Back to results
US 6,687,368 B1Granted
Tone signal detecting method and tone signal detector
AssigneeOki Electric Industry Co., Ltd.
InventorsHiromi Aoyagi, Atsushi Shimbo
Life of this patent
Estimating the term…
Abstract
A method for detecting a tone signal includes determining a correlative value of an input signal obtained for each frame of a predetermined length, determining an estimating expression that represents an output power of a second order FIR band elimination filter that uses the correlative value of the input signal as an input and a frequency thereof as a parameter, determining a frequency at which a minimum value of the estimating expression is obtained, determining a prediction gain of the FIR band elimination filter at the determined frequency, and determining that the input signal is a tone signal if a value of the determined prediction gain exceeds a preset threshold value.
Claims10
A method for detecting a tone signal, comprising the steps of:
- determining a correlative value of an input signal obtained for each frame of a predetermined length;
- determining an estimating expression that represents an output power of a second order FIR band elimination filter that uses said correlative value of the input signal as an input and a frequency thereof as a parameter;
- determining a frequency at which a minimum value of said estimating expression is obtained;
- determining a prediction gain of said FIR band elimination filter at said determined frequency;
- and
- determining that the input signal is a tone signal if a value of said determined prediction gain exceeds a preset threshold value.
3 more elements
A tone signal detector comprising:
- a correlative value calculating circuit for determining a correlative value of an input signal obtained for every frame of a predetermined length;
- and
- a tone determining unit that has an output power calculating section that determines an estimating expression representing an output power of a second order FIR band elimination filter that uses said correlative value of the input signal as an input and a frequency thereof as a parameter, a minimum frequency calculating section that determines a frequency at which a minimum value of said estimating expression can be obtained, a prediction gain calculating section that determines a prediction gain of said FIR band elimination filter at the frequency determined by said minimum frequency calculating section, and a prediction gain comparing section that compares a value of said prediction gain determined by said prediction gain calculating section with a preset threshold value, and said tone determining unit determines that the input signal is a tone signal if said prediction gain exceeds said threshold value.
A method for detecting a tone signal comprising the steps of:
- determining a correlative value of an input signal obtained for each frame of a predetermined length;
- determining an estimating expression that represents an output power of a second order FIR band elimination filter that uses said correlative value of the input signal as an input and a frequency thereof as a parameter;
- determining a cosine value of a frequency at which a minimum value of said estimating expression is obtained;
- comparing said cosine value with a preset threshold value to decide that the frequency is a frequency candidate if said cosine value is within a range of said threshold value;
- determining an input signal power;
- multiplying an estimated value into which said determined cosine value has been substituted by a preset constant;
- comparing said estimated value multiplied by said constant with said input signal power;
- determining that the input signal is a tone signal candidate if said estimated value multiplied by said constant is below said input signal power and if the frequency thereof has been determined to be said frequency candidate;
- and
- detecting the input signal as a tone signal if said tone signal candidate determination is repeated for a preset number of times or more.
7 more elements
A tone signal detector comprising:
- a correlative value calculating circuit for determining a correlative value of an input signal obtained for every frame of a predetermined length;
- and
- a tone determining unit that has an output power calculating section that determines an estimating expression representing an output power of a second order FIR band elimination filter that uses said correlative value of the input signal as an input and a frequency thereof as a parameter, a minimum cosine value calculating section that determines a cosine value of a frequency at which a minimum value of said estimating expression can be obtained, a frequency candidate determining section that compares said cosine value with a preset threshold value and determines that the frequency is a frequency candidate if said cosine value lies within a range of said threshold value, and a power comparing section that compares an estimated value into which said determined cosine value has been substituted with an input signal power, and determines that the input signal is a tone signal candidate if a comparison result of said power comparing section indicates that said estimated value is below said input signal power and if said frequency candidate determining section determines that the frequency is a frequency candidate;
- a tone time determining unit detects the input signal as a tone signal if the determination of a tone signal candidate by said tone determining unit is repeated for a preset number of times or more.
1 more element
A method for detecting a tone signal comprising the steps of:
- obtaining a low-band signal by removing a high group frequency from an input signal obtained for each frame of a predetermined length;
- determining a low-band signal correlative value of said low-band signal;
- determining a low-band estimating expression representing an output power of a second order FIR band elimination filter when said low-band signal is used as an input and a frequency thereof is used as a parameter;
- determining a low-band cosine value of a low-band frequency at which a minimum value of said low-band estimating expression is obtained;
- comparing said low-band cosine value with a preset low-band threshold value;
- deciding that the frequency is a low-band frequency candidate if said low-band cosine value lies within a range of said low-band threshold value;
- determining a low-band signal power of said low-band signal;
- multiplying a low-band estimated value into which said determined low-band cosine value has been substituted by a preset low-band constant;
- comparing said low-band estimated value multiplied by said low-band constant with said low-band signal power;
- deciding that the input signal is a low-band tone signal candidate if said low-band estimated value multiplied by said low-band constant is below said low-band signal power and if the input signal has been determined to be said low-band frequency candidate;
- obtaining a high-band signal by removing a low group frequency from an input signal obtained for each frame of said predetermined length;
- determining a high-band signal correlative value of said high-band signal;
- determining a high-band estimating expression representing an output power of a second order FIR band elimination filter when said high-band signal is used as an input and a frequency thereof is used as a parameter;
- determining a high-band cosine value of a high-band frequency at which a minimum value of said high-band estimating expression is obtained;
- comparing said high-band cosine value with a preset high-band threshold value;
- deciding that the frequency is a high-band frequency candidate if said high-band cosine value lies within a range of said high-band threshold value;
- determining a high-band signal power of said high-band signal;
- multiplying a high-band estimated value into which said determined high-band cosine value has been substituted by a preset high-band constant;
- comparing said high-band estimated value multiplied by said high-band constant with said high-band signal power;
- deciding that the input signal is a high-band tone signal candidate if said high-band estimated value multiplied by said high-band constant is below said high-band signal power and if the input signal has been determined to be said high-band frequency candidate;
- and
- detecting the input signal as a DTMF signal if a state, wherein the input signal has been determined to be said low-band tone signal candidate and said high-band tone signal candidate, is repeated for a preset number of times or more in succession.
19 more elements
A tone signal detector comprising:
- a filter for obtaining a low-band signal by removing a high group frequency from an input signal obtained for every frame of a predetermined length;
- a low group correlative value calculating circuit for determining a low-band signal correlative value of said low-band signal;
- a low group tone determining unit that has a low-band output power calculating section that determines a low-band estimating expression representing an output power of a second order FIR band elimination filter that uses said low-band signal as an input and a frequency thereof as a parameter, a low-band minimum cosine value calculating section that determines a low-band cosine value of a low-band frequency at which a minimum value of said low-band estimating expression can be obtained, a low-band frequency candidate determining section that compares said low-band cosine value with a preset low-band threshold value and determines that the frequency is a low-band frequency candidate if said low-band cosine value lies within a range of said low-band threshold value, and a low-band power comparing section that compares a low-band estimated value into which said determined low-band cosine value has been substituted with a low-band signal power, and determines that the input signal is a low-band tone signal candidate if a comparison result of said low-band power comparing section indicates that said low-band estimated value is below said low-band signal power and if said low-band frequency candidate determining section determines that the frequency is a low-band frequency candidate;
- a filter for obtaining a high-band signal by removing a low group frequency from an input signal obtained for every frame of said predetermined length;
- a high group correlative value calculating circuit for determining a high-band signal correlative value of said high-band signal;
- a high group tone determining unit that has a high-band output power calculating section that determines a high-band estimating expression representing an output power of a second order FIR band elimination filter that uses said high-band signal as an input and a frequency thereof as a parameter, a high-band minimum cosine value calculating section that determines a high-band cosine value of a high-band frequency at which a minimum value of said high-band estimating expression can be obtained, a high-band frequency candidate determining section that compares said high-band cosine value with a preset high-band threshold value and determines that the frequency is a high-band frequency candidate if said high-band cosine value lies within a range of said high-band threshold value, and a high-band power comparing section that compares a high-band estimated value into which said determined high-band cosine value has been substituted with a high-band signal power, and determines that the input signal is a high-band tone signal candidate if a comparison result of said high-band power comparing section indicates that said high-band estimated value is below said high-band signal power and if said high-band frequency candidate determining section determines that the frequency is a high-band frequency candidate;
- and
- a time determining unit that detects the input signal as a DTMF signal if a state, wherein the input signal is determined to be a low-band tone signal candidate by said low group tone determining unit and determined to be a high-band tone signal candidate by said high group tone determining unit, is repeated for a preset number of times or more in succession.
5 more elements
Dependencies are inferred from the claim text.