JP2000069598A - Multi-channel surround reproducing device and reverberation sound generating method for multi- channel surround reproduction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the non-correlation of a reverberation sound, and to obtain a natural sound feeling without increasing a hardware scale by providing multi- level connected whole band pass filters in a final stage connected in parallel for the necessary number of channels for each necessary channel, and setting each feedback delay as an individual value for each channel. SOLUTION: A reverberation sound generating part is constituted of comb- shaped filters 21-24 for four channels, an adder 25 for adding the outputs of those comb-shaped filters 21-24, and two whole band pass filters 26 and 27. A non-correlation processing part is provided with whole band pass filters 31-34 in a final stage multi-level connected in parallel for each necessary channel, and each feedback delay is individually set for each channel so that the output of the reverberation sound generating part can be non-correlated and outputted. Thus, correlation among channels can be reduced by a simpler circuit than a reverberation sound generating circuit individually prepared for all channels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a multi-channel surround reproduction apparatus using sound image localization and a method for generating reverberation sound in multi-channel surround reproduction.

[0002]

2. Description of the Related Art In a multi-channel surround reproduction in which one surround sound is monaural, when a sound field of a hall or a movie theater is generated and added, sound effects of the sound field include left channel, center channel, right channel, and surround channel. Created using

[0003] The sound effect in the sound field generally consists of an early reflection sound and a rear reverberation sound. The sound effects are generated for four channels and mixed into the left channel, the right channel, and the surround channel, respectively. It creates sound space such as movie theaters.

FIG. 6 is a block diagram showing a basic multi-channel surround playback device. That is, the multi-channel surround playback device shown in FIG. 1 includes two channels of stereo signals L and R, a surround signal (rear channel signal) S for obtaining a surround sound effect, a center channel, and a center channel. Signal C and low frequency signal below 100 Hz (not shown)
And a left from the decoder unit 1,
The right channel and the front channels L, R, of the center channel.
An adder 2 as a forward channel adding means for adding C via a coefficient multiplier; and an initial reflected sound processing as a front channel initial reflected sound processing means for processing an initial reflected sound using an output from the adder 2 as an input signal. A unit 3 and an initial reflected sound processing unit 4 as a rear channel initial reflected sound processing unit that processes an initial reflected sound by using the rear channel S as an input signal.

Further, an adder 5 for adding the output from the adder 2 and the rear channel S via a coefficient multiplier, and a reverberation generator for generating a reverberation component using the output from the adder 5 as an input signal. 6, an adder 7 for adding the output signals of the early reflection sound processing units 3 and 4 of the front channel and the rear channel via a coefficient multiplier, and an output from the reverberation sound generation unit 6 and an output from the adder 7 Adder 8 that adds the following two channels through a coefficient multiplier, an adder 9 that adds two rear channels of the output from the adder 8 and the rear channel from the decoder unit 1 through a coefficient multiplier, Sound image localization processing unit 1 that performs sound image localization processing by using an output from adder 9 as an input
0, an output of the adder 8, two forward channels and an output from the sound image localization processing unit 10 are added through a coefficient multiplier, and an output signal from the adder 11 and the center channel C are left An adder 12 is provided to obtain the outputs of Lch and Rch by adding the channel L and the right channel R via a coefficient multiplier, respectively.

In the configuration shown in FIG. 6, the generation of reverberation in surround reproduction by the reverberation
Generally, as shown in FIG. 7 devised by Schrader, a comb filter (Comb Filter) and an all-pass filter (All-Pa
ss Filter) is used. That is, the reverberation generator 6 shown in FIG. 7 includes four channels of comb filters 21 to 24, an adder 25 that adds the outputs of the comb filters, all-pass filters 26 and 27, and all-pass filters. And an adder 28 for adding the input signal IN to the output of the output signal 27.

Here, each comb filter will be described by taking the comb filter 21 as an example.
A signal path through which an input signal passes is provided by inserting a loop constituted by a delay circuit having a delay time τ1, a feedback path having an amplifier having a gain g1 smaller than 1 and an adder. By successively attenuating the signal IN while repeatedly circulating, the reverberation signal of the input signal IN is selected on the output side. The comb filter 22
The delay time of the delay circuit and the gain of the amplifier are τ2 and g2,
The delay time of the delay circuit of the comb filter 23 and the gain of the amplifier are set to τ3 and g3, and the delay time of the delay circuit of the comb filter 24 and the gain of the amplifier are set to τ4 and g4.

As the all-pass filter, two all-pass filters 26 and 26 are used to increase the density of the reverberation signal in a natural sense and to obtain a practically sufficient diffusion of the reverberation sound.
27, the all-pass filter 26 will be described as an example. The all-pass filter 26 converts the reverberation sound through the adder 25 into a delay circuit with a delay time τ5, and an amplifier with a gain g5. Provided loop and gain-g
By circulating in a loop with five amplifiers, one creates more reverberation signals. Note that the delay time of the delay circuit of the all-pass filter 27 and the gain of the amplifier are τ
6, g6 and -g6.

[0009]

However, the circuit shown in FIG. 7 as the above-described reverberation sound generator 6 is basically a monaural circuit. Cannot be obtained. Therefore, it is necessary to decorrelate the reverberation component by some method.

The decorrelation is performed as follows: (1) A reverberation component is created independently for each channel. (2) Different delays are given to monaural reverberation components to shift the start times of reverberation sounds. And so on.

However, the above-mentioned method (1) requires a reverberation generation circuit independently for each channel, and therefore has the disadvantage of increasing the hardware scale. There was a problem that it was difficult to obtain a feeling and naturalness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a natural surround feeling without increasing the scale of hardware for achieving decorrelation of reverberation in multi-channel surround reproduction. It is an object of the present invention to provide a multi-channel surround playback device and a method for generating reverberation in multi-channel surround playback.

[0013]

In order to achieve the above object, a multi-channel surround reproducing apparatus according to the present invention provides a multi-channel surround reproducing apparatus in which a surround sound is a monaural one-channel multi-channel surround reproducing apparatus. A front channel adding means for adding channels, a front channel initial reflected sound processing means for processing an initial reflected sound using an output from the front channel adding means as an input signal, and a rear processing for an initial reflected sound using a rear channel as an input signal. Channel initial reflection sound processing means, first addition means for adding the output from the front channel addition means and the rear channel, and reverberation for generating a reverberation component using the output from the first addition means as an input signal. It is necessary to decorrelate the output signal of the sound generation means and the reverberation sound generation means. Decorrelating means for generating reverberation components for the number of channels, second adding means for adding an output signal from the front channel initial reflected sound processing means and an output signal from the rear channel initial reflected sound processing means, Third adding means for adding the output signal from the decorrelating means and the output signal from the second adding means, and the rear two channels and the rear channel of the outputs from the third adding means A fourth adding means for adding each; a sound image localization processing means for performing a sound image localization process by using an output from the fourth adding means as an input; two forward channels and the sound image among the outputs of the third adding means; Fifth adding means for adding the output from the localization processing means, and adding the output signal from the fifth adding means and the center channel to the left channel and the right channel, respectively. It is characterized in that a sixth addition means.

Further, in the multi-channel surround playback apparatus according to another invention, the multi-channel surround playback in which the surround sound has two independent channels is performed.
A front channel adding means for adding the front channels of the center channel, a front channel initial reflected sound processing means for processing an initial reflected sound by using an output from the front channel adding means as an input signal, and a rear for adding left and right rear channels. A channel addition unit, a rear channel initial reflection sound processing unit that processes an initial reflection sound by using an output from the rear channel addition unit as an input signal, an output from the front channel addition unit, and an output from the rear channel addition unit. First adding means for adding
A reverberation generator for generating a reverberation component using the output from the first addition unit as an input signal; and a demodulator for de-correlating the output signal of the reverberation generator to generate reverberation components for a required number of channels. Correlating means, second adding means for adding an output signal from the front channel initial reflected sound processing means and an output signal from the rear channel initial reflected sound processing means, and an output signal from the decorrelating means. The second
A third adding means for adding the output signals from the adding means, and a left and right two for the front and the rear from the third adding means.
Seventh adding means for adding the channels to the corresponding channels of the left channel, the right channel, the left surround channel and the right surround channel, respectively.

A multi-channel surround playback apparatus according to still another aspect of the present invention provides a multi-channel surround playback apparatus in which surround sound has two independent channels.
Front channel adding means for adding the front channels of the left, right and center channels; front channel initial reflected sound processing means for processing the initial reflected sound using the output from the front channel adding means as an input signal; and left and right rear channels Rear channel adding means for adding an output from the rear channel adding means, an output from the front channel adding means, and the rear channel adding means. Adding means for adding the output of the reverberant sound generating means for generating a reverberant sound component using the output from the first adding means as an input signal; Decorrelating means for generating reverberation components for the required number of channels, and said front channel initial reflected sound Second adding means for adding the output signal from the processing means and the output signal from the rear channel initial reflection sound processing means, and the output signal from the decorrelation means and the output signal from the second adding means. A third adding means for adding, and a fourth adding means for adding two rear left and right channels of the output from the third adding means to corresponding channels of a left surround channel and a right surround channel, respectively. A sound image localization processing means for performing a sound image localization process by using an output from the fourth addition means as an input, and two front left and right channels of the output from the third addition means, Fifth adding means for adding to the output, and eighth adding means for adding the output from the fifth adding means and the center channel to the left channel and the right channel, respectively. The is characterized in that it comprises.

In each of the above-described multi-channel surround sound reproducing apparatuses, the reverberation sound generating means includes a comb filter connected in parallel for a required number of channels and each feedback delay being individually set; And a multi-stage connected all-pass filter configured to increase the generation density of reverberation signals synthesized and output from the shape filter, wherein the decorrelation means requires a multi-stage connected all-pass filter at the final stage. Each feedback delay is set to an individual value for each channel, and the output from the reverberation generating means is decorrelated and output.

Further, in the method for generating reverberation sound in multi-channel surround reproduction according to the present invention, the reverberation sound generating step of generating a reverberation sound of an input signal for the required number of channels and outputting a synthesized signal; A decorrelation step in which all-pass filter processing in which each feedback delay is individually set for the required number of channels is performed in parallel on the signal passed through the generation step and the decorrelation sound of each channel is decorrelated. It is characterized by having.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> FIG.
1 is a configuration diagram illustrating a multi-channel surround playback device according to an embodiment of the present invention. 1, the same parts as those of the conventional multi-channel surround sound reproducing apparatus shown in FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted. As a new code, 13 constitutes a reverberation sound generation block together with the reverberation sound generation unit 6, and performs decorrelation of the output signal from the reverberation sound generation unit 6 to generate reverberation components for the required number of channels. The output of the decorrelation processor 13 is input to the adder 8 via a coefficient multiplier, and is added to the output of the adder 7 via the coefficient multiplier.

Here, the reverberation sound generation block composed of the reverberation sound generation section 6 and the decorrelation processing section 13 has the configuration shown in FIG. That is, similarly to the conventional example shown in FIG. 7, the comb filters 21 to 24 for four channels (the characteristic of the vector ω is expressed by the equation H (ω) = exp (−jωτi) / (1-gi · e).
xp (−jωτi)) where i = 1 to 4, gi is a gain, and τi is a delay time. ), An adder 25 that adds the outputs of the comb filters, and two all-pass filters 26 and 27 (the characteristic of the vector ω is expressed by the equation H (ω) = exp (−jωτi) · (1-gi · e
xp (jωτi) / (1-gi · exp (−jωτ)
i)) Here, i = 5, 6, and gi are gains, and τi is a delay time. Of the final stage all-pass filters 31 to 34 (the vectors of which are connected in multistage in parallel for each required channel) as the decorrelation processing unit 13 for the reverberation sound generation unit 6 configured by The characteristic of ω is expressed as follows: H (ω) = exp (−jωτi) · (1-gi · e)
xp (jωτi) / (1-gi · exp (−jωτ)
i)) where i = 7 to 10, gi is a gain, and τi is a delay time. Can be realized by)
Each feedback delay is individually set for each channel, and the output from the reverberation sound generator 6 is decorrelated and output.

For example, the all-pass filter 31 will be described. The all-pass filter 31 converts the reverberation sound passed through the all-pass filter 27 into a delay circuit having a delay time τ7, a loop having an amplifier having a gain g7, and a loop having a gain of -g7. All reverberation signals are created by circulating in a loop with an amplifier. Similarly, the all-pass filter 32 includes a delay circuit with a delay time τ8, a loop with an amplifier with a gain g8, and a gain −g8. The all-pass filter 33 includes a delay circuit having a delay time τ9, a loop including an amplifier having a gain g9, and a gain −g.
Loop with all nine amplifiers
Has a delay circuit having a delay time τ10, a loop having an amplifier having a gain of g10, and a loop having an amplifier having a gain of −g10. Each feedback delay of the comb filter is set, for example, to a value between 20 and 100 ms. Each feedback delay of the all-pass filter is set to a value between 2 and 40 ms, for example.

FIG. 3 is a flowchart showing processing steps for explaining a reverberation sound generating method in multi-channel surround reproduction. First, in the reverberation generation step S1, like the reverberation generation unit 6 shown in FIG.
A monaural input signal of one channel is generated for the required number of channels and the synthesized signal is output. Then, in the decorrelation processing step S2, as in the decorrelation processing unit 13 shown in FIG. 1, each feedback delay is set individually for the number of channels required for the signal passed through the reverberation sound generation step S1. All-pass filtering is performed in parallel to output the decorrelated reverberation sound of each channel.

As described above, by preparing the all-pass filter at the final stage for each channel and setting the value of each feedback delay to a different value for each channel, the correlation between channels can be reduced. A natural reverberation can be obtained. Further, similar effects can be obtained with a simpler circuit than in the case where individual reverberation generation circuits are prepared for all channels. By providing a surround playback program having processing steps as shown in FIG. 3, the correlation between channels can be reduced, and software processing can be performed to obtain a natural reverberation sound.

Therefore, according to the first embodiment,
Prepare the final stage all-pass filter for each channel,
By setting the value of each feedback delay to a different value for each channel, the correlation between channels can be reduced,
A natural surround feeling can be obtained without deteriorating the hardware scale for decorrelating reverberant sounds in multi-channel surround reproduction by sound image localization.

<Second Embodiment> In the first embodiment described above, multi-channel surround reproduction is performed by localizing a sound image of one monaural surround sound, but in the second embodiment, surround sound is reproduced. Multi-channel surround reproduction with two independent channels will be described.

FIG. 4 is a block diagram showing a multi-channel surround playback device according to the second embodiment. 4, the same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. As a new code,
1A is a two-channel stereo signal L, R from a signal in which a surround signal is encoded, two-channel surround signals (rear channel signals) S1, Sr for obtaining a surround sound effect, and a center channel signal C.
And a low frequency signal LFE of 100 Hz or less.

Reference numeral 14 denotes left and right rear channel signals S.
A rear channel adder for adding 1 and Sr. An output signal of the adder 14 is input to the initial reflected sound processing unit 4 and subjected to initial reflected sound processing, and is also input to the adder 5 via a coefficient multiplier. The output is added to the output of the adder 2 of the front channel via another coefficient multiplier, and the added output is input to the reverberation sound generation block. further,
Reference numeral 15 designates the left and right two-channel signals for the front and rear through the adder 8 to the corresponding channels of the left channel L, the right channel R, the left surround channel S1, and the right surround channel Sr from the decoder section 1A. These are adders that add and output each through a coefficient multiplier. 4 does not include the sound image localization processing unit 10 shown in FIG.

The reverberation sound generation block composed of the reverberation generation unit 6 and the decorrelation processing unit 13 in the second embodiment is, as shown in FIG. 2, similar to the first embodiment. In addition, a final stage all-pass filter is prepared for each channel, and the value of each feedback delay is set to a different value for each channel, so that the correlation between channels can be reduced and natural reverberation can be reduced. So you can get it. The value of each feedback delay is specifically set between several ms and several hundred ms.

Therefore, according to the second embodiment,
Even in the case of multi-channel surround reproduction in which the surround sound is two independent channels, as in the first embodiment, a final stage all-pass filter is prepared for each channel, and the value of each feedback delay is set for each channel. By using different values, the correlation between channels can be reduced, and there is no need for independent reverberation generation means for each channel to achieve decorrelation of reverberation in multi-channel surround playback. Therefore, a natural surround feeling can be obtained without increasing the scale of hardware and without discomfort.

<Third Embodiment> In the above-described first embodiment, multi-channel surround reproduction by sound image localization of one monaural surround sound will be described. In the above-described second embodiment, In the third embodiment, the multi-channel surround reproduction using the sound image localization of the independent two-channel surround sound will be described in the third embodiment.

FIG. 5 is a configuration diagram showing a multi-channel surround playback device according to the third embodiment. In FIG. 5, the same parts as those in the first and third embodiments shown in FIGS. 1 and 4 are denoted by the same reference numerals, and description thereof will be omitted. As a new code, 16 outputs two front left and right channels from the sound image localization processing unit 10 out of the output from the adder 8 obtained by adding the output signal from the decorrelation processing unit 13 and the output signal from the adder 7. The output from the adder 11 added to the output of the decoder unit 1, the center channel signal C from the decoder unit 1A, and the low-frequency signal LFE of 100 Hz or less are
This is an adder that adds the left and right channel signals L and R from A to each other and outputs the result. The value of each feedback delay is set between several ms and several hundred ms.

Further, the reverberation sound generation block constituted by the reverberation sound generation section 6 and the decorrelation processing section 13 in the third embodiment is similar to the first and second embodiments in FIG. As shown in (2), by preparing a final-stage all-pass filter for each channel and setting the value of each feedback delay to a different value for each channel, the correlation between channels can be reduced and natural The reverberation can be obtained.

Therefore, according to the third embodiment,
Even when the surround sound is multi-channel surround reproduction by sound image localization of two independent channels, the first and second surround sound are reproduced.
In the same manner as in the first embodiment, the all-pass filter in the final stage is prepared for each channel, and the value of each feedback delay is set to a different value for each channel, so that the correlation between channels can be reduced. It is possible to eliminate the need for independent reverberation generation means for each channel to achieve decorrelation of reverberation sound in multi-channel surround playback by sound image localization. A natural surround feeling can be obtained.

[0033]

As described above, according to the multi-channel surround reproduction apparatus and the reverberation sound generation method for multi-channel reproduction according to the present invention,
By performing the final stage all-pass filtering for each channel that requires it, and by setting individual feedback delay values to different values for each channel, the correlation between channels can be reduced and multi-channel surround playback Therefore, a natural surround feeling can be obtained without increasing the hardware scale for de-correlation of the reverberation sound.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a multi-channel surround playback device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a reverberation generation block according to the present invention.

FIG. 3 is a flowchart for explaining a reverberation sound generation method in multi-channel surround playback according to the present invention.

FIG. 4 is a configuration diagram illustrating a multi-channel surround playback device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a multi-channel surround playback device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram showing a conventional basic multi-channel surround playback device.

FIG. 7 is a configuration diagram showing a generation circuit combining a comb filter and an all-pass filter.

[Explanation of symbols]

1, 1A decoder unit 2 Adder (front channel adding means) 3 Early reflected sound processing unit (front channel initial reflected sound processing means) 4 Early reflected sound processing unit (rear channel initial reflected sound processing means) 5 Adder (first 6 reverberant sound generator (reverberant sound generator) 7 adder (second adder) 8 adder (third adder) 9 adder (fourth adder) 10 sound image localization processor (Sound image localization processing means) 11 Adder (fifth addition means) 12 Adder (sixth addition means) 13 Decorrelation processing section (Decorrelation means) 14 Adder (rear channel addition means) 15 Adder ( Seventh adding means) 16 adder (eighth adding means) 21 to 24 Comb filters 26, 27 All-pass filters 31 to 34 Multistage connected all-pass filters at the final stage constituting decorrelation means

Claims (5)

[Claims] 1. A multi-channel surround-sound reproducing apparatus in which surround sound is monaural in one channel, a front channel adding means for adding front channels of left, right, and center channels, and an output from the front channel adding means as an input signal. Front channel initial reflected sound processing means for processing the initial reflected sound; rear channel initial reflected sound processing means for processing the initial reflected sound by using the rear channel as an input signal; and adding the output from the front channel adding means and the rear channel. A reverberation generator for generating a reverberation component by using an output from the first addition as an input signal; a required number of channels obtained by decorrelating the output signal of the reverberation generator. De-correlation means for generating a reverberation component of the front channel; Second adding means for adding the output signal from the means and the output signal from the rear channel early reflection sound processing means, and adding the output signal from the decorrelation means and the output signal from the second adding means. A third adding unit that performs addition, a fourth adding unit that adds the rear two channels and the rear channel of the output from the third adding unit, and an output from the fourth adding unit as an input. Sound image localization processing means for performing sound image localization processing; fifth output means for adding the two front channels and the output from the sound image localization processing means among the outputs of the third addition means; and the fifth addition means. And a sixth adding means for adding the output signal from the first channel and the center channel to the left channel and the right channel, respectively. 2. A multi-channel surround-sound reproducing apparatus having two independent surround sounds, a front channel adding means for adding front channels of left, right and center channels, and an output from said front channel adding means as an input signal. Front channel initial reflection sound processing means for processing an initial reflection sound; rear channel addition means for adding left and right rear channels; and rear channel initial reflection for processing an initial reflection sound using an output from the rear channel addition means as an input signal. Sound processing means, first addition means for adding an output from the front channel addition means and an output from the rear channel addition means, and a reverberation component using the output from the first addition means as an input signal. Generating the reverberant sound generating means, Decorrelating means for generating reverberation components for the required number of channels by correlation, and a second means for adding an output signal from the front channel initial reflected sound processing means and an output signal from the rear channel initial reflected sound processing means. Adding means for adding an output signal from the decorrelating means and an output signal from the second adding means; forward and rear left and right from the third adding means 7. A multi-channel surround playback device comprising: a seventh addition unit that adds two channels to corresponding channels of a left channel, a right channel, a left surround channel, and a right surround channel, respectively. 3. A multi-channel surround sound reproducing apparatus having two independent independent surround sounds, a front channel adding means for adding front channels of left, right and center channels, and an output from said front channel adding means as an input signal. Front channel initial reflection sound processing means for processing an initial reflection sound; rear channel addition means for adding left and right rear channels; and rear channel initial reflection for processing an initial reflection sound using an output from the rear channel addition means as an input signal. Sound processing means, first addition means for adding an output from the front channel addition means and an output from the rear channel addition means, and a reverberation component using the output from the first addition means as an input signal. Generating the reverberant sound generating means, Decorrelating means for generating reverberation components for the required number of channels by correlation, and a second means for adding an output signal from the front channel initial reflected sound processing means and an output signal from the rear channel initial reflected sound processing means. Adding means for adding an output signal from the decorrelating means and an output signal from the second adding means; and a rear left and right output among the outputs from the third adding means. A fourth addition unit that adds two channels to the corresponding channels of the left surround channel and the right surround channel, and a sound image localization processing unit that performs a sound image localization process by using an output from the fourth addition unit as an input; A fifth adding unit that adds two front left and right channels of the output from the third adding unit to an output from the sound image localization processing unit; A multi-channel surround playback device, comprising: an eighth addition means for adding the output from the calculation means and the center channel to the left channel and the right channel, respectively. 4. The multi-channel surround reproducing apparatus according to claim 1, wherein said reverberation sound generating means are connected in parallel for a required number of channels, and each feedback delay is individually set. And a multistage connected all-pass filter configured to increase the generation density of reverberation signals synthesized and output from the comb filters. And providing the final stage all-pass filter for each of the channels that require it, setting each feedback delay to an individual value for each channel, and decorrelating the output from the reverberation sound generating means for output. Multi-channel surround playback device. 5. A reverberation sound generating method for multi-channel surround reproduction, comprising the steps of: generating a reverberation sound of an input signal for a required number of channels and outputting a synthesized signal; A de-correlation step of executing, in parallel, all-pass filter processing in which respective feedback delays are individually set for the required number of channels for the required signals, and outputting decorrelated reverberation sounds of the respective channels. A method of generating reverberation in multi-channel surround playback, comprising: