Patent Publication Number: US-6219641-B1

Title: System and method of transmitting speech at low line rates

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of telecommunications and speech recognition, and more particularly to an apparatus and method of ultra high speech compression and language translation. 
     BACKGROUND OF THE INVENTION 
     As is well known, computer systems, or more generally, any central processor unit (CPU) machine, typically receive input and produce output via traditional devices such as keyboard input, tape, disk, and CD-rom. By way of example, a first user may type a letter into a computer system via a computer keyboard. The keyboard input is typically displayed on a monitor. From there, the letter may be electronically stored on a disk drive, printed on a printer, or electronically mailed (i.e., E-mail) over a communications network like a local area network (LAN) to a second user using some other computer system on the LAN. The second user receives notification of the received letter (i.e., E-mail notification) and uses his computer system and its corresponding E-mail system to display the received letter. 
     As is also known, methods have been developed to provide voice recognition for computer input in place of keyboard input. With such voice recognition methods, a user speaks into a sound subsystem of the computer and through a matching of the user&#39;s vocabulary with a voice recognition dictionary stored in the computer system, the user&#39;s spoken words are converted to digital signals and processed and/or stored in the computer system. Further, it is known that computer systems having sound subsystems coupled to a text-to-speech engine may match digitally stored words with spoken words and produce the audible words through the sound subsystems. 
     It is also well known that present speech compression algorithms like different variants of LPC (Linear Prediction Coding), such as MELP and CELP, may provide compression rates of 2.4 kilobits per second (Kbps) or lower. What is desired is a method and system that approaches compression rates under 100 bits per second and thus provides ultra high speech compression (and language translation) between two parties. 
     SUMMARY OF THE INVENTION 
     In accordance with the principles of the present invention a method of transmitting spoken words is provided including a speech recognition engine in a computer system, the speech recognition engine having a data dictionary containing a number of words associated with a corresponding number of codes, receiving a word in a microphone system of the computer system, recognizing the word, checking the word in the data dictionary for an associated code, assigning the word the associated code, determining whether another word has been received, repeating the steps of recognizing, checking, assigning, as long as one determines there are new input words, packing the associated codes into a first sequence; and transmitting the first sequence via a communication link attached to the computer system. Furthermore, as an enhancement, translating the phrases before encoding them provides automatic language translation. 
     At the receiving side, decomposing the received sequence of codes, transforming the sequence of codes into text words and reproducing the text into the original or the translated speech through a text to speech engine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as features and advantages thereof, will be best understood by reference to the detailed description of specific embodiments which follows, when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a block diagram of an exemplary ultra high speech compression system in a transmitting computer system in accordance with the present invention; 
     FIG. 2 is a block diagram of an exemplary ultra high speech compression and language translation system in a transmitting computer system in accordance with the present invention; 
     FIG. 3 is a block diagram of an exemplary ultra high speech compression system in a receiving computer system in accordance with the present invention; 
     FIG. 4 is an illustrative example of word coding in accordance with the present invention; 
     FIG. 5 is a flow chart illustrating the steps of an ultra high speech compression and language translation method in transmitting voice data in accordance with the present invention; and 
     FIG. 6 is a flow chart illustrating the steps of an ultra high speech compression and language translation method in receiving voice data in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring to FIG. 1 an exemplary ultra high speech compression system  10  is shown to include a microphone  12  connected to an exemplary transmitting computer system  14 . The transmitting computer system  14  is shown to include a speech recognition engine  16 . The speech recognition engine  16  of the transmitting computer system  14  is shown connected to a coder  20  that uses a dictionary database  18 . In an exemplary operation, speech is received by the microphone  12  and recognized in the speech recognition engine  16 . Once recognized, the spoken words are encoded using the dictionary database  18 , and with this the speech is virtually compressed and sent out over a transport network  24 . 
     Referring to FIG. 2 the exemplary ultra high speech compression system  10  of FIG. 1 includes an enhancement of speech (or language) translation. By way of example, language A words are spoken into the microphone  12  and recognized by the speech recognition engine  16 . The recognized phrases are passed through the language translation engine  30 , which outputs phrases in language B, for example. The words in language B are encoded by the coder  20  using a language B dictionary  32  and a sequence of codes (not shown) representing compressed and translated speech is sent over the transport network  24 . 
     Referring to FIG. 3, an exemplary ultra high speech compression system in a receiving computer system  41  is illustrated. A sequence of codes (not shown) is received in the transport network  24  and passed through a decoder  46  which parses the codes and transforms it into a sequence of words using the dictionary  50 . One should note that this dictionary is the same one used at the transmitting side to assign codes to the recognized words of FIG. 1 and 2, but the operation is reversed. Further, the decoded words are passed through the text to speech engine  48  and reproduced as spoken words in a sound system  52 . 
     Referring to FIG. 4, an example of how the speech recognition engine  16  and the coder  20  codes speech is illustrated. As seen in FIG. 3, each word of the sentence “This is an example of compression” is assigned a unique code. Specifically, the word “This” is assigned the number “7,” the word “is” is assigned the number “4,” the word “an” is assigned the number “2,” the word “example” is assigned the number “132,” the word “of” is assigned the number “285,” and the word “compression” is assigned the number “473.” Thus, in this example, the sentence “This is an example of compression” results in a string of assigned numbers, i.e., “7 4 2 132 285 473.” 
     What the example of FIG. 4 illustrates is the recognition of words and the mapping of each word, through a one to one mapping process, to a unique code sequence. The mapping is performed according to the dictionary database  18  in FIG. 1 or  32  in FIG.  2 . For N words the dictionary database would require code words of [log(base 2)N] bits length. For example, a one thousand (1000) word dictionary have 10 bits long code words. 
     Ultra high compression results through sending the sequence of codes instead of compressed speech information over transport network  24 . At the reception of codes, the sequence of codes is transformed, i.e., unpacked and decoded, through the same mapping applied to the same dictionary data base (same means the dictionary and mapping used at the source side). The resultant text is then passed through the text to speech engine  48  (of FIG. 3) and thus the original speech information is reproduced at a receiving side. Thus at the receiving side the code sequence “7 4 2 132 285 473” is transformed into the original phrase “This is an example of compression”. 
     It is preferred that the text to speech engine  48  (of FIG. 2) on the reception uses speech parameters like the pitch and the gain exactly as they were detected on the source side, in order to reproduce the transported speech. 
     In one more example, a two second phrase like “we like to highly compress speech”, passed on the source side through the speech recognition engine  16  of FIG. 1 or FIG. 2, results in a sequence of six recognized words. The sequence of the six recognized words is mapped using the dictionary data base  18  or  32  in a sequence of six codes. If the dictionary database contains one thousand words dictionary, this phrase may be encoded in six 10 bit codes or 60 bits. This would result in a rate of 60 bits per 2 seconds, or 30 bits per second. 
     It should be noted that adding a language translation engine ( 30  in FIG. 2) to the speech recognition engine  16  would provide an additional service of language translation, i.e., if a speaker speaks language A, a receiver may receive language B. 
     Referring to FIG. 5, a flow chart illustrating the steps of an ultra high speech compression method in making a transmission of voice data in accordance with the present invention starts at step  100  when a word of speech is received. At step  101  the word is recognized. At step  102  the received word is checked against the data dictionary. If at step  104  the received word is found not to be in the data dictionary, at step  106  a new word-to-code association is created and at step  108  stored in the data dictionary. If at step  104  the received word is in the data dictionary, at step  110  the received word is mapped to its corresponding code. If at step  112  another word is received, the process loops back to step  102 . If at step  112  there are no more received words to check and map, at step  114  the string of codes, representing the string of received words, is packed for transmission. At step  116  the packed string of codes is transmitted and the process ends at step  118 . 
     Referring to FIG. 6, a flow chart illustrating the steps of an ultra high speech compression method in making a reception of voice data in accordance with the present invention starts at step  200  when a packed string of codes is received. At step  202  the received packed string of codes is unpacked. At step  204  the unpacked string of codes is parsed and at step  206  each code is mapped to its corresponding word. At step  208  each word is outputted, i.e., reproduced as a sound word, in a text to speech engine, and the process ends at step  210 . 
     Having described a preferred embodiment of the invention, it will now become apparent to those skilled in the art that other embodiments incorporating its concepts may be provided. It is felt therefore, that this invention should not be limited to the disclosed invention, but should be limited only by the spirit and scope of the appended claims.