CN101697603B - Method and device for measuring phase difference between left channel and right channel - Google Patents
Method and device for measuring phase difference between left channel and right channel Download PDFInfo
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Abstract
The invention relates to a method and a device for measuring a phase difference between a left channel and a right channel. The method comprises the following steps of generating a tested signal with the frequency of F and a ruler signal with the frequency of F1=(n/(n-1))*F by using a signal generator; respectively inputting the tested signal with a standard cycle phase difference of delta phi 0 and the ruler signal to input ports of the left channel and the right channel of equipment to be tested; displaying output signals processed by the equipment to be tested by using a dual-trace oscilloscope and finding out that when the ruler signal has m cycles away from the standard cycle and the phase difference between the ruler signal and the tested signal is 0, the phase difference delta phi between the output tested signal and the ruler signal is equal to m/n*360 DEG, wherein a symbol thereof takes positive in right avertence and takes negative in left avertence and the phase difference of the left channel and the right channel is delta phi-delta phi 0. The device comprises the equipment to be tested, the test signal generator of the phase difference between the left channel and the right channel and the dual-trace oscilloscope. The invention can realize the measurement of the phase difference between the left channel and the right channel by utilizing the signal generator loaded with testing signals, and the dual-trace oscilloscope, thus the measurement cost is low and the accuracy is high.
Description
Technical field
The present invention relates to a kind of method and apparatus of measurement, particularly a kind of method and apparatus of measuring interchannel phase difference.
Background technology
When audio frequency apparatus develops into dual track by monophony, weigh the index of sound quality except the index of each independent sound channel, increased by three to left and right acoustic channels between the relevant index of difference, i.e. left and right acoustic channels gain inequality, phase difference and crosstalk.Gain inequality still can first be measured respectively the output level of each sound channel with crosstalking, then obtains by certain computing.The signal that only phase difference must detect two sound channels simultaneously just can record their relative difference.Available dual trace oscilloscope detects the signal waveform of two sound channels simultaneously in principle, compares and obtains the difference in phase place, and such comparison, although the existence of discernable phase difference can not obtain the concrete numerical value of phase difference.Due to the index very high (≤5 °) of equipment, to such an extent as to judge that whether qualified also difficulty accomplishes.The instrument that is used for specially measuring audio signal quality is " audio analyzer ", and China can produce this kind equipment, and has the relevant standard of this equipment, but is only applicable to monophony, does not possess the function of measure phase difference.Only have many (two) channel audio analyzer of several import could measure this project, price is extremely expensive, has greatly increased testing cost.Therefore urgently need to find to measure interchannel phase difference new method of measuring and the device that cost is low, precision is high.
Summary of the invention
For addressing the above problem, the invention provides a kind of method and apparatus of measuring the measurement interchannel phase difference that cost is low, precision is high.
The present invention measures the method for interchannel phase difference, wherein: comprise step:
A, the measured signal and the frequency that with signal generator generated frequency, are F are the scale signal of F1=(n/ (n-1)) * F;
B, reference period phase difference are ΔΦ
0measured signal and the scale signal input port of inputting respectively Devices to test left and right acoustic channels, described ΔΦ
0be 0 or known numeric value;
C, the output signal with dual trace oscilloscope demonstration after Devices to test is processed, finding in scale signal is 0 with reference period at a distance of m cycle and measured signal phase difference, the measured signal and the scale signal phase difference ΔΦ=m/n*360 ° that export, its symbol right avertence is just being got, left avertence is got negatively, and the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
The present invention measures the method for interchannel phase difference, wherein: the antinode in the reference period of scale signal is provided with initial point mark.
The present invention measures the method for interchannel phase difference, wherein: initial point is labeled as one of height difference of high frequency mark on waveform, breach, projection, amplitude.
The present invention measures the method for interchannel phase difference, wherein: the frequency F of measured signal is 997Hz.
The present invention measures the method for interchannel phase difference, wherein: n equals one of 90,180,360,720.
The present invention measures the method for interchannel phase difference, wherein: Devices to test is dual-channel audio amplifier or the system that consists of audio coding unit, Multiplexing Unit, chnnel coding unit, modulate emission unit, receiving demodulation unit, channel-decoding unit, demultiplexing unit, audio decoding unit.
The present invention measures the method for interchannel phase difference, wherein: Devices to test is multichannel equipment, F1 is placed in to a certain particular channel, other sound channel is put F, with dual trace oscilloscope, can directly measure other sound channel with respect to the phase difference of particular channel, they are subtracted each other to the phase difference that can obtain between them with respect to the phase difference tape symbol of particular channel separately.
The present invention measures the device of interchannel phase difference, comprises Devices to test, wherein, also comprises:
Interchannel phase difference measuring signal generator, the measured signal that is F for generated frequency and frequency are the scale signal of F1=(n/ (n-1)) * F, reference period phase difference is ΔΦ
0measured signal and the scale signal input port of inputting respectively Devices to test left and right acoustic channels, described ΔΦ
0be 0 or known numeric value;
Dual trace oscilloscope, be connected to the circuit output end of Devices to test left and right acoustic channels, for showing the output signal after Devices to test is processed, finding in scale signal is 0 with reference period at a distance of m cycle and measured signal phase difference, the measured signal and the scale signal phase difference ΔΦ=m/n*360 ° that export, its symbol right avertence is just being got, left avertence is got negatively, and the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
The present invention measures the device of interchannel phase difference, comprises audio decoding apparatus to be measured, wherein, also comprises:
The interchannel phase difference measuring signal generator of coding, the measured signal that is F for generated frequency and frequency are the scale signal of F1=(n/ (n-1)) * F, reference period phase difference is ΔΦ
0measured signal and scale signal input respectively audio coder, the output signal of audio coder is inputted the input port of audio decoding apparatus to be measured;
Dual trace oscilloscope, be connected to the circuit output end of audio decoding apparatus left and right acoustic channels to be measured, for showing the output signal after audio decoding apparatus to be measured is processed, finding in scale signal is 0 with reference period at a distance of m cycle and measured signal phase difference, the measured signal and the scale signal phase difference ΔΦ=m/n*360 ° that export, its symbol right avertence is just being got, left avertence is got negatively, and the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
The present invention measures the device of interchannel phase difference, wherein: audio coder is compounded in TS stream encoder or various numeral and analogue audio frequency encoder.
The method and apparatus that the present invention measures interchannel phase difference is used the signal generator of above-mentioned test signal and the measurement that dual trace oscilloscope can be realized interchannel phase difference is housed, and therefore measures that cost is low, precision is high.
Accompanying drawing explanation
Fig. 1 is the waveform of left and right acoustic channels frequency while being all F;
Fig. 2 is that A sound channel is F1, and B sound channel is F, the situation during without phase difference;
Fig. 3 is that A sound channel is F1, and B sound channel is F, and has the situation of small phase difference;
Fig. 4 is the fundamental measurement circuit block diagram of the present invention's device of measuring interchannel phase difference;
Fig. 5 is audio decoding apparatus interchannel phase difference measuring circuit block diagram;
Fig. 6 is that basis and signal waveform are determined characteristic point position schematic diagram;
Fig. 7 determines characteristic point position schematic diagram according to the symmetry of F, the overlapping waveform of F1.
Embodiment
The method and apparatus of the present invention being measured to interchannel phase difference below in conjunction with Figure of description is described further.One, the principle of interchannel phase difference method of measurement
Fig. 1 is the waveform (one of them sound channel made reverse process) of left and right acoustic channels frequency while being all F, if both phase differences are 0, trough and the antinode all align of (A sound channel) waveform under upper (B sound channel), if there is small phase difference ΔΦ (as shown in Figure 1) between them, trough and antinode be no longer alignment, and each period migration is but all identical.Because skew one-period is 360 °, side-play amount in 360 ° observes waveform estimate with operator entirely, therefore directly it is very difficult according to the size of skew, measuring ΔΦ, is difficult to the certainty of measurement that reaches higher, especially to observe positive and negative 5 ° more difficult with interior phase difference.
If the frequency of A sound channel is brought up to F1 slightly, make the interior F1 of n-1 cycle of B sound channel F have n cycle, be F1=(n/ (n-1)) * F, as shown in Figure 2, when reference period (, for comparing the cycle of both phase differences, being also the cycle at initial point place) phase difference is 0 o'clock, the antinode of the F1 of initial point place is alignd with the trough of F, to no longer align afterwards, and be offset increasing, until n the antinode of F1 just in time alignd with (n-1) individual trough of F.When reference period phase difference is ΔΦ, as shown in Figure 3, the antinode of initial point F1 and the trough of F have not just lined up, but can find F1 with initial point at a distance of the individual antinode of m (m=3 in figure) align with the trough of F (hereinafter referred to as characteristic point), because n the antinode of F1 is corresponding to 360 ° of phase shifts, m is corresponding to phase shift m/n 360 ° (ΔΦ=m/n*360 °).As can be seen here, as long as the initial point of F1 and F is marked, number goes out characteristic point has how many cycles from initial point, just can obtain the concrete angle of phase difference, and according to whose leading whose backwardness of the direction determining of displacement.We claim that F is measured signal, and F1 is scale signal.From analyzing above, the key point of this method of measurement is to substitute the small direct skew that is difficult to determine with the skew of determining characteristic point.Due to the skew of characteristic point with respect to direct skew " amplification " n doubly, make accurately to measure and become possibility.
It is to be noted, according to above-mentioned principle, measured signal and scale signal input Devices to test before reference period preferably phase difference be 0, now relatively ΔΦ=m/n*360 ° of the F1 of Devices to test output and F phase difference are exactly the phase difference of left and right acoustic channels, and its symbol right avertence is just being got, left avertence is got negative; If measured signal and scale signal reference period before input Devices to test is not 0, should be known numeric value ΔΦ yet
0if, measured signal and the scale signal phase difference ΔΦ=m/n*360 ° of now Devices to test output, its symbol right avertence is just being got, left avertence is got negatively, and the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
Two, the selection of test signal parameters
1) frequency F
Frequency F is often by measurement standard defined.By the standard of China, as external many standards, F is 997Hz.But say in principle any audio frequency that the desirable requirement of F is measured.
2) value of n
Say in principle, n is larger, and reading is more accurate.For example, get respectively n and equal 90,180,360 and the every variation 1 of 720, m, corresponding ΔΦ is 4 °, 2 °, 1 ° and 0.5 °.In fact, if n gets larger value, the difference between the waveform of different m is just too little, is difficult to determine the position of characteristic point, and the number also difficulty all the more of number that goes out waveform, on the contrary correct reading.N should and be convenient to reading according to precision and choose eclectically, as chosen 90,180,360 and 720 in the present invention.
3) section repeats
With reference to Fig. 2, continuous signal by one, described in the principle of interchannel phase difference method of measurement, in gauge point relativity shift, the number in contained cycle can be determined the number of contained 360 ° of phase difference, the part that less than is 360 °, by m, determined, so range can be ad infinitum large.But make oscilloscope catch initial point and stably the complete waveform of different two signals of display frequency be very difficult, be practically impossible in other words.Yet the range of requirement is in fact very little, such as index is in the situation of 5 °, within ± 10 °, read definite result, inform outside ± 10 ° phase difference surpass ± 10 ° met the demands.Therefore can use continuous signal, as long as choose the signal that comprises initial point and both sides some cycles thereof and it is constantly repeated just passable.The length of section is determined jointly by precision and range.
4) making of mark
The mark of counting initial point is indispensable, and when range is within 360 °, the relativity shift of initial point can not exceed 1 cycle, upper just passable as long as mark is made in scale signal F1.The effect of mark is only to make antinode and other general antinode as initial point to make a distinction, therefore can adopt any feasible mode, for example in Fig. 2 and Fig. 3, adopted high frequency mark, other all can be selected as the height of amplitude, breach/projection etc., and these marks are used general signal generator programming to realize.If wave period is too many between duplicate block, in every 10 antinodes in the both sides of F1 initial point, also can do secondary mark to facilitate the counting of m so, they should be distinguished to some extent with initial point mark certainly.
Three, test signal example
1, F is 997Hz (relevant criterion requirement);
2, get n=360, during m=1, ΔΦ=1 °;
3、F1＝n/(n-1)F＝999.777159Hz；
4, between duplicate block, get 25ms (repetition per second 40 times), interval central authorities are the antinode of F1, the trough of F, and F and F1 continue 24ms, approximately have 24 cycles (range can reach positive and negative 12 °), and respectively there is the gap of 0.5ms no signal front and back;
5, the normal amplitude of signal is 20dBFS (1/10 full scale), in the antinode of F1 initial point, there is a breach to serve as a mark, in the antinode of the 10th of both sides, also there is more shallow breach as secondary mark, and 1s has mark 1s unmarked, so both indicate origin position, and can judge again the vivid shape of waveform when unmarked.
Four, method of measurement
1, the connection of measuring circuit
Fig. 4 is the fundamental measurement circuit block diagram of the present invention's device of measuring interchannel phase difference; Phase difference is the input port of 0 test signal F1 and F right (R) two-way in a left side (L) of receiving respectively Devices to test.For example, with dual trace oscilloscope (RIGOL DS1102C), show the output signal after Devices to test is processed, the phase difference of measuring gained is the phase difference that Devices to test causes.
" Devices to test " in Fig. 4, conceptive general reference, it can be single equipment (for example dual-channel audio amplifier), also can be the system that combined by some unit (simplified and traditional differing) (complicated system as: the system that audio coding unit, Multiplexing Unit, chnnel coding unit, modulate emission unit---receiving demodulation unit, channel-decoding unit, demultiplexing unit, audio decoding unit form), but this combined system common trait is to have the import of two-way audio signal and two-way audio signal outlet.This method of measurement be applicable to any meet Devices to test described above (system) and do not relate to it specifically form, all adopt and meet the F1 of afore mentioned rules and F as test signal, with the skew of dual trace oscilloscope characteristic point, read the phase difference ΔΦ of output signal.When measurand is only in system under test (SUT) during certain unit, the phase difference of remaining element should guarantee to be 0 so, or should be at least given value ΔΦ
0, the phase difference of unit under test is ΔΦ or (ΔΦ-ΔΦ so
0).Sometimes, test signal is just being included in certain unit of measuring system, Fig. 5 is a kind of practical measuring system of measuring audio decoder, in figure, " the interchannel phase difference measuring signal generator of coding " is exactly in fact the interchannel phase difference test signal of afore mentioned rules and the combination of audio coder (for example audio coder in TS flow-generator or various numeral and analogue audio frequency encoder).
This method is also applicable to multichannel occasion.For example L (left side), C (in), R (right side), SL (left back), under the 5 sound channel occasions of SR (right back), F1 can be placed in to sound channel C, other 4 sound channel is put F, with dual trace oscilloscope, can directly measure L, R, SL, SR separately with respect to the phase difference of C, if will measure the phase difference between them, they being subtracted each other to (tape symbol) with respect to the phase difference of C separately can obtain.
2, by the poor concrete steps of waveform reading phase
1) exact connect ion and adjustment: by (the L output of dual track of F1 signal, the C output of 5 sound channels) connect oscilloscope A input, (the R output of dual track of F signal, the L/R/SL/SR output of 5 sound channels) connect oscilloscope B input, all the parameters such as correct adjusting is oscillographic synchronously, gain, position, to obtain stable two-way waveform.
2) read measurement result
(1) oscilloscope has the occasion that is added function
Now should preferentially start this function, on screen 3 waveforms as shown in Figure 6, they are respectively F and signal (F+F1), F1 from top to bottom, fine setting A or (with) gain of B passage, make with the wave-shape amplitude of signal minimum.Carefully judge the position of wave-shape amplitude minimum, as amplitude in a segment limit is all minimum, sentencing its mid point is amplitude minimum position, and this point is the position of characteristic point.The number of contained wave period between counting from initial point to characteristic point, be the numerical value of surveyed phase difference, unit is that " (360 °/n) " are (in embodiment, due to n=360, unit is just in time " 1 ° "), when characteristic point is on the right of initial point, the phase place of F is more leading than F1, get positive sign, otherwise for negative.If phase difference is larger, initial point is larger to the distance of characteristic point, just very not convenient with initial point reading, now characteristic point from certain secondary mark can be close to, take the reading of this secondary mark as just more convenient with reference to remaking corresponding correction.
(2) oscilloscope is without the occasion of the function being added
As shown in Figure 7, by try one's best broadening (as enabled broadening function) upper and lower waveform is stacked slightly of display waveform, the careful relatively symmetrical degree of each overlapping waveform, the most symmetrical (the level of line in crosspoint, the highest minimum point line is the most vertical) the position that is characteristic point, if any a plurality of overlapping waveforms, be all judged to the most symmetrically, their mid point is judged to be the position of characteristic point so.Move horizontally waveform position, number goes out characteristic point with respect to the wave period number of initial point skew, by above-mentioned same rule, determines measurement result.
3) reading of embodiment first
From Fig. 6's with waveform, to the right in 2.5 to 4.5 periodic regimes of initial point, it is minimum that wave-shape amplitude all shows, so judge that characteristic point is to initial point right avertence 3.5.Due to n=360 in embodiment, thereby phase difference is+3.5 °, and F is than F1 leading 3.5 °.
The waveform of careful interpretation Fig. 7, the symmetry of the 2nd, 3,4,5 overlapping waveforms is better, and as widened rear careful comparison, 3,4 symmetry are better again, and result is all characteristic point right avertence 3.5, and phase difference is+3.5 °, consistent with the above results.
In fact above-mentioned measured signal F, F1 generate by software numeral, and designed phase is poor is 3.74 °, and the error of measurement result is within 0.5 °, and also super only 1 ° of the worst evaluated error, reaches the requirement of actual use completely.Realized and measured that cost is low, precision is high, can measure with all purpose instrument the predeterminated target of interchannel phase difference.
Above embodiment is described the preferred embodiment of the present invention; not scope of the present invention is limited; design under the prerequisite of spirit not departing from the present invention; various distortion and improvement that the common engineers and technicians in this area make technical scheme of the present invention, all should fall in the definite protection range of claims of the present invention.
Claims (9)
1. a method of measuring interchannel phase difference, is characterized in that, comprises step:
A, the measured signal and the frequency that with signal generator generated frequency, are F are F1=(n/(n-1)) the scale signal of * F, wherein: n is the number of cycles of F1 waveform, and as counting starting point cycle be called reference period, the antinode place of reference period is provided with initial point mark, and measured signal F is poor with respect to the original phase of scale signal F1 is ΔΦ
0, described ΔΦ
0be 0 or known numeric value;
B, above-mentioned measured signal F and scale signal F1 are inputted respectively to the input port of Devices to test left and right acoustic channels;
C, the output signal with dual trace oscilloscope demonstration after Devices to test is processed, take (being initial point) centered by the scale signal criterion cycle to both sides, find the point of the trough antinode consistency from top to bottom (phase difference is 0) of measured signal waveform and scale signal waveform, this point is called characteristic point, number goes out characteristic point and initial point wave period number m apart, characteristic point initial point right side m get on the occasion of, otherwise m gets negative value, the measured signal of output is to scale signal phase difference ΔΦ=m/n*360 °, and the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
2. the method for measurement interchannel phase difference according to claim 1, is characterized in that: initial point is labeled as one of height difference of high frequency mark on waveform, breach, projection, amplitude.
3. the method for measurement interchannel phase difference according to claim 2, is characterized in that: the frequency F of measured signal is 997Hz.
4. the method for measurement interchannel phase difference according to claim 3, is characterized in that: n equals one of 90,180,360,720.
5. the method for measurement interchannel phase difference according to claim 4, is characterized in that: Devices to test is dual-channel audio amplifier or the system that consists of audio coding unit, Multiplexing Unit, chnnel coding unit, modulate emission unit, receiving demodulation unit, channel-decoding unit, demultiplexing unit, audio decoding unit.
6. the method for measurement interchannel phase difference according to claim 4, it is characterized in that: when Devices to test is multichannel equipment, the scale signal that is F1 by frequency is placed in a certain particular channel, frequency is that the measured signal of F is placed in other sound channel, with dual trace oscilloscope, can directly measure other sound channel with respect to the phase difference of particular channel, each sound channel is carried out to additive operation with respect to the phase difference of scale signal, obtain the phase difference between them.
7. a device of measuring interchannel phase difference, comprises Devices to test, it is characterized in that, also comprises:
Interchannel phase difference measuring signal generator, the test signal that is F for generated frequency and frequency are F1=(n/(n-1)) the scale signal of * F, original phase is poor is ΔΦ
0test signal and the scale signal input port of inputting respectively Devices to test left and right acoustic channels, described ΔΦ
0be 0 or known numeric value;
Dual trace oscilloscope, be connected to the circuit output end of Devices to test left and right acoustic channels, for showing the output signal after Devices to test is processed, take (being initial point) centered by the reference period of scale signal to both sides, find the point of the trough antinode consistency from top to bottom (phase difference is 0) of measured signal waveform and scale signal waveform, this point is called characteristic point, number goes out characteristic point and initial point wave period number m apart, characteristic point initial point right side m get on the occasion of, otherwise m gets negative value, the test signal of output is to scale signal phase difference ΔΦ=m/n*360 °, the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
8. measure a device for interchannel phase difference, comprise audio decoding apparatus to be measured, it is characterized in that, also comprise:
The interchannel phase difference measuring signal generator of coding, the measured signal that is F for generated frequency and frequency are F1=(n/(n-1)) the scale signal of * F, reference period phase difference is ΔΦ
0measured signal and scale signal input respectively corresponding audio coder, the output signal of audio coder is inputted the respective input mouth of audio decoding apparatus to be measured;
Dual trace oscilloscope, be connected to the circuit output end of audio decoding apparatus left and right acoustic channels to be measured, for showing the output signal after audio decoding apparatus to be measured is processed, take (being initial point) centered by the reference period of scale signal to both sides, find the point of the trough antinode consistency from top to bottom (phase difference is 0) of measured signal waveform and scale signal waveform, this point is called characteristic point, number goes out characteristic point and initial point wave period number m apart, characteristic point initial point right side m get on the occasion of, otherwise m gets negative value, the test signal of output is to scale signal phase difference ΔΦ=m/n*360 °, the phase difference of left and right acoustic channels is ΔΦ-ΔΦ
0.
9. the device of measurement interchannel phase difference according to claim 8, is characterized in that: described audio coder be compounded in TS stream encoder or various numeral and analogue audio frequency encoder in.
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| CN101330776A (en) * | 2007-06-21 | 2008-12-24 | 上海风格信息技术有限公司 | Method for reverse phase detection of audio signal left and right acoustic channels |
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| CN101330776A (en) * | 2007-06-21 | 2008-12-24 | 上海风格信息技术有限公司 | Method for reverse phase detection of audio signal left and right acoustic channels |
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