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EP0337868B1 - Verfahren und Einrichtung zur Signalunterscheidung - Google Patents

Verfahren und Einrichtung zur Signalunterscheidung Download PDF

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Publication number
EP0337868B1
EP0337868B1 EP19890400978 EP89400978A EP0337868B1 EP 0337868 B1 EP0337868 B1 EP 0337868B1 EP 19890400978 EP19890400978 EP 19890400978 EP 89400978 A EP89400978 A EP 89400978A EP 0337868 B1 EP0337868 B1 EP 0337868B1
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EP
European Patent Office
Prior art keywords
signal
time
amplitude
distribution
amplitudes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19890400978
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English (en)
French (fr)
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EP0337868A3 (en
EP0337868A2 (de
Inventor
Michel Ruiz
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Telediffusion de France ets Public de Diffusion
Original Assignee
Telediffusion de France ets Public de Diffusion
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Publication of EP0337868A2 publication Critical patent/EP0337868A2/de
Publication of EP0337868A3 publication Critical patent/EP0337868A3/fr
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Publication of EP0337868B1 publication Critical patent/EP0337868B1/de
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
    • G10L25/78—Detection of presence or absence of voice signals

Definitions

  • the present invention relates to discrimination between signals, in particular for recognizing the presence of a program audio-frequency signal having a determined bandwidth in an input signal capable of being affected by substantially stationary noise.
  • the invention finds a particularly important application in broadcasting or transmission networks having centers to which arrive and from which signals carrying broadcasting or television programs in more or less significant number depending on geographic location and importance of the center in the network.
  • the larger centers are generally operated by an agent on site. But others are tele-operated from a central station. In all cases, incidents occurring with signals distributed by a center must be detected as quickly as possible, so that the measures necessary to ensure continuity and quality of service can be taken.
  • a particularly serious incident is the accidental interruption of the program, which must be detected very quickly. It is also desirable to monitor the parameters influencing the quality of broadcasting and transmission throughout the routing of programs to the listener. In automated centers, verification can only be ensured by a local automated system, which, depending on its degree of development, will command the required maneuvers or will limit itself to transmitting an alarm to a central station, hence the required instructions (go to an emergency route, diversion, ...) will be provided to the local machine.
  • the usual detection criteria are based on the comparison between the amplitude of the transmitted or broadcast signal and a threshold: if the signal present has an amplitude below a certain predetermined threshold, it is considered that there is a defect and it is concluded that the absence of an audio signal if the fault persists beyond a determined period.
  • the present invention aims to provide a method and a device for recognizing the presence of a program audio-frequency signal (the term audio does not imply that these are signals representing sounds) which meet the requirements of practice better than those previously known, in particular by rendering them to a large extent free from the disadvantages of previous systems; it aims in particular to determine, with a high degree of safety, the interruptions of the program signal.
  • the invention is based on the observation that the program signals have stochastic properties which differentiate them from the noise created by the most frequent parasitic sources. For stations placed at a fixed station, for example, the noise characteristics are statistically unchanging or at least change slowly over time, unlike the characteristics of an audio-program frequency signal. In other words, noise generally has properties of ergodicity and stationarity which are not those of a useful signal.
  • the invention therefore proposes a discrimination method according to claim 1.
  • the sampling frequency is advantageously at least equal to the Shannon frequency when it is also desired to perform an analysis of the signal, for example to determine its quality.
  • the above-defined method involves a decision in the sense of statistics and uses variations in the distribution function of the amplitude values or, in a more elaborate version, variations in the distribution of these values as a decision criterion to detect the absence of a program signal, caused for example by a connection break upstream of the location where the detection is carried out.
  • the sampling frequency of the input signal can be relatively low. But it is also possible to implement the method for determining in addition a certain number of parameters representative of the quality of the signal and of its characteristics, which makes it possible in particular to determine either the alterations that the signal may undergo during its subsequent delivery to the recipient while remaining of acceptable quality, or corrections to be made. In this case, sampling should be done at least at the Shannon frequency.
  • the invention also provides a device making it possible to implement the above-defined method, according to claim 9.
  • the device is intended to continuously monitor the presence of three analog program signals and a digital signal, these numbers not being limiting.
  • Each analog signal is assigned a channel comprising, from the corresponding source, a coupler stage 10, an input stage 12 intended to ensure the impedance matching, the symmetry and the gain control of the channel, and a blocking sampler 14.
  • the input stage can moreover ensure band filtering and pre-emphasis of the audio-frequency signal when necessary. It will first be assumed that the blocking sampler operates at least at the Shannon frequency (for example at 32 kHz or 48 kHz in the case of a signal having a bandwidth between 40 Hz and 15 kHz). A lower sampling frequency can be adopted when simply trying to provide an alarm in the absence of an audio signal.
  • the output signals of the blocking samplers 14 of all the analog channels are applied to an analog multiplexer 16 which can be provided either for interleaving them, or for processing successively the different ways. They attack an analog / digital converter 18 which converts the amplitude of each sample into a byte representing this amplitude in digital form.
  • the sample-and-hold units 14, the analog multiplexer 16 and the analog / digital converter are clocked by a sequencer 20 provided with a clock and supplying, on an output 21, control signals to select one of the channels at any time.
  • the corresponding channel 22 is applied to a digital data decoder 24 providing the digital value of the amplitude of the samples in a form compatible with that provided by the analog / digital converter (CAN) 18.
  • a digital multiplexer 26 receives the digital output signals from the CAN 18 and from the decoder 24 and supplies them on a common output 28. This digital multiplexer receives control signals on the one hand from the sequencer 20, on the other hand part of the decoder 24 which performs clock recovery for this purpose. If the signals to be monitored are all analog, it is possible to dispense with components 24 and 26.
  • the processing of the signals downstream from the digital multiplexer 26 is the same regardless of the channel from which they originate and regardless of the chosen mode of detection of the absence of signal (determination of the variation in distribution of the amplitude or variation of the amplitude distribution function).
  • a sorting and storage operation is carried out, comparable to a multi-channel analysis. All the samples taken on the same channel during a constant time interval ⁇ t are divided into a certain number n of channels spaced by a determined pitch (1 dB for example) and the samples accumulated in each channel during the time ⁇ t are counted.
  • the multichannel analyzer 30 can include a set of comparators 32 and a random access memory 34. The comparators can be reduced to a programmable transcoding network.
  • Each of the n channels is assigned a corresponding address location in memory 34.
  • the zero order channel corresponds to the minimum amplitude Amin that we want to take into account.
  • Channel n-1 corresponds to the maximum amplitude Amax.
  • channel 0 52 channels spaced by 1 dB;
  • channel 0 may correspond to samples of amplitude equal to or less than -30 dBu.
  • Channel 51 will then correspond to samples of amplitude equal to or greater than +22 dBu.
  • the multichannel analysis can be carried out very simply using a programmable transcoding read-only memory 32 which corresponds, to each digital sample value, the address of one of the n channels.
  • the increment order is sent by a circuit 38 in a conventional manner.
  • each memory location contains a number indicating the number of times the signal sample has had a determined amplitude. There is thus a distribution of the amplitudes of the signal during the recording time ⁇ t, which can for example be of the type shown in FIG. 2 and this for each signal to be supervised.
  • the processing for detecting the absence of a signal is provided by a computer 36.
  • the memory 34 must be addressable in read and write by the read only memory 32, in read and write by the computer 36. It will first be assumed that the processing aims to determine the presence or absence of a signal by taking into account the distribution of the amplitudes.
  • the amplitude distribution and the average amplitude frequently vary over time.
  • the amplitude distribution and the average amplitude frequently vary over time.
  • values between 0.8 s and 5 s can be frequently adopted for the time intervals ⁇ t, advantageously approximately 1 s for spoken programs and approximately 3 s for music programs.
  • the detection by comparison of the distribution of the amplitudes could for example be done by determination, by the computer 36, of the correlation factor between several successive records, for example between two distributions stored in memory 34 for two successive time intervals ⁇ t.
  • the distribution functions F j + 1 and F j are compared. If the absolute value of difference between them (or between their representations in the form of percentages of time) is less than a determined threshold, the computer signals a fault (indication of pre-alarm). Expressed as a percentage of time, the threshold can often be 0.5%. However, it may be necessary to increase it in an environment of impulse noise up to approximately 2% to avoid absence of detection.
  • the computer proceeds to the processing of the following records to calculate F j + 1 and F j + 2 .
  • the computer 36 If the fault persists for a given time (for example ten consecutive seconds) the computer 36 emits an absence of modulation alarm.
  • the decision criterion is twofold and it is represented by the flowchart: This second, more secure solution does not significantly complicate the program and will generally be used. In both cases the value of the threshold x is kept as long as a fault is reported.
  • Figure 3 shows an example of how x is determined for a particular signal.
  • the first measurement is supposed to be made between instants t0 and t1.
  • the maximum amplitude is then A1.
  • a second embodiment making it possible to reduce the calculation time consists in calculating the percentage of time during which X has been greater than the value x over the time interval ⁇ t.
  • the successive values thus obtained are treated by the same type of comparison as F j (X) and F j + 1 (X) .
  • This function can be used to develop other types of alarm, for example an overmodulation alarm in the case where the program signal has too large an amplitude, and leads to overmodulation.
  • the computer can also be provided to differentiate a noise from a sinusoidal signal, for example from a measurement or chain alignment signal, by analyzing the distribution of the amplitudes: it suffices in this case to compare the distribution of amplitude with stored distributions corresponding to the sinusoidal signals capable of being transported.
  • the maximum amplitude of the signal can be used during the successive ⁇ t intervals as a criterion.
  • the alarm signals can be transmitted on a link of any kind, in particular wired or wireless.

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  • Engineering & Computer Science (AREA)
  • Computational Linguistics (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Human Computer Interaction (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)

Claims (9)

  1. Verfahren zum Erkennen der Anwesenheit eines instationären Audio-Frequenzprogrammsignals in einem im wesentlichen stationäres Rauschen aufweisenden Eingangssignal, gemäß welchem: das Eingangssignal abgetastet wird; die Abtastwerte während aufeinanderfolgender Zeitintervalle festgelegter Dauer einer Amplitudenanalyse unterzogen werden, wobei die Dauer dazu ausreicht, in jedem Zeitintervall eine signifikante Amplitudenverteilung zu erhalten; und die für aufeinanderfolgende Zeitintervalle erhaltenen Amplitudenverteilungen, oder einfach die diese repräsentierenden Verteilungsfunktionen der Amplitudenwerte verglichen werden, um die Anwesenheit des Programms zu identifizieren durch Verwendung der stochastischen Eigenschaften des Programmsignals, dessen Amplitudenverteilung und mittlere Amplitude stark mit der Zeit variieren.
  2. Verfahren nach Anspruch 1, bei welchem die Analyse darin besteht, die maximale Amplitude während der Zeitintervalle zu bestimmen und ein Programmsignal durch die Tatsache zu identifizieren, daß die Variationen der maximalen Amplitude in aufeinanderfolgenden Zeitintervallen größer sind als ein gegebener Wert.
  3. Verfahren nach Anspruch 1, bei welchem der Vergleich darin besteht, die Verteilungsfunktion der Amplituden durch Multikanalanalyse zu bestimmen und ein Programmsignal durch die Tatsache zu identifizieren, daß die Variationen der Verteilungsfunktion der Amplituden in aufeinanderfolgenden Zeitintervallen größer sind als ein gegebener Wert.
  4. Verfahren nach Anspruch 3, bei welchem die Verteilungsfunktion der Amplituden von den Prozentwerten der Zeit in jedem Intervall gebildet ist, während der die Amplitude größer (oder kleiner) als eine bestimmte Schwelle ist.
  5. Verfahren nach Anspruch 4, bei welchem die Schwelle fest ist.
  6. Verfahren nach Anspruch 4, bei welchem die Schwelle für ein Intervall festgelegter Zeitdauer durch den Maximalwert der Amplitude des Signals im vorhergehenden Zeitintervall verringert um einen festen, zwischen 3 und 6 dB liegenden Wert bestimmt ist.
  7. Verfahren nach Anspruch 6, bei welchem der Wert der Schwelle bei Fehlererfassung beibehalten wird bis ein Alarm auf die Erfassung einer vorbestimmten Anzahl von Fehlern in aufeinanderfolgenden Zeitintervallen folgend ausgelöst wird.
  8. Verfahren nach einem der vorhergehenden Ansprüche, im Hinblick auf die Qualitätsanalyse des Signals, bei welchem Verfahren das Signal mit einer Frequenz abgetastet wird, welche mindestens gleich der Shannon-Frequenz ist.
  9. Vorrichtung zum Erkennen der Anwesenheit eines Audio-Frequenzprogrammsignals mit einer festgelegten Bandbreite in einem stationäres Rauschen aufweisenden Eingangssignal, umfassend
    - Mittel zum Abtasten des Eingangssignals,
    - Multikanalanalysemittel (30), welche die Verteilung der Amplituden des Signals speichern, die von den Mitteln zum Antasten in einem festgelegten Zeitintervall geliefert werden, und
    - Berechnungsmittel (36), welche den Vergleich der durch den Multikanalanalysator in zwei aufeinanderfolgenden Zeitintervallen gespeicherten Verteilung ermöglichen sowie das Aussenden eines Alarmsignals für den Fall, daß der Vergleich den stationären Charakter des Eingangssignals offenbart.
EP19890400978 1988-04-12 1989-04-10 Verfahren und Einrichtung zur Signalunterscheidung Expired - Lifetime EP0337868B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8804824A FR2629964B1 (fr) 1988-04-12 1988-04-12 Procede et dispositif de discrimination de signal
FR8804824 1988-04-12

Publications (3)

Publication Number Publication Date
EP0337868A2 EP0337868A2 (de) 1989-10-18
EP0337868A3 EP0337868A3 (en) 1990-10-24
EP0337868B1 true EP0337868B1 (de) 1993-12-15

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EP19890400978 Expired - Lifetime EP0337868B1 (de) 1988-04-12 1989-04-10 Verfahren und Einrichtung zur Signalunterscheidung

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EP (1) EP0337868B1 (de)
DE (1) DE68911355T2 (de)
FR (1) FR2629964B1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6570991B1 (en) 1996-12-18 2003-05-27 Interval Research Corporation Multi-feature speech/music discrimination system
EP1172020B1 (de) 1999-02-05 2006-09-06 Hearworks Pty Ltd. Tonprozessor zur adaptiven dynamikbezeichsverbesserung
US7366315B2 (en) 1999-02-05 2008-04-29 Hearworks Pty, Limited Adaptive dynamic range optimization sound processor

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1044353B (it) * 1975-07-03 1980-03-20 Telettra Lab Telefon Metodo e dispositivo per il rico noscimento della presenza e.o assenza di segnale utile parola parlato su linee foniche canali fonici
JPS5876899A (ja) * 1981-10-31 1983-05-10 株式会社東芝 音声区間検出装置

Also Published As

Publication number Publication date
FR2629964B1 (fr) 1991-03-08
DE68911355D1 (de) 1994-01-27
FR2629964A1 (fr) 1989-10-13
DE68911355T2 (de) 1994-07-21
EP0337868A3 (en) 1990-10-24
EP0337868A2 (de) 1989-10-18

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