Speech reproducing device capable of reproducing long-time speech with reduced memory

A speech reproducing device includes a data processing unit for processing a received radio frequency signal to generate speech data, a memory for storing the speech data on a basis of several speech frames, each having a predetermined length, a speech decoding unit for decoding speech data stored in the memory to generate a speech signal, a speech reproducing unit for reproducing and outputting speech based on a generated decoded speech signal and a telephone control unit for controlling operation of each unit to read speech frames in the memory while appropriately thinning out them as necessary to reproduce speech.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a speech reproducing device for 
controlling processing for reproducing received speech data and, more 
particularly, to a speech reproducing device in which the amount of memory 
needed is reduced so as to reproduce long-time speech such as 
conversation. 
2. Description of the Related Art 
One conventional speech reproducing device for controlling operation in a 
speech reproducing system which reproduces received speech data is 
disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) 
No. Heisei 1-116699. The structure of the speech reproducing device 
described in this literature is shown in FIG. 4. 
In this conventional speech reproducing device, a discrimination circuit 
101 detects an input from a microphone 100 and supplies a write 
instruction signal to a memory 102 to store the input from the microphone 
100 in the memory 102 in response to a predetermined clock signal. Then, a 
reproduction speed selecting switch 103 selects a reproduction speed of 
speech data stored in the memory 102 and the speech data is read at the 
selected speed based on a clock whose speed is determined by a read 
instruction signal output by a reproduction control circuit 104. In other 
words, speech data written on the memory 102 is reproduced at an arbitrary 
speed through control of the clock speed at which it is read out of speed 
determined by the reproduction speed selecting switch. 
The above-descried conventional speech reproducing device, however, has a 
drawback that the capacity of the memory 102 is not sufficient for 
recording speech data of common conversations. 
More specifically, the above-described conventional speech reproducing 
device is intended for storing speech data of a single, relatively short 
period of conversation and is therefore practical in terms of that 
objective. However, it is not unusual for common conversation to take 
several tens of minutes. Speech data of such conversation is so enormous 
that the memory 102 used in the above speech reproducing device does not 
have sufficient capacity to store the entire part of such conversation. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a speech reproducing 
device in which a shortage of memory capacity caused by an overflow in 
speech data is eliminated, making it possible to use the device in 
connection with common long-time conversations. 
According to one aspect of the invention, a device for reproducing speech 
from a received radio frequency signal, comprising: 
(A) data processing means for processing a received radio frequency signal 
representative of a conversation, said data processing means processing 
said received radio frequency signal to generate speech data comprising a 
plurality of consecutive speech frames, each of said speech frames being 
representative of a respective time segment of said received radio 
frequency signal, each of said time segments being of equal length; 
(B) storing means for storing each consecutive said speech frame generated 
by said data processing means; and 
(C) selecting means for selecting a magnification ratio indicative of the 
speed at which said conversation is to be reproduced; 
(D) sound reproduction means for reproducing said conversation, said sound 
reproduction means comprising: 
(1) deleting means for deleting a number of speech frames, and therefor a 
segment of said conversation, stored in said storing means at a rate which 
is determined by said magnification ratio, whether or not a given set of 
speed frame are deleted being and which is independent of whether or not a 
segment of said conversation corresponding to said set of speech frames 
corresponds to a silent portion of said conversation; and 
(2) reproducing means for reproducing said conversation by converting those 
of said speech frames which are not deleted into an audible signal. 
According to another aspect of the invention, a process for reproducing 
speech from a received radio frequency signal comprises: 
(A) processing a received radio frequency signal representative of a 
conversation so as to generate speech data comprising a plurality of 
consecutive speech frames, each of said speech frame being representative 
of a respective time segment of said received radio frequency signal, each 
of said time segments being of equal length; 
(B) storing each consecutive said speech frame generated by said data 
processing means; and 
(C) reproducing said conversation by: 
(1) deleting a number a of said stored speech frames, and therefore a 
segment of said conversation, at a rate which is determined by a 
magnification ratio indicative of the speech at which said conversation is 
to be reproduced, said speed being independent of whether or not said 
segment of said conversation corresponds to a silent portion of said 
conversation; 
(2) reproducing said conversation by converting those of said speech frames 
which are not deleted into an audible signal. 
In the preferred construction, the control means comprises setting means 
for setting a thinning-out rate of said speech frames by specifying a 
speech reproduction speed in said speech reproducing means. 
In the preferred construction, the control means comprises setting means 
for setting a thinning-out rate of said speech frames by specifying a 
speech reproduction speed in said speech reproducing means, read control 
means for reading the speech frames in said storing means while thinning 
out them, and sending the read speech frames to said speech decoding means 
in accordance with the setting by said setting means, and reproduction 
control means for controlling said speech reproducing means to reproduce 
speech while complementing a part of the speech frames thinned out by said 
read control means in accordance with the setting by said setting means, 
the read control means reads a speech frame positioned at the top of the 
speech frames in said storing means, deletes speech frames following said 
read speech frame in accordance with a thinning-out rate set by said 
setting means, and shifts speech data subsequent to said deleted speech 
frames to the top of said storing means. 
In another preferred construction, the control means comprises setting 
means for setting a thinning-out rate of said speech frames by specifying 
a speech reproduction speed in said speech reproducing means by a ratio to 
a normal reproduction speed, read control means for reading the speech 
frames stored in said storing means while thinning out them, and sending 
the read speech frames to said speech decoding means in accordance with 
the setting by said setting means, and reproduction control means for 
controlling said speech reproducing means to reproduce speech while 
complementing a part of the speech frames thinned out by said read control 
means in accordance with the setting by said setting means, 
the read control means reads a speech frame positioned at the top of the 
speech data stored in said storing means, deletes as many speech frames as 
the number obtained by subtracting the numerical value of 1 from a value 
of said ratio to a normal reproduction speed set by said setting means out 
of the speech frames following said read speech frame, and shifts a speech 
frame subsequent to said deleted speech frames to the top of said storing 
means. 
In the above-mentioned construction, the control means comprises setting 
means for setting a thinning-out rate of said speech frames by specifying 
a speech reproduction speed in said speech reproducing means, read control 
means for reading the speech frames stored in said storing means while 
thinning out them, and sending the read speech frames to said speech 
decoding means in accordance with the setting by said setting means, and 
reproduction control means for controlling said speech reproducing means 
to reproduce speech while complementing a part of the speech frames 
thinned out by said read control means in accordance with the setting by 
said setting means, 
the read control means reads a speech frame positioned at the top of the 
speech frames stored in said storing means, deletes as many speech frames 
as the number according to the thinning-out rate set by said setting means 
out of the speech frames following said read speech frame, and shifts a 
speech frame subsequent to said deleted speech frames to the top of said 
storing means, and 
the reproduction control means extends a speech reproduction time by 
changing the speech reproduction speed of said speech reproducing means in 
accordance with the speech reproduction speed specified by said setting 
means to complement a part of the speech frames thinned out by said read 
control means. 
Also, the control means comprises setting means for setting a thinning-out 
rate of said speech frames by specifying a speech reproduction speed in 
said speech reproducing means, read control means for reading the speech 
frames stored in said storing means while thinning out them, and sending 
the read speech frames to said speech decoding means in accordance with 
the setting by said setting means, and reproduction control means for 
controlling said speech reproducing means to reproduce speech while 
complementing a part of the speech frames thinned out by said read control 
means in accordance with the setting by said setting means, 
the read control means reads a speech frame positioned at the top of the 
speech frames stored in said storing means, deletes as many speech frames 
following said read speech frame as the number according to the 
thinning-out rate set by said setting means, and shifts a speech frame 
subsequent to said deleted speech frames to the top of said storing means, 
and 
the reproduction control means copies and arranges one speech frame of the 
speech signal decoded by said speech decoding means in accordance with the 
speech reproduction speed specified by said setting means to complement 
the part of the speech frames thinned out by said read control means. 
In another preferred construction, the control means comprises setting 
means for setting a thinning-out rate of said speech frames by specifying 
a speech reproduction speed in said speech reproducing means by a ratio to 
a normal reproduction speed, read control means for reading the speech 
frames stored in said storing means while thinning out them, and sending 
the read speech frames to said speech decoding means in accordance with 
the setting by said setting means, and reproduction control means for 
controlling said speech reproducing means to reproduce speech while 
complementing a part of the speech frames thinned out by said read control 
means in accordance with the setting by said setting means, and 
the read control means reads a speech frame positioned at the top of the 
speech data stored in said storing means, deletes as many speech frames as 
the number obtained by subtracting the numerical value of 1 from a value 
of said ratio to a normal reproduction speed set by said setting means out 
of the speech frames following said read speech frame, and shifts a speech 
frame subsequent to said deleted speech frames to the top of said storing 
means, and 
the reproduction control means copies one speech frame of the speech signal 
decoded by said speech decoding means as many as the number obtained by 
subtracting the numerical value of 1 from a value of said ratio to a 
normal reproduction speed specified by said setting means and arranges the 
copied signals into said decoded speech signal to complement a part of the 
speech frames thinned out by said read control means. 
Other objects, features and advantages of the present invention will become 
clear from the detailed description given herebelow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred embodiments of the present invention will be descried in detail 
with reference to the accompanying drawings. 
FIG. 1 is a block diagram showing the structure of a speech reproducing 
device according to a first embodiment of the present invention. The 
present embodiment will be described with respect to a case where a speech 
reproducing device is applied to a portable telephone. 
As shown in FIG. 1, the speech reproducing device of the present embodiment 
includes a radio frequency (RF) processing unit 12, a data processing unit 
13, a memory 14 and a speech decoding unit 15 for processing a radio 
frequency (RF) signal S1 received by an antenna 11 to generate a speech 
signal, a speech reproducing unit 16 and a speaker 17 for outputting 
speech based on a reproduced speech signal, a telephone control unit 30 
connected to each unit for controlling the same through a bus 20, and a 
key entry display unit 41, a selecting switch 42 and a reproduction speed 
setting key 43 for setting the telephone control unit 30 in a 
predetermined manner. In the figure, illustration is made only of 
characteristic components of the present embodiment and that of the other 
components is omitted. 
The RF processing unit 12, which is implemented by a program-controlled CPU 
or the like, demodulates a received RF signal S1 to generate an 
information signal S2 under control of the telephone control unit 30. The 
information signal S2 is applied to the data processing unit 13. 
The data processing unit 13, which is implemented by a program-controlled 
CPU or the like, executes such processing as equalization and error 
correction in response to the information signal S2 sent from the RF 
processing unit 12 to generate speech data S3 under control of the 
telephone control unit 30. Generated speech data S3 is output to the 
memory 14. 
The memory 14, which is implemented by a main storage device such as an 
RAM, reads and stores several frames of the speech data S3 sent from the 
data processing unit 13 under control the telephone control unit 30. 
The speech decoding unit 15, which is implemented by a program-controlled 
CPU or the like, reads coded speech data S3 stored in the memory 14 and 
decodes the read data at a preset speed to generate a speech signal S4 
under control of the telephone control unit 30. Generated speech signal S4 
is output to the speech reproducing unit 16. 
The speech reproducing unit 16, which is implemented by a 
program-controlled CPU or the like, reproduces the speech signal S4 sent 
from the speech decoding unit 15 at a preset speed to output speech 
through the speaker 17. The speaker 17, which is a component provided 
simply for outputting speech, can be replaced by other components for 
outputting speech such as an earphone. 
The selecting switch 42 is used to change the speed with which the speech 
decoding unit 15 decodes the speech data S3 and a speed with which the 
speech reproducing unit 16 reproduces the speech signal S4. When the 
selecting switch 42 is turned on, a speed change signal S5 is applied to 
the telephone control unit 30. The signal S5 indicates a desired change of 
a decoding speed of the speech data S3 or a reproduction speed of the 
speech signal S4. 
The reproduction speed setting key 43 is used to set a desired reproduction 
speed which will be used by speech decoding unit 15 and speech reproducing 
unit 16 when the selecting switch 42 is placed on the ON state. Setting of 
the value of the speech reproduction speed can be executed in an arbitrary 
manner. For example, the value is set by specifying a fraction or a 
percentage of a normal reproduction speed. 
The key entry display unit 41, which is implemented by a display device or 
the like, is for enabling an operator to observe whether the selecting 
switch 42 is ON or OFF and to observe the contents entered by the 
reproduction speed setting key 43 for reliable setting operation. 
The telephone control unit 30 includes a selecting switch determining unit 
31 for accepting an input from the selecting switch 42, a magnification 
ratio control unit 32 for accepting entry of the reproduction speed 
setting key and a read control unit 33 for controlling the reading 
operation of the speech frame S3 from the memory 14 by the speech decoding 
unit 15. 
The selecting switch determining unit 31, which is implemented by a 
program-controlled CPU or the like, accepts an input from the selecting 
switch 42 to determine whether the selecting switch 42 is in the ON state. 
When it is determined that the selecting switch 42 is in the ON state, the 
unit 31 enables the magnification ratio control unit 32. 
The magnification ratio control unit 32, which is implemented by a 
program-controlled CPU or the like, determines a speech reproduction speed 
for the speech reproducing unit 16 based on a speed magnification ratio 
set by the reproduction speed setting key 43. For example, when setting of 
a speech reproduction speed is carried out by specifying a fraction of a 
normal speed and if the set value of the entered reproduction speed 
setting key 43 is the magnification ratio of n, the speed with which the 
speech signal S4 is reproduced by the speech reproducing unit 16 is slowed 
down to one-nth the normal speed. That is, the speech signal S4 is 
reproduced in a time period n times longer than a normal time period. In 
other words, an output time of the speech obtained by the reproduction of 
the speech signal S4 is extended n times that which is required when the 
speech signal is reproduced at a normal reproduction speed. The 
magnification ratio control unit 32 outputs a control signal S6, 
indicative of existence/non-existence and contents of setting of a 
reproduction speed by the reproduction speed setting key 43, to the read 
control unit 33. 
During normal operation (when receiving no input of the control signal S6 
from the magnification ratio control unit 32), read control unit 33, which 
is implemented by a program-controlled CPU or the like, sequentially reads 
the leading data on a frame basis (i.e., the oldest frame in the memory) 
from the memory 14 and shifts the subsequent data to the top of the memory 
14. During a speed changing operation (i.e., when receiving an input of 
the control signal S6 output from the magnification ratio control unit 
32), the read control unit 33 also reads one frame of the leading data of 
the speech data S3 from the memory 14 (i.e., the oldest stored frame) and 
outputs the read data to the speech decoding unit 15. In this case, 
however the read control unit 33 deletes n-1 (n being the magnification 
ratio) speech frames following the speech frame read out of memory 14 and 
shifts the remaining speech frames to the top of the memory 14. When a 
speed magnification ratio set by the reproduction speed setting key 43 is 
n-5, for example, n-4 frames starting at the second frame subsequent to 
the first frame read out of memory and ending at the fourth frame are 
deleted. As used herein, the phrase "one frame of data" denotes a single 
speech frame, which is a unit of information of speech data reproduced by 
the data processing unit 13. The speech data S3 is read every n frames and 
decoded by the speech decoding unit 15 through the foregoing operation. 
Operation of the present embodiment will be described with reference to the 
flow chart of FIG. 2. 
In FIG. 1, the received RF signal S1 is demodulated by the RF processing 
unit 12, output as the information signal S2 to the data processing unit 
13, and then output as the speech data S3 through processing such as 
equalization and error correction. Determination is made by the selecting 
switch determining unit 31 whether the selecting switch 42 is in the ON 
state or not (Step 201). When the determination is made that the selecting 
switch 42 is in the ON state, the magnification ratio control unit 32 
starts control operation (YES at Step 201). Then, the speed magnification 
ratio n set by the reproduction speed setting key 43 is determined, and 
the speech decoding unit 15 and the speech reproducing unit 16 are 
controlled to output the control signal S6 (Step 202). 
In the following, each operation will be described with respect to a case 
where the set value of the reproduction speed setting key 43 is the 
magnification ratio of 3. 
First, the magnification ratio control unit 32 outputs the control signal 
S6 indicating that a speech reproduction speed is set to the magnification 
ratio of 3 by the reproduction speed setting key 43. In response to the 
control signal S6, the read control unit 33 reads one frame of the leading 
data from the memory 14 and sends it to the speech decoding unit 15, 
whereby the one frame of speech data S3 is decoded and converted into the 
speech signal S4 and then sent to the speech reproducing unit 16 by the 
speech decoding unit 15. Then, the speech signal S4 is reproduced by the 
speech reproducing unit 16 at one-third the normal reproduction speed and 
output to the speaker 17 (Step 203). 
In addition, two frames (equal to the set magnification ratio 3 minus 1), 
that is, second and third frames following the read first frame, are 
deleted from the memory 14 and the subsequent fourth frame is shifted to 
the top of the memory 14 by the read control unit 33 (Step 204). 
The respective processing will be repeated hereafter, determination of the 
state of the selecting switch 42, setting of a reproduction speed, reading 
and reproduction of one frame of the speech data S3 from the memory 14 and 
shifting operation of subsequent data (steps 201 to 204). 
In this state, when the selecting switch 42 is turned off, the selecting 
switch determining unit 31 determines that the selecting switch 42 is in 
the OFF state to stop operation of the magnification ratio control unit 
32. As a result, the magnification ratio control unit 32 fails to output 
the control signal S6 to the read control unit 33. 
At this point, the read control unit 33 starts normal operation, so that 
the leading data is sequentially read from the memory 14 on a frame basis, 
the read speech data S3 is decoded by the speech decoding unit 15 and the 
decoded speech signal S4 is reproduced at a normal reproduction speed by 
the speech reproducing unit 16 and output through the speaker 17 (Step 
205). In addition, the read control unit 33 sequentially shifts each frame 
subsequent to the read first frame to the top of the memory 14 (Step 206). 
The second embodiment of the present invention will be described in the 
following. 
The speech reproducing device of the present embodiment is similarly 
structured to the speech reproducing device of the first embodiment shown 
in FIG. 1. The present embodiment only differs in the function of the 
magnification ratio control unit 32 of the telephone control unit 30 from 
that of the above-described magnification ratio control unit 32 of the 
first embodiment. The other components are the same as those in the 
above-described first embodiment. 
Based on a speed magnification ratio set by the reproduction speed setting 
key 43, the magnification ratio control unit 32 of the present embodiment 
copies and arranges the speech signal decoded by the speech decoding unit 
15 as many as the value of the speed magnification ratio and controls the 
speech reproducing unit 16 to reproduce the same. At this time, unlike the 
control by the magnification ratio control unit 32 in the first 
embodiment, reproduction is carried out at a normal reproduction speed, 
without changes in the speech reproduction speed of the speech reproducing 
unit 16. 
More specific description will be made, with reference to the flow chart of 
FIG. 3, of a case where a speech reproduction speed is to be set by 
specifying a fraction of a normal speed and a set value of the entered 
reproduction speed setting key 43 is a magnification ratio of n. The 
magnification ratio control unit 32 first outputs the control signal S6 to 
wait for the speed data S3 to be read by the read control unit and to be 
decoded by the speech decoding unit 15 (Steps 301 and 302). When decoding 
of the speech signal is executed by the speech decoding unit 15, the 
magnification ratio control unit 32 copies and arranges the decoded speech 
signal S4 as many as n-1 (Step 303). As a result, the same speech signals 
S4 as many as the number of n are arranged. Then, the unit 32 controls the 
speech reproducing unit 16 to reproduce the arranged n speech signals S4 
(Step 304). As a result, speech obtained by the reproduction of the speech 
signal S4 is repeatedly output n times. 
In other words, while in the first embodiment a reproduction time of the 
speech signal S4 is extended to a time corresponding to a set speed 
magnification ratio, in the present embodiment reproduction of the speech 
signal S4 is appropriately repeated to output speech based on the speech 
signal for a desired time period. 
As described in the foregoing, in the speech reproducing device of the 
present invention not all the speech data but several speech frames are 
written in a memory and thinned out for decoding. Then, a generated speech 
signal is expanded or the speech signal is repeatedly reproduced to 
complement speech corresponding to thinned out speech frames. This enables 
the necessary amount of memory to be reduced to eliminate a shortage of 
memory capacity caused by overflow speech data, thereby coping with common 
long-time conversation. 
Although the invention has been illustrated and described with respect to 
exemplary embodiment thereof, it should be understood by those skilled in 
the art that the foregoing and various other changes, omissions and 
additions may be made therein and thereto, without departing from the 
spirit and scope of the present invention. Therefore, the present 
invention should not be understood as limited to the specific embodiment 
set out above but to include all possible embodiments which can be 
embodies within a scope encompassed and equivalents thereof with respect 
to the feature set out in the appended claims.