WO2000070602A1 - Method of evaluating the rhythmicity of a digital signal composed of samples - Google Patents
Method of evaluating the rhythmicity of a digital signal composed of samples Download PDFInfo
- Publication number
- WO2000070602A1 WO2000070602A1 PCT/FI2000/000445 FI0000445W WO0070602A1 WO 2000070602 A1 WO2000070602 A1 WO 2000070602A1 FI 0000445 W FI0000445 W FI 0000445W WO 0070602 A1 WO0070602 A1 WO 0070602A1
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- WO
- WIPO (PCT)
- Prior art keywords
- extreme value
- samples
- sample
- series
- extreme
- Prior art date
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Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/90—Pitch determination of speech signals
Definitions
- the invention relates to a method of evaluating the rhythmicity of a digital signal composed of samples.
- Rhythmicity of a digital signal composed of samples means that a certain pattern recurs regularly in the signal. For example, in a signal formed of the heart rate a stronger signal point recurs at regular intervals at the fre- quency of the heart rate. In a signal formed of speech the voicedness of speed is expressed as the rhythmicity of pitch.
- a problem related to the prior art solutions is that they require a lot of calculation capacity and are thus not suitable for simultaneous real time evaluation of the rhythmicity of several signals by a device with a relatively low capacity, such as a personal computer, or they are too inaccurate for use in practical applications. Neither do they identify momentary changes in the pitch, but provide an average value of the pitch.
- the object of the invention is to provide a method and an apparatus implementing the method to solve the above-mentioned problems. This is achieved with the method to be described in the following.
- This is a method of evaluating the rhythmicity of a digital signal composed of samples. The method comprises the following steps of: setting the next period of the signal under examination; finding local extreme values of the samples; computing the temporal distance between each two adjoining extreme value samples in turn; if at least two adjoining temporal distances differ from each other at most by a preset limit, the extreme value samples used for computing of said distances constitute a rhythmic series; repeating the steps of the method until the signal has been examined.
- the invention also relates to an apparatus for evaluating the rhythmicity of a digital signal composed of samples, comprising: a signal input; sampling means for taking samples from the signal at a certain frequency; a microprocessor for processing the samples.
- the microprocessor is arranged: to divide the signal into at least one period; find local extreme values of the samples; compute the temporal difference between each two adjoining extreme value samples in turn; to conclude: if at least two adjoining temporal differences, differ from each other at most by a preset limit, the extreme value samples used for computing said distances constitute a rhythmic series.
- the invention further relates to a memory means that can be read by a computer, comprising a computer program which is to be run in a computer and performs the method of evaluating the rhythmicity of a digital signal composed of samples.
- the method comprises the steps of: setting the next period of the signal under examination; finding local extreme values of the samples; computing the temporal difference between each two adjoining extreme value samples in turn; if at least two adjoining temporal distances differ from each other at most by a preset limit, the extreme value samples used for the computation of said distances constitute a rhythmic series; repeating the steps of the method until the signal has been examined.
- the invention is based on finding rhythmic series in a signal by means of a simple method which comprises comparing differences in temporal distances between the extreme value samples of a signal with one another.
- the method and apparatus according to the invention provide several advantages.
- the method utilizes the calculation capacity of a microprocessor efficiently. If necessary, even an ordinary personal computer can be used for finding rhythmic series in several hundreds of different signals in parallel and in real time.
- the method is also accurate and provides a detailed de- sc ption of momentary changes in rhythmicity.
- Figure 1 A is a flow chart illustrating the steps of a method according to the invention
- Figure 1 B illustrates a first preferred principal embodiment of the method according to the invention
- Figure 1C illustrates a second preferred principal embodiment of the method according to the invention
- Figures 2A and 2B illustrate how samples are taken from a signal
- Figures 3A and 3B illustrate evaluation of a signal to find rhythmicity according to the invention
- Figure 4 illustrates the essential components of an apparatus implementing the invention
- Figure 5 illustrates a method of finding extreme value samples.
- Figure 2A illustrates a signal 200 placed in a system of coordinates where the x-axis represents time T and the y-axis the signal value V at any given moment.
- the signal 200 in question is an analogue signal which can be digitised in the manner to be shown in Figure 2B.
- samples 204 are taken from the signal, which are illustrated in the figure with a line the end of which is provided with a black dot.
- the signal 200 is illustrated by the 24 samples shown.
- the signal 200 has been scaled to be placed in the system of coordinates so that the point where the x- axis crosses the y-axis is the same as the mean value of the signal.
- the mean value of the signal is represented by the x-axis 206.
- sample 204 values of the signal 200 in Figure 2B can be interpreted as being represented by different voltages.
- the y-axis represents the voltage values.
- the mean value 206 of the signal 200 is zero volts and the signal may receive values from the negative voltage values below the x-axis to the positive voltage values above the x-axis.
- the sample 204 values of the signal 200 can also be described otherwise, e.g. by scaling all values to positive or negative voltage values. Another way of illustrating the sample 204 values is in an internal presentation form of computer, e.g. as hexadecimal, octal or binary numbers. It is irrelevant to the invention how the sample 204 values are described, provided that the values are presented so that their order of magnitude and the temporal distance between the samples 204 can be determined. Referring to Figures 1A, 3A and 3B, the method of examining possible rhythmicity included in a signal according to the invention will be described in the following.
- Figure 1A illustrates the steps of the method. The method starts in block 100.
- next period 320 of the signal 200 is set under examination in block 102.
- the whole signal can also be examined in one go.
- a third possibility is to use a sliding window in which a small portion of the signal is examined, which is followed by examination of the next small portion. This method requires slightly more memory and calculation capacity than the first method since temporary information needs to be stored on how the examination proceeds during the processing.
- the examples illustrate the first method, i.e. 24 samples 204 ob- tained from the signal 200 are examined in two different periods 320 and 322.
- the local extreme values of the samples are searched for in block 104.
- the function of block 104 is performed in block 120 illustrated in Figure 1 B in which extreme value samples 301 , 302, 303, 304, 305, 306 that deviate most from the mean value 206 of the samples 204 are searched for.
- these are the samples that receive the highest and the lowest values.
- a predetermined number of samples are selected as extreme value samples 301 , 302, 303, 304, 305, 306, although other selection criteria can also be used.
- the predetermined number of extreme value samples 311 preferably depends on the type of rhythmicity. In this example six extreme value samples are selected from among each period 320, 322. For the sake of clarity, Figure 3B shows only the selected extreme value samples 301 , 302, 303, 304, 305, 306.
- the temporal distance 330, 332, 334, 336, 338 between each two adjoining extreme value samples i.e. samples 301 to 302, 302 to 303, 303 to 304, 304 to 305 and 305 to 306, is computed in turn.
- block 110 it is checked whether the whole signal 200 has been examined. If the whole signal 200 has been examined, we proceed to block 112 where the method ends. If the whole signal 200 has not been examined yet, we return to block 102 where the period 322 following the examined period 320 will be set under examination.
- a real signal may contain e.g. 8000 samples per second.
- the starting point of the next period 322 is the sample 360 that follows the last sample 306 of the preceding period 320.
- the signal 200 is examined in periods 320, 322 that follow each other in time. Problems are caused by controlling of the limits: a rhythmic se- ries may continue beyond the limits between the periods 320, 322. This can, however, be controlled by comparing the information of the preceding period 320 with that of the following period 322.
- the starting point of the next period 322 is the last extreme value sample 306 of the rhythmic series found in the pre- ceding period 320.
- the periods 320, 322 overlap to some extent, which makes the examination of the signal 200 slower, but may simplify the controlling of the limits.
- the starting point of the next period 322 is after the first sample 362 of the preceding period 320.
- the peri- ods 320, 322 may overlap as much as desired, regardless of whether rhythmic series were found or not in the processing of the preceding period 320.
- the second period 322 is searched for six extreme signal values 311 , 312, 313, 314, 315, 316.
- the temporal distances between these extreme signal values 311 , 312, 313, 314, 315, 316 are denoted by 340, 342, 344, 346, 348.
- Figure 3B includes a rhythmic series which con- tinues beyond two periods 320, 322 because the temporal distance 350 between the last extreme value sample 306 of the last rhythmic series found in the preceding period 320 and the first extreme value sample 311 of the new period 322 differs at most by a preset limit from the distances 334, 336, 338, 340 between the other extreme value samples 303, 304, 305, 306, 311 , 312 belonging to the series found.
- the rhythmic series found consists of six extreme value samples 303, 304, 305, 306, 311 , 312.
- a second rhythmic series is also found in the second period 322, the series consisting of extreme value samples 314, 315, 316 between which the temporal distances 346 and 348 are equal. It is also interesting to note that a rhythmic series may also consist of both highest values 314, 316 and lowest values 315.
- the series found can be processed further according to the prior art to find out whether it constitutes one or more longer basic series. In the further processing it can also be analysed whether a real series was found, because a series may be e.g. too short considering the character of the signal to be examined.
- Figure 5 illustrates a second preferred principal embodiment of the invention. The steps of this principal embodiment are shown in Figure 1C in which the function of block 104 is performed in blocks 140, 142 and 144.
- Figure 5 corresponds to Figure 2A, i.e. the signal to be examined has been placed in the system of coordinates, in which case the x-axis represents time T and the y-axis the signal value V at any given moment.
- the method of Figure 1C is similar to the method shown in Figure 1A, except for the following refinements and changes.
- block 140 the signal is searched for all local extreme value samples, i.e. local maximums (or mini- mums), in other words all the points at which the direction of the signal values changes.
- these maximums are marked with a black dot 520.
- block 146 is used for repeating the steps of blocks 142, 144, 106 and 108 until a rhythmic series is found or until it is concluded that a rhythmic series can no longer be found.
- each remaining extreme value sample is evaluated so that the extreme value sample having an ascending relation to the preceding extreme value sample receives a symbol indicating ascent, and the extreme value sample having a descending relation to the preceding extreme value sample receives a symbol indicating descent.
- the extreme value samples found are examined to find out what their relation to the preced- ing extreme value sample is. If the value of the maximum exceeds the value of the preceding maximum, the maximum is marked with a plus sign.
- the maximum is marked with a minus sign.
- the first maximum to be examined is given a plus sign. All the maximums of the period to be examined are processed as described above. In the first round the maximums thus receive the following signs: +-+-
- the extreme value samples that were given one of the symbols are removed from processing, i.e. in our example those maximums that received a plus sign are selected for examination for the second round 508 and the extreme value samples that received a minus sign are removed from processing. In Figure 5 this is illustrated by circles around the plus signs.
- the functions of blocks 106, 108 described earlier are performed, i.e. it is checked whether the extreme value samples marked with plus signs form a rhythmic series.
- the search for a rhythmic series should be continued. If a rhythmic series with a sufficiently good quality has been found, the search is not necessarily continued. On the other hand, if it is noticed that a rhythmic series can no longer be found, we proceed to block 112.
- the quality of a rhythmic series can be measured e.g. with the average magnitude of the differences between the temporal distances.
- the maximums that were given a plus sign are selected for the third round 510 from the second round.
- the maximums selected from among the maximums of the second round 508 have been circled.
- the selected eight maximums are again processed according to the rules described above, which yield the following signs: +-+-++-+. This means that a rhythmic series was not found in the third round, either.
- the method of the invention continues normally from block 106.
- the distance 502 between the originally first maximum sample 500A and the eight 500B maximum sample, the distance 504 between the eight 500B and the sixteenth 500C maximum sample, and the distance between the sixteenth 500C and the twenty-second 500D maximum sample are compared with one another. Since these temporal distances 502, 504, 506 differ from one another only by a preset limit, the extreme value samples 500A, 500B, 500C and 500D in question constitute a rhythmic series according to block 108.
- the second principal embodiment described above can also be implemented in a memory saving manner by originally inserting the samples into a table where each table index indicates the temporal location of the sample. For example, a sample with a length of 100 milliseconds provides 8000 points to be examined, each of the points requiring 16 bits, i.e. 128 kilobits of the storing capacity. From this point onwards the analysis described requires a two-dimensional table where one bit indicates the sign of the maximum, e.g. zero indicates the minus sign and one the plus sign. The second column of the table includes a pointer to the index corresponding to the maximum of the original table with the length of 128 kilobits.
- Figure 4 illustrates an apparatus applying the method according to the invention. Only the relevant parts of the apparatus are described here, which are the input 400 of the signal to be examined, sampling means 402 for taking samples from the signal at a certain frequency 202, and microprocessor 404 for processing the samples employing the method described above.
- the invention is preferably implemented by means of software, in which case the invention requires functions in the microprocessor, the microprocessor 404 being consequently arranged to: divide the signal into at least one period, find local extreme values of the samples, compute the temporal distance between each two adjoining extreme value samples in turn, conclude: if at least two adjoining temporal distances differ from each other at most by a preset limit, the extreme value samples used for com- puting these distances constitute a rhythmic series.
- the invention can be implemented not only by means of software but also by means of asic (application specific integrated circuit) or separate logic consisting of hardware parts.
- the invention can also be implemented by storing the program in a memory means that can be read by a general- purpose computer.
- the computer program stored in the memory means performs the method of evaluating the rhythmicity of a digital signal composed of samples.
- the memory means may be e.g. a computer hard disk, disk, CD-ROM, or any other memory means in which a computer program can be stored and from which a computer can read the program and perform it.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU45724/00A AU4572400A (en) | 1999-05-18 | 2000-05-17 | Method of evaluating the rhythmicity of a digital signal composed of samples |
EP00927291A EP1210710A1 (en) | 1999-05-18 | 2000-05-17 | Method of evaluating the rhythmicity of a digital signal composed of samples |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI991132A FI991132A (en) | 1999-05-18 | 1999-05-18 | The method is to investigate the rhythmicity of a digital signal formed from samples |
FI991132 | 1999-05-18 |
Publications (1)
Publication Number | Publication Date |
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WO2000070602A1 true WO2000070602A1 (en) | 2000-11-23 |
Family
ID=8554684
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FI2000/000445 WO2000070602A1 (en) | 1999-05-18 | 2000-05-17 | Method of evaluating the rhythmicity of a digital signal composed of samples |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1210710A1 (en) |
AU (1) | AU4572400A (en) |
FI (1) | FI991132A (en) |
WO (1) | WO2000070602A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6876965B2 (en) | 2001-02-28 | 2005-04-05 | Telefonaktiebolaget Lm Ericsson (Publ) | Reduced complexity voice activity detector |
CN111657905A (en) * | 2020-06-23 | 2020-09-15 | 中国医学科学院生物医学工程研究所 | Feature point detection method, device, equipment and storage medium |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3979557A (en) * | 1974-07-03 | 1976-09-07 | International Telephone And Telegraph Corporation | Speech processor system for pitch period extraction using prediction filters |
US4802225A (en) * | 1985-01-02 | 1989-01-31 | Medical Research Council | Analysis of non-sinusoidal waveforms |
EP0334023A2 (en) * | 1988-03-25 | 1989-09-27 | Telenorma Gmbh | Method for speech signals detection |
US5644678A (en) * | 1993-02-03 | 1997-07-01 | Alcatel N. V. | Method of estimating voice pitch by rotating two dimensional time-energy region on speech acoustic signal plot |
WO1999010879A1 (en) * | 1997-08-25 | 1999-03-04 | Telefonaktiebolaget Lm Ericsson | Waveform-based periodicity detector |
GB2330727A (en) * | 1997-10-24 | 1999-04-28 | Mitel Corp | Tone and periodical signal detection |
-
1999
- 1999-05-18 FI FI991132A patent/FI991132A/en not_active IP Right Cessation
-
2000
- 2000-05-17 AU AU45724/00A patent/AU4572400A/en not_active Abandoned
- 2000-05-17 WO PCT/FI2000/000445 patent/WO2000070602A1/en not_active Application Discontinuation
- 2000-05-17 EP EP00927291A patent/EP1210710A1/en not_active Withdrawn
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3979557A (en) * | 1974-07-03 | 1976-09-07 | International Telephone And Telegraph Corporation | Speech processor system for pitch period extraction using prediction filters |
US4802225A (en) * | 1985-01-02 | 1989-01-31 | Medical Research Council | Analysis of non-sinusoidal waveforms |
EP0334023A2 (en) * | 1988-03-25 | 1989-09-27 | Telenorma Gmbh | Method for speech signals detection |
US5644678A (en) * | 1993-02-03 | 1997-07-01 | Alcatel N. V. | Method of estimating voice pitch by rotating two dimensional time-energy region on speech acoustic signal plot |
WO1999010879A1 (en) * | 1997-08-25 | 1999-03-04 | Telefonaktiebolaget Lm Ericsson | Waveform-based periodicity detector |
GB2330727A (en) * | 1997-10-24 | 1999-04-28 | Mitel Corp | Tone and periodical signal detection |
Non-Patent Citations (1)
Title |
---|
HYUNG LAE KIM ET AL.: "A study on pitch detection using the local peak and valley for Korean speech recognition", TENCON'96. PROCEEDINGS., 1996 IEEE TENCON. DIGITAL SIGNAL PROCESSING APPLICATIONS, vol. 1, 1996, pages 107 - 112, XP010236836 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6876965B2 (en) | 2001-02-28 | 2005-04-05 | Telefonaktiebolaget Lm Ericsson (Publ) | Reduced complexity voice activity detector |
CN111657905A (en) * | 2020-06-23 | 2020-09-15 | 中国医学科学院生物医学工程研究所 | Feature point detection method, device, equipment and storage medium |
Also Published As
Publication number | Publication date |
---|---|
AU4572400A (en) | 2000-12-05 |
EP1210710A1 (en) | 2002-06-05 |
FI991132A0 (en) | 1999-05-18 |
FI991132A (en) | 2000-11-19 |
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