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JP2012130009

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DESCRIPTION JP2012130009
The present invention provides a speaker array that enables virtual surround rendering. A virtual
sound rendering audio device, wherein the virtual sound rendering audio device receives a first
plurality of audio channel signals and an up mixed output signal and an associated output
surround signal. An up-mixer and a surround renderer, the surround renderer receiving a second
plurality of audio channel signals, each of the second plurality of audio signals being combined
into an associated output surround signal A surround renderer for generating a plurality of
transducer signals, at least a portion of the second plurality of transducer signals being each
coupled to an associated upmixed output signal, Surround rendering audio device Nest. [Selected
figure] Figure 3
バーチャルサラウンドレンダリングのためのスピーカアレイ
[0001]
(Background) (1. FIELD OF THE INVENTION The present invention relates to virtual speaker
sound systems. More specifically, it relates to digital signal processing and speaker arrays that
render rear surround channels.
[0002]
(2. Related Art Generally, playing surround sound with only a few speakers employs a spatial
enhancement technique. Space enhancement techniques are now available from many different
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suppliers, which allow to play surround sound from several loudspeakers arranged in front of the
listener. Examples of such applications are home theater systems (without the need for rear
speakers to be installed), surround movies and computer games that render with small
transducers integrated into a multimedia monitor or laptop. Includes 3D sound playback. Usually
a very narrow sweet spot that does not allow the head to move much, strong imaging, off-axis
tonal distortion, phasicity felt when the listener turns the head and ear pressure Such an obvious
problem arises, so the listening experience is totally unconvincing.
[0003]
One approach to providing sarand sound with only a few speakers is to employ a multi-way
crosstalk canceller during spatial enhancement. However, this approach requires a high-order
inverse filter matrix to generate an accurate ear signal based on an accurate head model, which
may occur if the listener's head is not in the correct intended position. This results in the loss of
off-axis sound quality.
[0004]
If a conventional crosstalk canceller circuit is used prior to a crossover filter connecting two pairs
of transducers, a signal processing approach is applied. However, this approach limits success.
Because the crosstalk canceller filter is not optimized for either of the transducer pairs.
[0005]
Thus, there is a need for a speaker array that enables virtual surround rendering that improves
surround sound reproduction. In particular, it is desirable to improve both the error strength and
off-axis tone of virtual surround sound.
[0006]
SUMMARY In view of the above, a digital signal processor is provided to process stereo or
surround audio signals, render virtual surround using only the speakers arranged in front of the
listener, and move the head into motion. The result is a virtual surround sound that is error
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prone and has a low off-axis tone that is superior to the prior approach. The digital signal
processor includes a speaker array, a rear surround channel having the width and depth of a
stereo front channel extended by employing a crossover head primary head related filter, an up
mixing matrix, and an array of delay lines. Render against and generate early reflections. It is
understood that although the features mentioned above and the features described below can be
used only in the combination respectively indicated, they can also be used in other combinations
or alone without departing from the scope of the invention It should.
[0007]
Other devices, devices, systems, methods, features and advantages of the invention will be or will
become apparent to one with skill in the art upon examination of the following figures and
detailed description. It is intended that all such additional systems, methods, features, and
advantages be included within the description, be within the scope of the invention, and be
protected by the accompanying claims.
[0008]
For example, the present invention provides the following items. (Item 1) A virtual sound
rendering audio device, wherein the virtual sound rendering audio device is an upmixer, the
upmixer receives a first plurality of audio channel signals and an upmixing output signal And an
associated surround surround signal, wherein the surround renderer receives a second plurality
of audio channel signals, the second plurality of audio signals being associated with each other. A
surround renderer coupled to the output surround signal to generate a plurality of transducer
signals, at least a portion of the second plurality of transducer signals each being coupled to an
associated upmixed output signal Virtual Sarah including and Command rendering audio device.
(Item 2) The virtual surround rendering audio device according to the above item, wherein the
first plurality of audio channel signals include at least a left channel signal, a right channel signal,
and a center channel signal. 3. The virtual surround rendering audio system of any of the above
items, wherein the center channel signal is combined with both the right channel signal and the
left channel signal. (Item 4) The virtual surround rendering audio device according to any of the
above items, wherein the up-mixer includes a stereo width adjustment section and a distance
adjustment section. (Item 5) The virtual surround rendering audio device according to any of the
items, wherein the stereo width adjustment section includes a first negative crossing coefficient
parameter. 6. The virtual surround rendering audio device of any of the above items, wherein the
stereo width adjustment section further includes a second negative crossing coefficient
parameter associated with the associated output surround signal. 7. The virtual surround
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rendering audio device of any of the above items, wherein the stereo width adjustment section
further includes a shelf filter associated with each of the plurality of audio channel signals
received at the upmixer. 8. The virtual surround rendering audio device of any of the above
items, wherein the distance adjustment section includes delay parameters associated with each of
the output signal and the associated output surround signal.
The virtual surround rendering audio device of any of the above items, wherein each of the
delays has a respective amplitude parameter. (Item 10) The virtual surround rendering audio
device according to any of the above items, wherein the surround renderer further includes each
of the output surround signals separated and passed through a low pass filter and a high pass
filter. 11. The system of claim 11 further comprising: a first plurality of combiners, wherein the
first plurality of combiners subtracts the delayed output from each of the other low pass filters
from the output of the first low pass filter; Virtual surround rendering audio device according to
any of the above items. 12. The method of claim 12 further comprising a second plurality of
combiners, wherein the second plurality of combiners subtracts the crosstalk canceller output
from each of the high pass filters from the output of the first high pass filter, Virtual surround
rendering audio device according to any of the items. (Item 13) The virtual surround rendering
audio device according to any one of the above items, wherein the crossover frequency of the
crosstalk canceller is in the range of 500 Hz to 2000 Hz. 14. A method of virtual surround
rendering, the method comprising: receiving a first plurality of audio channel signals at an
upmixer; and in response to receiving the first plurality of audio channel signals. Generating an
up-mixed output signal and an associated output surround signal; receiving a second plurality of
audio channel signals in a surround renderer; receiving the second plurality of audio channel
signals in the surround renderer Combining each of the second plurality of audio channel signals
into an associated output surround signal, and generating a plurality of transducer signals,
wherein At least a portion of each of the And a step coupled to the singed output signal. (Item
15) The method of virtual surround rendering according to the above item, wherein the reception
of the first plurality of audio channel signals includes receiving at least a left channel signal, a
right channel signal, and a center channel signal. 16. The method of virtual surround rendering
according to any of the above items comprising combining the center channel signal to both the
right channel signal and the left channel signal.
17. The method of virtual surround rendering according to any of the above items, wherein the
upmixer includes a stereo width adjustment section and a distance adjustment section. 18. The
method of virtual surround rendering according to any of the above items, comprising applying a
first negative cross coefficient parameter to the first plurality of audio channel signals in the
width adjustment section. 19. The method of virtual surround rendering according to any of the
above items, further comprising applying the second negative crossing coefficient parameter
associated with the associated output surround signal. . 20. The virtual of claim 20, wherein the
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stereo width adjustment section further includes filtering each of the plurality of audio channel
signals received at the upmixer associated with the shelf filter. Surround rendering method. 21.
The method of virtual surround rendering according to any of the above items, wherein the
distance adjustment section comprises delaying each of the output signal and the associated
output surround signal by a delay parameter. 22. The method of virtual surround rendering
according to any of the above items, wherein each of the delays has a respective amplitude
parameter. 23. The method of virtual surround rendering according to any of the above items,
further comprising the surround renderer filtering each of the output surround signal after being
separated through a low pass filter and a high pass filter. . 24. Any of the above items, further
comprising subtracting the delayed output from each of the other low pass filters from the
output of the first low pass filter using the first plurality of combiners. Method of virtual
surround rendering as described. 25. The method of any of the above items, further comprising
subtracting the crosstalk canceller output from each of the high pass filters from the output of
the first high pass filter using a second plurality of combiners. Virtual surround rendering. (Item
26) The virtual surround rendering according to any of the items described above, wherein the
crossover frequency of the crosstalk canceller is in the range of 500 Hz to 2000 Hz.
[0009]
(Commentary) Virtual surround with two-way approach adopting primary head related model,
similar to interaural time difference localized and interaural level difference localized stimulation
in frequency band respectively, avoiding phantom imaging and excessive tone An approach and
device for the generation of sound was used.
[0010]
The description below can be better understood by referring to the following figures.
The components in the figures are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. In the figures, like reference numerals refer to
corresponding parts throughout the different views.
[0011]
FIG. 1 is a diagram of a loudspeaker array in accordance with an example implementation of the
present invention. FIG. 2 is a simplified block diagram of a digital signal processor in accordance
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with an example implementation of the present invention. FIG. 3 is a block diagram of a five
channel surround renderer provided in the digital signal processor of FIG. 2 coupled to the
speaker array of FIG. 1 in accordance with an example implementation of the present invention.
FIG. 4 is a block diagram of the surround renderer of FIG. 3 in accordance with an example
implementation of the present invention. FIG. 5 is a graph of the summed response at the central
portion and 12 degrees off-axis of the five-channel surround renderer of FIG. 3 according to an
example of this implementation. FIG. 6 is a block diagram of the two in four out up mixer of FIG.
3 in accordance with an example implementation of the present invention. FIG. 7 is a graph of
the output of the shelving filter of FIG. 6 for early reflection in accordance with an example
implementation of the invention. FIG. 8 is a flow diagram of steps for virtual surround rendering
according to an example implementation of the present invention.
[0012]
Detailed Description It is to be understood that the following description of an exemplary
implementation is given for the purpose of illustration only and should not be taken in a limiting
sense. The division of examples of functional blocks, modules or units shown in the drawings
should not be construed as indicating that the functional blocks, modules or units are necessarily
implemented as physically separate units. The functional blocks, modules or units shown or
described may be implemented as separate units, circuits, chips, functions, modules or circuit
elements. One or more functional blocks or units may also be implemented in a common circuit,
chip, circuit element or unit.
[0013]
In FIG. 1, a diagram 100 of a speaker array or sound bar 102 is depicted in accordance with an
example of an implementation of the invention. The speaker array 102 may have more than one
speaker, such as speakers and associated transducers 104, 106, 108 and 110. The transducers
may be two small internal transducers 106 and 108 and two large external transducers 104 and
110. The speaker array 102 is generally placed in front of the listener. An example of mounting a
speaker array is above or below a flat screen television.
[0014]
Referring to FIG. 2, a simplified block diagram 200 of a digital signal processor (DSP) 202 in
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accordance with an example of an implementation of the invention is shown. The digital signal
processor is coupled to one or more memories such as memory 206, an analog-to-digital (A / D)
converter such as 208, clock 210, discrete component 212, digital-to-analog (D / A) converter
214 Can have a controller 204. One or more analog signals may be received by A / D converter
208 and converted to digital signals to be processed by controller 204, memory 206 and discrete
component 212. The processed signal may be output through D / A converter 214 and further
amplified or passed to other devices such as sound bar 102.
[0015]
Referring to FIG. 3, a block diagram 300 of a virtual surround sound processor (VSSP) 202
having a four channel surround renderer 302 implemented in the DSP 202 of FIG. 2 coupled to
the loudspeaker array 102 of FIG. Depicted. The VSSP 202 may have connectors that accept left
channel L 302, center channel C 304, and right channel R 306 audio. The audio from center
channel C 304 is coupled to left channel L 302 by combiner 308 and to right channel R 306 by
combiner 310. The outputs from the combiners 308 and 310 are passed to a 2 in 4 out up mixer
312. The outputs of the 2-in-4 out-up mixer 312 are four output signals (Out_L 314, Out_R 316,
Surr_out_L 318 and Surr_Out_R 320). The Surr_out_L signal 318 is coupled to the left signal
322 by the combiner 324 and the Surr_out_R signal 320 is coupled to the right signal 326 by
the combiner 328. The outputs from combiners 324 and 328 are passed to surround renderer
302. The output sends signals from surround renderer 302, A_L 330, A_R 332, B_L 334 and B_R
336. A_L signal 330 may be coupled to Out_L signal 314 by combiner 338 and coupled to
speaker 104 in sound bar 102. The Out_R signal 316 may be coupled to the A_R signal 332 by
the combiner 340 and coupled to the speaker 110 in the sound bar 102. The B_L signal 334 and
the B_R signal 336 are coupled to the speakers 106 and 108 in the sound bar 102, respectively.
[0016]
The center channel C304 is added to the left input channel L302 and the right input channel
R306, respectively, via the attenuation factor h1. In general, h1 may be set as h1 = 0.4, which in
the present example is about -8 dB. The summed signals are connected to the inputs IN_L and
IN_R (outputs of the combiners 308 and 310) of a 2-in-4 out-up mixer 312 (generating the main
stereo output Out_L 314, Out_R 316 and surround output Surr_Out_L 318, Surr_Out_R 320).
The main output is added directly to the signal feeding the external converter pair 104 and 110
via the two summing nodes or combiners 338 and 340. The surround output of the 2 in 4 out up
mixer 312 is integrated by the factor h3 respectively and added by the combiners 324 and 328
to the surround input channels LS 322 and RS 326 (integrated by the scaling factor h2). The
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resulting summed input signal is coupled to the first pair A_L 330 and A_R 332 and the internal
transducer pair 106 and 108 connected via the summing node (combiners 338 and 340) to the
four signals (external transducer pair 104 and 110). Connected to the input of the surround
renderer 302 which generates a second pair B_L 334 and B_R 336) connected thereto.
[0017]
Typical values for the scaling factor employed in the 2 in 4 out mixer 312 may be h2 = 2.3, h3 =
1.9, but other values are dependent on the application and user preferences and other
implementations Can be used in In the case of computer monitor applications, the external
transducers 104 and 110 may be spaced (40-50) cm apart, and the internal pairs 106 and 108
may be spaced apart (6-10 cm). This corresponds to an angular span to the listener's head +/−
(14-17) ° with respect to the outer pairs 104 and 110 at a listening distance of 80 cm and + /
−− for the inner pairs 106 and 108. Corresponds to (2-4) °. In home theater system
implementations where the external transducers 104 and 110 are spaced at the edge of a large
TV screen, for example, approximately 150 cm and the internal transducers 106 and 108 are
spaced 30 cm, at a listening distance of 250-300 cm. It will be similar angular span. The design
parameters depend primarily on the angular span and so may be the same for both of the
exemplary applications.
[0018]
Referring to FIG. 4, a block diagram 400 of the surround renderer 302 of FIG. 3 is depicted in
accordance with an example of an implementation of the invention. The two-channel (from
combiner 324) input signal Surr_In_L, (from combiner 328) Surr_In_R, first the spectrum is
divided into two signals by the crossover network at a specific crossover frequency fc410, the
low pass filters LP 402 and 404 Pair, includes a pair of high pass filters HP 406 and 408. The
crossover frequency fc is chosen such that a simple head model is valid (generally fc = 500 Hz to
2000 Hz). The crossover filter may be a low order recursive filter (eg, a second order Butterworth
(BW) filter or a fourth order Linkwitz-Riley (LR) filter). The lower section is further scaled down
by the factor g1412.
[0019]
The low-pass filtered signal pair then passes through the non-recursive (first-order) crosstalk
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canceller section through the cross path formed by the delay sections HD 414 and 416. Delay
sections HD 414 and 416, respectively, represent a pure delay of d1 samples, followed by a gain
g2418. The cross pass output is subtracted from the direct pass by combiners 420 and 422,
respectively, thereby canceling the signal arriving from the right transducer to the left ear and
from the left transducer to the right ear. At low frequencies below 700 Hz, the interaural time
difference (ITD) is a prominent focal stimulus and in the frequency range above 700 Hz, the
interaural level difference (ILD) becomes more dominant. At a particular listening angle, the path
difference in the crosstalk path corresponds to a delay value of d1 = (4... 8) samples at a
sampling rate of 48 kHz.
[0020]
The high-pass filtered signal pair is processed by the second crosstalk canceller with first-order
low-pass filters HC 424 and 426 in the cross path, the cross path being only characterized by the
-3 dB cut-off frequency ft428. The experimentally determined values for HC 424 and 426 are ft =
(3 ... 4) kHz in the current implementation. No additional delay or gain parameters are required
in this section. The output of HC 424 is subtracted from the output of HP 408 by combiner 430
resulting in an output signal B_R. Similarly, the output of HC 426 is subtracted from the output
of HP 406 by combiner 428 resulting in an output signal B_L.
[0021]
With the described two-way approach, first order head related models resembling ITD and ILD
localized stimulation in each frequency band have been used. Thereby, the higher order head
related filters taught in the prior art are avoided, resulting in less off-axis tone, phase and less
unpleasant sensation of ear pressure.
[0022]
A useful range for the cross path gain factor is generally g2 = (0.3... 0.9). However, a value close
to one result in maximum separation (virtual image along the axis across the listener's ear)
requires a maximum bass boost, the amount of which can be set by the choice of gain factor g1.
A typical design example for a computer monitor system is: LP, HP = second-order BW section, fc
= 800 Hz g1 = −3.0, HD = frequency response of delay d1 = 4 samples, g2 = 0.7, HC = first order
Low frequency, ft = 3.5 kHz.
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[0023]
The frequency response at the center position is g1.LP. (1-g2.HD) + HP. (1-HC) depending on the
mono input.
[0024]
At the off-axis position, a further path length difference HD1 between the left external converter
and the right external converter is given by the frequency response g1.LP. (1-g2.HD). (1 + HD1) /
2 + HP. (1-) Lead to HC).
[0025]
In FIG. 5, a graph 500 of the center position of the 5-channel surround renderer 302 of FIG. 3
and the summed response at 12 degrees off-axis is shown in accordance with an example of an
implementation of the invention.
At the assumed 12 ° off-axis angle (which results in the path length difference HD1 = 13 sample
delay between left and right external transducers) we are significantly flatter and further The
results shown in the graph 500 with the on-axis response 502 not requiring equalization while
the off-axis response 504 only shows interference dips around 1.5 kHz were obtained.
The interference dip is not strongly perceived as tonality and is further masked by the main
stereo signals L302, R306 and C304.
[0026]
Referring to FIG. 6, a block diagram 600 of the 2-in-4 out-up mixer 312 of FIG. 3 is depicted in
accordance with an example of an implementation of the invention. The purpose of the 2-in-4
out-up mixer 312 is to provide an extended stereo width and adjustable perceived distance of the
frontal sound stage, and a 2-channel only signal source (traditional signal source) To create an
enhanced spatial experience for the case.
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[0027]
Stereo width adjustment is achieved in the stereo width adjustment section 601 by two linear 2
× 2 matrices with main stereo pair Out_L 314, Out_R 316 negative cross coefficient b 1602 and
virtual surround pair Surr_Out_L 318, b2 604 for Surr_Out R 320 respectively. obtain. A useful
range of parameters is the interval [0. . . 1]. The values chosen for the current exemplary
implementation are b1 = 0.04, b2 = 0.33.
[0028]
The perceived distance of the sound stage can be increased beyond the speaker base by the
addition of the individual reflected energy in the distance adjustment section 605. As the
amplitude of the reflections increases and the reflections approach direct sound (smaller delay
values), the distance the sound can be perceived increases. In the present exemplary
implementation, four reflections (delayed replicas of direct sound) are made and added to the
four outputs of the 2 in 4 out up mixer 312. The parameters are four delay values (d1606,
d2608, d3610 and d4612) and their respective amplitudes (c1614, c2616, c3618 and c4620).
Sufficient decorrelation between the reflected signals can be achieved by assigning random
values, thereby avoiding fontomic imaging (merging two or more reflections into one) and
excessive tone. Exemplary parameter settings for the current implementation correspond to c1 =
0.62, c2 = 0.50, c3 = 0.71, c4 = 0.5 (-4 dB, -6 dB, -3 dB and -5 dB respectively) And d1 = 564, d2
= 496, d3 = 776, d4917 samples.
[0029]
In addition, a pair of primary high shelving filters 622 and 624 can be inserted into the reflective
path to stimulate natural wall absorption and attenuate non-periodic temporal signals in the
stimulated ambient sound field. General parameters for high shelving filters 622 and 624 are
depicted in FIG. In FIG. 7, a graph 700 of the output 702 of the shelving filters 622 and 624 of
FIG. 6 for early reflection in accordance with an exemplary implementation of the invention is
shown.
[0030]
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Referring to FIG. 8, a flowchart 800 of steps for virtual sound rendering according to an example
implementation of the invention is shown. Multiple audio signals, such as IN_L and IN_R, are
received at a 2 in 4 out up mixer 312 (802). The 2-in-4 out-up mixer 312 responds to the
reception of the first plurality of audio channel signals (804) with up-mixed output signals such
as Out_L 314 and Out_R 316 and associated output surround signals such as Surr_out_L 318
and Surr_out_R 320. Generate. A second plurality of audio channel signals, such as LS 322 and
RS 326, are received at surround renderer 302 (806). Each of the second plurality of audio
channel signals is coupled to an associated output surround signal in response to the second
plurality of audio channel signals being received by the combiner 324 and 328 (808) in the
surround renderer 302 . A plurality of transducer signals are generated as an output of surround
renderer 302, such as B_L 334 and B_R 336. Some of the plurality of transducer signals are
combined by the combiner to the associated up mixed output signal, such as A_L330 and
A_R332 coupled to Out_L 314 by combiners 338 and 340 (810). Generate additional transducer
signals.
[0031]
The method described with respect to FIG. 8 may include additional steps or modules that are
typically performed during signal processing to move data in memory and generate timing
signals. The depicted steps of the FIG. 8 may also be performed by or in parallel with further
steps or functions.
[0032]
It will be understood and appreciated by those skilled in the art that one or more processes, subprocesses or process steps or modules described in connection with FIG. 8 may be performed by
hardware and / or software. If the processing is performed by software, the software may be
software in a suitable electronic processing component or system, such as one or more of the
functional components or modules schematically depicted or identified in FIGS. May reside in
memory (not shown). Software in software memory may include an ordered listing of executable
instructions that implement logic functions (ie, “logic” that may also be implemented as digital
circuits or digital forms such as source code), and an instruction execution system, Apparatus or
computer-based system, system including a processor or instruction execution system, device or
a use such as a device such as any other system capable of selectively fetching instructions from
a device or use connected to them And may be selectively embodied on any computer readable
medium. In the context of the present disclosure, a "computer readable medium" may either
include, store or communicate a program for use connected to or by an instruction execution
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system, apparatus or device Tangible means of A computer readable medium may be, for
example, but is not limited to, selectively electronic, magnetic, optical, electromagnetic, infrared
or semiconductor systems, devices or devices. A more specific example, but still not exhaustive
list of computer readable media includes: portable computer diskette (magnetic), RAM
(electronic), read only memory "ROM" (ROM) Electronic), erasable programmable read only
memory "EPROM or flash memory" (electronic) and portable compact disc read only memory "CD
ROM" (optical). The computer readable medium may be paper or another suitable medium in
which the program is printed, captured and then compiled, interpreted or processed in an
appropriate manner as needed and then stored in computer memory Please note that.
[0033]
The foregoing description of implementations has been presented for purposes of illustration and
description only. The description is not exhaustive and does not limit the invention exactly from
the disclosure. Modifications and variations are possible in light of the above description or may
be acquired from practice of an example of the invention. The claims and their equivalents define
the scope of the invention.
[0034]
102 speaker array or sound bar 202 digital signal processor (DSP) 206 memory 208 analog to
digital (A / D) converter 210 clock 214 digital to analog (D / A) converter
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