data compressed speech signal are stored at subsequent storage locations in the memory  20  by supplying subsequent addresses to the memory  20  via the input  24 . As said before, the file can be closed by storing an end-of-file word in the memory  20 . 
     Now, it will be described how an insert can be stored in the memory. Reference is made to FIG. 6, for further explanation. Suppose the user of the dictation apparatus has stored a speech message in his/her dictation apparatus as a speech file F i . Upon checking the dictation when rehearing the message, he/she considers an insert to be necessary at a certain location in the speech message. He/she presses the INSERT button  8  at the location in the stored speech message where the insert should be done. In FIG. 6, it can be seen that the insert should be added after the address n in the originally stored speech message. Upon depressing the INSERT button  8 , a block  29  of pointing vectors is generated. As a first pointing vector in the block  29 , the address n, where the insert should be added, is stored in the block  29 . Next, the signal processor looks for an empty portion in the memory  20  where the insert can be stored. In the example of FIG. 6, this empty portion is directly behind the file F i  and starts at the address p. As a second pointing vector in the block  29 , the address p, where the beginning of the insert will be stored, is added to the block  29 . Next, the signal processor  30  stores the insert in the memory  20 . Upon the termination of the storage of the insert in the memory  20 , the insert is stored in the memory locations starting with the address p, until the address q. As a third pointing vector in the block  29 , the address q, where the end of the insert is be stored, is added to the block  29 . Next, the signal processor  30  stores the block of three pointing vectors in the header portion HDR of the file F i , see FIG.  6 . 
     Especially in a situation where the memory  20  is removable from the dictation apparatus, the block of pointing vectors should be stored in the memory  20  itself. It may however be possible to store the block of pointing vectors in another location in the memory  20  than in the file header of the file itself. One could imagine a table of contents for all the files in the memory being stored in the memory  20 , and that the block of pointing vectors is stored in this table of contents. In another embodiment, the block of pointing vectors could have been stored in a memory location in the dictation apparatus which is separate from the memory  20  in which the files are stored. 
     Further, in another embodiment, the storage of the insert in the memory  20  could have been terminated by storing an end-of-file word at the end of the stored insert. In this situation, there is no real need for storing the third address in the block of pointing vectors, as will be made clear later. 
     If the user wants to hear the speech message stored in the memory  20 , the processor  30  is capable of retrieving the data compressed information from the memory  20  and carry out a data expansion step on the data compressed information stored in the memory. It will be clear that the data expansion step will be the inverse of the data compression step carried out during dictation. The data expansion step to be carried out in the processor  30  will be further explained hereafter, with respect to an embodiment of a transcription apparatus, as shown in FIG.  4 . After having obtained a replica of the speech signal, this speech signal is D/A converted in the processor and supplied to the output  40 , for reproduction by the loudspeaker  18 . 
     For transcription of the speech messages stored in the memory  20  on the memory card  15 , the memory card  15  is withdrawn from the device  1  and inserted in a table top transcription apparatus  52 , see FIG.  4 . The transcription apparatus  52  comprises a digital signal processor  53 , having a digital input  54  coupled to terminals  56  that are electrically coupled to the terminals  22  of the memory card  15 , when positioned in a slot (not shown) provided in the apparatus  52 . A loudspeaker  58  is coupled to an analog output  60  of the processor  53 , via an amplifier  62 . The processor  53  further comprises a control output  64  which is coupled to a display control unit  66  for controlling the display of information on a display  68 . A keyboard  70  is coupled to control inputs  72  of the processor  53 . 
     The user places the memory card  15  into the slot (not shown) of the transcription apparatus  52  until the terminals  22  of the memory card  15  come into contact with electrical terminals  56  provided in the slot of the transcription apparatus  52 . The memory card is now in electrical and mechanical contact with the apparatus  52 . 
     Upon actuating a ‘RETRIEVE’ button on the keyboard  70 , the information stored in the memory  20  on the memory card  15  is read out and stored in an internal memory of the digital signal processor  53 . The processor  53  is capable of carrying out one of at least two different data expansion steps on the digital information retrieved from the memory card. It will be clear that the expansion mode carried out in the processor  53  is the inverse of the compression mode carried out during the dictation step in the processor  30 . The processor  53  retrieves the identifier signal from the header portions HDR of the signal blocks and carries out a data expansion step in response to the identifier signal. As a result, a replica of the digital speech signal is obtained. 
     The processor  53  is further capable of D/A converting the replica of the digital speech signal into an analog speech signal and to supply the analog speech signal via the output  60  to the loudspeaker  58 , so that a typist or other person can hear the speech signal that need to be transcribed. 
     The typist can type in the speech message reproduced via the loudspeaker using the keyboard  70 , so as to obtain a typed version of the speech message. 
     In another embodiment of the transcription apparatus  52 , when realized in the form of a personal computer, having a sufficiently large memory capacity, the apparatus may be provided with a speech recognition algorithm which enables the apparatus to generate a character file from the speech signal as a result of such speech recognition step. The character file could be made visible on the display  68 , so that the typist can check for errors by reading the text on the display screen  68  and hearing the speech message via the loudspeaker  58 , and correct those errors using the keyboard  70 . 
     Previously an example of a lossless data compression method has been described, namely: linear predictive coding followed by a Huffman encoding. It will speak for itself that the processor  53  must be capable of carrying out a corresponding Huffman decoding followed by a corresponding linear predictive decoding in order to regenerate the original speech signal. 
     An example of a lossy data compression step has also been described, namely: subband coding. It will speak for itself that the processor  53  must be capable of carrying out a corresponding subband decoding in order to regenerate a replica of the original speech signal. 
     Now, the retrieval of the speech file and the insert shown in FIG. 6, will be explained. 
     The processor unit  53  has an address generator  26  which generates subsequent address signals for addressing subsequent storage locations in the memory  20 . For retrieving the file F i , the address generator  26  generates addresses starting with the address a and subsequent addresses until the address n. Upon retrieving the header portion HDR, the processor unit  53  is capable of retrieving the block of pointing vectors  29  from the header. The processor unit  53  further comprises a comparator  74 , schematically shown in FIG. 4, for comparing the addresses generated by the address generator  26  with addresses stored in the block of pointing vectors. First a comparison is made with the first address n stored in the block of pointing vectors. Upon detection of equality, the comparator generates a control signal which is supplied to the address generator  26 , together with the second address p in the block of pointing vectors. Upon receiving the control signal, the address generator  26  is set to the address p, and subsequently generates subsequent addresses starting from the address p. The insert can now be retrieved from the memory  20 . The comparator  74  now compares the addresses generated by the generator  26  with the third address q stored in the block of pointing vectors. Upon detection of equality, the comparator generates another control signal which is supplied to the address generator  26 . Upon receiving the control signal, the address generator  26  is set to the address n+1, and subsequently generates subsequent addresses starting from the address n+1. The remaining portion of the speech message can now be retrieved from the memory  20 . 
     In another embodiment, the end of the insert is detectable because of an end-of-file word which is stored as the last word at the location of the address q. Now, a block of pointing vectors can comprise two addresses only. Upon detection of the end-of-file word at the location q in the memory, the address generator  26  is set to the address n+1, and subsequently generates subsequent addresses starting from the address n+1. The remaining portion of the speech message can now be retrieved from the memory  20 . 
     Whilst the present invention has been described with respect to preferred embodiments thereof, it is to be understood that these are not limitative examples. Thus, various modifications may become apparent to those skilled in the art, without departing from the scope of the invention, as defined by the claims. Further, the invention lies in each and every novel feature or combination of features as herein disclosed. 
     Related Documents 
     (1) EP-A 402,973 (PHN 13.241). 
     (2) EP-A 400.755 (PHQ 89.018A). 
     (3a) EP-A 457,390 (PHN 13.328). 
     (3b) EP-A 457,391 (PHN 13.329). 
     (4) EP-A 65,148.