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Implementation
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interface to the rest of the system and a “wiretap” program which translates binary
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program output into human-readable form.
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The speech processing modules all share a common interface configuration.
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Each module has an input port and an output port (these are the UNIX standard
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input and standard output channels, respectively). Module input can come from
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either a disk file or from the output port of the preceding module (via a UNIX
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pipe). Module output can be directed to a disk file or to the input port of the next
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module. A group of modules connected together in sequence is called a pipeline in
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UNIX terminology.
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The top level program, called MITALK, handles the creation of a speech
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processing pipeline. The user can call for the entire pipeline or any subsequence of
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the pipeline. The user specifies the names of the first and last modules in the
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desired pipeline and MITALK creates the pipeline processes. If the first module is
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FORMAT, then the user can provide input text directly from the terminal. If any
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other module is first, then its input must come from a previously created disk file.
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If the last module is COEWAY, then output can be sent to a digital-to-analog con-
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verter to be played aloud. The output from other modules can be sent to a disk file
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or can be translated from raw binary to human-readable form for display on the
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user’s terminal. The program SHOW is used to perform the translation.
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14.5 Using the system
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Figure 14-1 demonstrates most of the features of the system. This figure contains
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a complete copy of a MITalk session. User-typed text is in boldface. The first line
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of text is the user’s command to the UNIX shell to start the top-level process with
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the given list of parameters. Next, MITALK decodes the parameters to determine
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the appropriate pipeline structure. In this case, the pipeline begins with FORMAT
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receiving input from the user terminal (tty) and ends with SOUNDI1 sending output
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to the terminal. In addition, the contents of the pipe streams between DECOMP
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and PARSER, and between PARSER and SOUNDI, are displayed on the terminal.
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Output from each module is prefixed by the module name.
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