JP2017192024A - Channel number converter, broadcasting receiver and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To match an average loudness value of the entire programs with a target loudness value while keeping the signal level of a main channel before conversion constant in performing channel number conversion of program sound.SOLUTION: A channel number converter 10 relating to this invention includes: channel distribution means 11 for distributing all channels constituting program sound into between a main channel and normal channels; signal level correction value calculation means 12 for performing respective channel number conversion of the main channel and the entire channels, and calculating a signal level correction value of the normal channels so as to make a difference between a difference between the target loudness value and an average loudness value La of the main channel after the channel number conversion and a difference between an average loudness value Lb of the entire channels after the channel number conversion and the average loudness value La be within a prescribed range; and channel number conversion means 13 for correcting the signal level of the normal channels with the calculated signal level correction value to perform channel number conversion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a channel number conversion device, a broadcast receiver, and a program for converting the channel number of program audio.

  Conventionally, program audio level management has been performed using a VU meter (Volume Unit meter) or the like so that the instantaneous value of the audio signal does not overshoot. In recent years, operational regulations have been established so that the average loudness value over the entire program calculated by the loudness measurement method defined in Non-Patent Document 1 falls within the allowable range (± 1 dB) of the target loudness value (−24LKFS). (See Non-Patent Document 2).

  On the other hand, when program audio produced with multiple channels is played back with a smaller number of channels than at the time of production, the number of channels can be converted (down) by multiplying the audio signal of some channels by the downmix coefficient and adding each channel. Mixing) is performed (see Non-Patent Document 3).

Recommendation ITU-R BS.1770-4; "Algorithms to measure audio program loudness and true-peak audio level" ARIB TR-B32; "Loudness Operation Rules for Digital TV Broadcasting Programs" ARIB STD-B32; "Video coding, audio coding and multiplexing systems in digital broadcasting"

  In the loudness measurement method defined in Non-Patent Document 1, the average loudness value is calculated by multiplying the audio signal of each channel by a coefficient based on the position of the speaker reproducing each channel. Here, when the audio signal of the channel played from the side or the rear is played from a position such as the front that is different from the production by the channel number conversion, the coefficient multiplied by each channel is different, so the number of channels is converted. The average loudness value may change before and after. If the average loudness value of the entire program is adjusted to the target loudness value after converting the number of channels, the signal level of the main channel that was originally in front will also increase or decrease, and the impression of the entire program will change greatly by converting the number of channels. Sometimes. Also, if the average loudness value is adjusted to the target loudness value by increasing / decreasing only the signal level of some channels after converting the number of channels, the signal level balance between channels will be disturbed, and sound will be heard from the direction intended by the producer. Problems such as inability to hear occur.

  The object of the present invention is to solve the above-described problems and to convert the average loudness value of the entire program to the target loudness value while maintaining the signal level of the main channels before conversion constant when converting the number of channels of program audio. An object of the present invention is to provide a channel number conversion device, a broadcast receiver, and a program that can be matched.

  In order to solve the above-mentioned problem, a channel number conversion device according to the present invention is a channel number conversion device for converting the channel number of program audio, wherein all the channels constituting the program audio do not adjust the signal level. And a channel distribution means for distributing the signal level to a normal channel, and a first average which is an average loudness value of the main channel after the conversion of the number of channels. A second average loudness value, which is a loudness value and an average loudness value of all channels after the conversion of the number of channels, is calculated, a difference between a target loudness value and the first average loudness value, and the second average loudness value And the difference between the first average loudness value is within a predetermined range. A signal level correction value calculation means for calculating a signal level correction value for the normal channel; and a signal level correction value calculated by the signal level correction value calculation means for correcting the signal level of the normal channel; Channel number conversion means for performing channel number conversion using the normal channel after the signal level correction.

  In order to solve the above-described problem, in the channel number conversion device according to the present invention, the signal level correction value calculation means is configured such that audio signals of channels allocated to a plurality of channels by channel number conversion are transmitted to the plurality of channels. It is preferable to allocate the same ratio before and after the adjustment of the signal level.

  In order to solve the above-mentioned problem, in the channel number conversion device according to the present invention, the signal level correction value calculation means performs channel number conversion using a normal channel whose signal level is corrected by the calculated signal level correction value. When the difference between the target loudness value and the second average loudness value is not less than a threshold value, the signal level correction value is calculated using the main channel and the normal channel after the signal level correction. It is preferable to repeat the calculation.

  In order to solve the above problem, a broadcast receiver according to the present invention is a broadcast receiver including any one of the above-described channel number conversion devices, and the signal level correction value calculating means The average loudness value before the conversion of the number of channels from the beginning to the predetermined time is recorded, the difference between the recorded average loudness value before the conversion of the number of channels and the first average loudness value, and the second average loudness value The signal level correction value at the predetermined time is calculated so that the difference from the difference from the first average loudness value is within a predetermined range.

  Moreover, in order to solve the said subject, the program which concerns on this invention makes a computer function as said channel number conversion apparatus.

  According to the channel number conversion device, the broadcast receiver, and the program according to the present invention, when converting the number of channels of program audio, the average loudness value of the entire program is maintained while keeping the signal level of the main channel before conversion constant. Can be matched to the target loudness value.

It is a block diagram which shows the structural example of the channel number converter which concerns on one Embodiment of this invention. It is a figure which shows an example of a channel number conversion coefficient. It is a figure which shows an example of the arrangement | positioning of the channel after channel number conversion, and the weighting coefficient according to direction of each channel. It is a figure which shows an example of the arrangement | positioning of the channel before channel number conversion, and the weighting coefficient according to direction of each channel. It is a figure which shows the difference in the weight coefficient according to direction before and after channel number conversion. It is a figure which shows typically the measuring method of an average loudness value. It is a figure which shows the change of the signal level of the channel before and behind channel number conversion. It is a figure which shows an example of the channel number conversion coefficient which the channel number conversion means shown in FIG. 1 uses. 3 is a flowchart illustrating an example of an operation of a signal level correction value calculation unit illustrated in FIG. 1.

  Embodiments of the present invention will be described below.

  FIG. 1 is a block diagram illustrating a configuration example of a channel number conversion apparatus 10 according to an embodiment of the present invention. The channel number conversion apparatus 10 according to the present embodiment is incorporated in a production apparatus that produces a program, or a receiving apparatus (broadcast receiver) such as a television that receives and reproduces program audio, and produces the number N of channels. Channel number conversion is performed to convert the program audio into a signal with a channel number M different from that at the time of production.

  The channel number conversion apparatus 10 shown in FIG. 1 includes channel distribution means 11, signal level correction value calculation means 12, and channel number conversion means 13.

  The channel distribution means 11 receives an audio signal (input signal) before conversion of the channel number, which is a program audio produced with the number of channels N, and a channel identification signal for identifying the main channel. Here, the main channel is a channel (channel group) in which the signal level is not adjusted before and after the channel number conversion among the channels constituting the program audio. For example, a channel on which main information is recorded, such as a center channel (channel C), a left channel (channel L), and a right channel (channel R), is assigned to the main channel. For example, when a program is played, a channel played by a speaker arranged around a display device that displays the program is assigned to the main channel.

  The channel distribution means 11 extracts the channel indicated by the main channel identification signal from the channels constituting the input signal as the main channel. Then, the channel distribution unit 11 outputs the N number of input signals (audio signals before channel number conversion) and the extracted main channels (main channel group) to the signal level correction value calculation unit 12.

  The signal level correction value calculation means 12 receives the audio signal before channel number conversion and the main channel group from the channel distribution means 11. Further, the signal level correction value calculation means 12 includes a channel number conversion coefficient (N × M) used for channel number conversion, each channel before channel number conversion (N), and each channel after channel number conversion (M). ) Is input, the speaker position information which is the position information of the speaker to be reproduced.

  The signal level correction value calculation means 12 uses the audio signal before the channel number conversion, the main channel group, the channel number conversion coefficient, and the speaker position information, among the channels before the channel number conversion, that is, the channels other than the main channel, Then, a signal level correction value of a channel (hereinafter referred to as a normal channel) whose signal level is adjusted before and after the channel number conversion is calculated. Then, the signal level correction value calculation unit 12 outputs the calculated signal level correction value to the channel number conversion unit 13. Details of the signal level correction value calculation method will be described later.

  The channel number conversion means 13 receives an input signal of N channels, a main channel identification signal, and a channel number conversion coefficient. Further, the signal level correction value is input from the signal level correction value calculation unit 12 to the channel number conversion unit 13.

  The channel number conversion means 13 extracts channels other than the main channel indicated by the main channel identification signal from the channels constituting the input signal as normal channels, and multiplies the extracted normal channel audio signal by a signal level correction value. Then, the signal level of the normal channel is corrected. Then, the channel number conversion means 13 performs channel number conversion by multiplying the main channel and the normal channel whose signal level is corrected by a channel number conversion coefficient, and converts the channel number converted audio signal (M channel audio signal). Output as an output signal.

  In FIG. 1, the main channel identification signal, the speaker position information, and the channel number conversion coefficient have been described using an example that is input from the outside of the channel number conversion device 10, but the present invention is not limited to this. When the number of channels before and after channel number conversion, the position of the speaker that reproduces the audio signal of each channel, etc. are known, the speaker position information and the channel number conversion coefficient are stored in advance in the channel number conversion device 10. It may be left. In addition, when the position of the speaker for reproducing the audio signal of each channel is known, it is possible to determine in advance which channel should be set as the main channel, so that a specific channel is set as the main channel in advance. The channel number conversion device 10 may store a main channel identification signal indicating the main channel.

  Next, a method for calculating the signal level correction value will be described.

  First, the outline of the method for calculating the signal level correction value will be described. The signal level correction value calculation means 12 performs channel number conversion for each of the main channel and all the channels constituting the input signal using the channel number conversion coefficient. Next, the signal level correction value calculation means 12 calculates the average loudness value (first average loudness value) of the main channel after the channel number conversion and the average loudness value (second average loudness value) of all the channels after the channel number conversion. ) Is calculated. Then, the signal level correction value calculation means 12 determines that the difference between the target loudness value and the average loudness value of the main channel after the channel number conversion is the difference between the average loudness value of all the channels after the channel number conversion and the main channel after the channel number conversion. The signal level correction value of the normal channel is calculated so as to coincide with the difference from the average loudness value.

  Hereinafter, a method for calculating the signal level correction value will be described in more detail.

  An example of the channel number conversion coefficient used for the channel number conversion is shown in FIG. The channel 21 before channel number conversion is defined as seven channels C, L, R, SL, SR, BL, BR, and the channel 22 after channel number conversion is defined as five channels C ′, L ′, R ′, Ls ′, Rs. Then, the channel 22 after channel number conversion is calculated by multiplying the channel 21 before channel number conversion by the 5 × 7 channel number conversion coefficient 23 shown in FIG. In the example shown in FIG. 2, the side channels SL and SR are allocated to the front channels L ′ and R ′ and the rear channels Ls ′ and Rs ′.

  The signal level correction value calculation means 12 performs channel number conversion for each of the main channels and all the channels constituting the input signal based on the formula shown in FIG. Next, the signal level correction value calculation means 12 calculates the average loudness value of the main channel after the channel number conversion and the average loudness value of all the channels after the channel number conversion.

  Here, Non-Patent Document 1 stipulates that each channel is multiplied by a weighting factor (direction-wise weighting factor) so that the contribution to the average loudness value differs depending on the channel direction.

FIG. 3A is a diagram showing the arrangement of channels after conversion of the number of channels and the direction-specific weighting coefficient of each channel. Non-Patent Document 1 stipulates that the rear channels Ls and Rs contribute more to the average loudness value than the front channels. For example, as shown in FIG. 3A, the weight coefficient G _Rs of the rear channel Rs is 1.414, whereas the weight coefficient G _c of the front channel C and the weight coefficient GR of the channel _R are 1.0. is there.

FIG. 3B is a diagram showing the channel arrangement before the channel number conversion and the direction-specific weighting coefficient of each channel. Non-Patent Document 1 stipulates that the side channels SL and SR have a larger contribution to the average loudness value than the front and rear channels. For example, as shown in FIG 3B, while the weighting factor G _SR channel SR lateral is 1.414, the weighting factor G _c of the front channel C, the weighting factor G _R and the rear channels of the channel R The BR weighting coefficient G _BR is 1.0.

  FIG. 3C is a diagram illustrating a difference in weighting coefficient before and after channel number conversion.

  When the channel number conversion coefficient 23 shown in FIG. 2 is used, as shown in FIG. 3C, the channels SL and SR having a large weighting coefficient are allocated to the channels L ′ and R ′ having no large weighting coefficient, and the weighting coefficient is large. None of the channels BL and BR are allocated to the channels Ls ′ and Rs ′ having a large weight coefficient. Therefore, by performing the channel number conversion, the average loudness value changes even if the signal level does not increase or decrease.

  FIG. 4 is a diagram schematically showing a measurement method (calculation method) of the average loudness value.

  First, for each channel (5 channels in FIG. 4), an audio signal in a 400 ms section is cut out, and filter processing is performed on the cut out audio signal. Next, the root mean square of the audio signal of each channel after filtering is calculated. Next, the value of the mean square of the audio signal of each channel is multiplied by a weighting factor (direction-specific weighting factor) determined for each channel. Note that the weighting coefficient of each channel can be obtained from the speaker position information. Then, an addition process for adding the values of the respective channels multiplied by the weighting coefficient is performed, and an added value Zt is calculated.

At this time, the instantaneous loudness value at each time can be calculated based on the following equation (1).
Lt = −0.691 + ₁₀ log ₁₀ Zt (LKFS) (1)

  When Lt calculated based on the formula (1) is below an absolute threshold (−70 LKFS) or a relative threshold (a value smaller by 10 LKFS than the average value), it is considered as an invalid section that does not contribute to the sound volume of the entire program on hearing. After deletion, the average of the remaining sections (effective sections) is calculated as the average loudness value. In the program production, the signal level of each channel is adjusted so that the average loudness value becomes the target loudness value (−24LKFS).

  FIG. 5 is a diagram illustrating an example of the signal level of each channel before and after channel number conversion. FIG. 5 shows an example in which the 11-channel audio signal before the channel number conversion shown in FIG. 5A is converted into a 5-channel audio signal by the channel number conversion as shown in FIG. 5B. .

  In the example shown in FIG. 5, the channel C before the channel number conversion is allocated to the channel C ′ after the channel number conversion. The channel L before channel number conversion is assigned to the channel L ′ after channel number conversion. The channel R before the channel number conversion is allocated to the channel R ′ after the channel number conversion. The channel SL before the channel number conversion is equally divided and assigned to the channel L ′ and the channel Ls ′ after the channel number conversion. The channel SR before the channel number conversion is equally divided and assigned to the channel R ′ and the channel Rs ′ after the channel number conversion. The channel BL before the channel number conversion is allocated to the channel Ls ′ after the channel number conversion. The channel BR before the channel number conversion is allocated to the channel Rs ′ after the channel number conversion. The channel TpL before channel number conversion is assigned to the channel L ′ after channel number conversion. The channel TpR before channel number conversion is assigned to the channel R ′ after channel number conversion. The channel TpBL before the channel number conversion is allocated to the channel Ls ′ after the channel number conversion. Further, the channel TpBR before the channel number conversion is allocated to the channel Rs ′ after the channel number conversion. Here, the addition value (addition value Zt shown in FIG. 4) of the signal level of each channel before the channel number conversion is a value corresponding to −24LKFS.

  When the weight coefficient of the channels BL and BR before the channel number conversion is 1.0 and the weight coefficient of the channels Ls ′ and Rs ′ to which the channels BL and BR are allocated by the channel number conversion is 1.414 (channel number conversion When the later weighting factor is larger), the sum of the total signal levels after the channel number conversion is equal to the difference dif corresponding to the increase in the weighting factor of the total signal level before the channel number conversion. It is necessary to adjust the signal level of each channel so as to be smaller than the added value.

  Here, as a method of adjusting the overall signal level after the channel number conversion, a method of reducing the signal levels of all channels before the channel number conversion (FIG. 5C) is conceivable. However, with this method, the signal level of channels (for example, channels C, L, and R) in which main information is recorded is also reduced.

  Further, as a method of adjusting the overall signal level after the channel number conversion, the signal levels of the channels allocated to the channels C ′, L ′, and R ′ by the channel number conversion remain constant, and the side channels Ls ′ and Rs remain constant. A method of reducing the signal level of the channel assigned to '(Fig. 5 (d)) is conceivable. In FIG. 5, channels with diagonal diagonal lines rising to the right indicate that the signal level is constant before and after channel number conversion.

  In this method, the signal level of the channel SL changes between the channel Ls ′ and the channel L ′, which should originally be divided into the channels SL, and the channel Rs ′ and the channel R where the channel SR should be divided equally. 'Will change the signal level of channel SR. As a result, the audio signals of the channels SL and SR are heard from a direction different from the direction that is supposed to be heard.

  Therefore, in the present embodiment, as shown in FIG. 5E, the signal level correction value calculation means 12 has a fixed signal level of the main channel (for example, channels C, L, R) before the channel number conversion. The overall signal level is adjusted by reducing the signal level of the remaining channels (normal channels). That is, the signal level correction value calculation means 12 calculates a signal level correction value for adjusting the signal level of the normal channel so that the overall signal level after the number of channels conversion becomes the target value.

More specifically, the signal level correction value calculation means 12 adds the added value Za of the main channel after the channel number conversion, its average loudness value La (first average loudness value), and all the channels after the channel number conversion. The value Zb and its average loudness value Lb (second average loudness value) are calculated by performing the processing described with reference to FIG. Then, the signal level correction value calculation means 12 sets the signal level correction value C _T based on the following equation (2), where Lo is the target loudness value (for example, −24LKFS) and Zo is the corresponding added value. calculate.
C _T = ((Zo−Za) / (Zb−Za)) ^1/2 ... Formula (2)

That is, the signal level correction value calculation means 12 performs channel number conversion for each of the main channel and all channels using the input channel number conversion coefficient. Next, the signal level correction value calculation means 12 calculates the average loudness value La (first average loudness value) of the main channel after the channel number conversion and the average loudness value Lb (second second) of all the channels after the channel number conversion. Average loudness value). Then, the signal level correction value calculation means 12 determines that the difference between the target loudness value and the average loudness value La of the main channel after the channel number conversion is the difference between the average loudness value Lb of all the channels after the channel number conversion and the channel number conversion. to match the difference between the average loudness value La of the main channel, to calculate the signal level correction value C _T of the normal channel.

Note that, as described with reference to FIG. 4, the addition value of each channel of the audio signal every 400 ms is calculated, and the instantaneous loudness value is calculated from the addition value based on Expression (1). Then, an average loudness value is calculated from the instantaneous loudness value. Since the loudness value is logarithmic, it is necessary to use an added value in order to obtain an arithmetic average. The average Za of the addition values of the main channels after conversion of the number of channels corresponds to the average loudness value La, and the average Zb of the addition values of all the channels after conversion of the number of channels corresponds to the average loudness value Lb. Thus, in the formula (2), addition values Za, Zb, but calculates the signal level correction value C _T with Zo, which is the average loudness value La, with Lb and the target loudness value Lo signal it is equivalent to calculating the level correction value C _T.

In the present embodiment, an example in which the signal level correction value _CT is calculated so that the difference between the target loudness value and the average loudness value La matches the difference between the average loudness value Lb and the average loudness value La. However, the present invention is not limited to this. For example, the signal level correction value calculation means 12 outputs the signal so that the difference between the target loudness value and the average loudness value La and the difference between the average loudness value Lb and the average loudness value La are within a predetermined range. it may be calculated level correction value C _T.

Number conversion means 13 channel, as shown in FIG. 6, typically channel by multiplying (channel SL, SR, BL, BR) signal level correction value C _T to the audio signal, and corrects the signal level of the normal channel, The number of channels is converted by multiplying the main channel and the normal channel whose signal level is corrected by a channel number conversion coefficient. In this way, when converting the program audio into a channel number different from that at the time of production, the average loudness value of the entire program can be matched to the target loudness value while keeping the signal level of the main channel before conversion constant. it can.

Depending on the signal, the signal level may increase or decrease more than expected, such as when there is a correlation between channels, or when there is a section that exceeds the threshold (absolute threshold, relative threshold) due to increase or decrease of the signal level. There is a case where the average loudness value does not fall within a desired error range (a case where the difference between the target loudness value and the actual average loudness value does not become a predetermined value or less). In this case, the signal level correction value calculation means 12 performs the same calculation again using the first adjustment result as a new input signal, and the signal level correction value C _T until the average loudness value falls within the desired error range. Repeat the calculation.

  FIG. 7 is a flowchart showing the operation of the channel number conversion apparatus 10 according to the present embodiment.

  When the audio signal is input, the channel distribution unit 11 allocates the channels constituting the input audio signal based on the main channel identification signal (step S101). Specifically, the channel distribution unit 11 extracts the channel indicated by the main channel identification signal as a main channel from the channels constituting the input audio signal. Then, the channel distribution unit 11 outputs all the channels constituting the input audio signal and the extracted main channels to the signal level correction value calculation unit 12.

  The signal level correction value calculation means 12 performs channel number conversion of the main channel output from the channel distribution means 11 (step S102), and calculates the average loudness value of the main channel after the channel number conversion (step S103). Further, the signal level correction value calculation unit 12 performs channel number conversion of all channels output from the channel distribution unit 11 (step S104), and calculates an average loudness value of all channels after channel number conversion (step S105). .

Next, the signal level correction value calculating means 12 uses the average loudness value of the main channel after the channel number conversion, the average loudness value of all the channels after the channel number conversion, and the target loudness value, and the equation (2). Based on the above, a signal level correction value _CT is calculated (step S106).

Signal level correction value calculating means 12, among the channels which constitute the voice signal, the normal channels other than the main channel, by multiplying the calculated signal level correction value C _T, corrects the signal level of the normal channel (step S107 ). Next, the signal level correction value calculation means 12 performs channel number conversion of the main channel and the normal channel whose signal level is corrected (step S108), and calculates the average loudness value of all the channels after the channel number conversion (step S109). ).

  Next, the signal level correction value calculation means 12 determines whether or not the error between the calculated average loudness value and the target loudness value is less than a threshold value (step S110).

If it is determined that the error between the calculated average loudness value and the target loudness value is less than the threshold (step S110: Yes), the signal level correction value calculation means 12 uses the calculated signal level correction value _CT as the number of channels. Output to the conversion means 13. Number of channel conversion unit 13, among the channels constituting the audio signal, the normal channels other than the main channel, by multiplying the signal level correction value C _T output from the signal level correction value calculating means 12, normal channel signals Correct the level. Then, the channel number converting means 13 performs channel number conversion of the main channel and the normal channel with the signal level corrected, and outputs the result.

  When it is determined that the error between the calculated average loudness value and the target loudness value is not less than the threshold value (step S110: No), the signal level correction value calculation means 12 determines the main channel and the normal channel whose signal level is corrected. It is output to the channel distribution means 11 as an input signal. In response to the input from the signal level correction value calculation means 12, the channel distribution means 11 starts allocating channels, and hereinafter, the processes in steps S101 to S109 are carried out according to the average loudness value of all channels after conversion of the number of channels. Repeat until the difference from the target loudness value is less than the threshold.

  As described above, according to the present embodiment, the channel number converting apparatus 10 distributes all channels constituting the program audio to the main channel that does not adjust the signal level and the normal channel that adjusts the signal level. The number of channels of the main channel and all the channels is converted, and the average loudness value (first average loudness value) of the main channel after conversion of the number of channels and the average loudness value of the signals of all channels after conversion of the number of channels (second The difference between the target loudness value and the first average loudness value and the difference between the second average loudness value and the first average loudness value are within a predetermined range. The signal level correction value calculation means 12 for calculating the signal level correction value of the normal channel and the calculated Comprising correcting the signal level of the normal channel, the number of channel conversion unit 13 for the number of channel conversion by using a normal channel after the correction of the main channel and the signal level, the by Nos level correction value.

  The signal level of the main channel before conversion of the number of channels remains fixed, and the difference between the target loudness value and the first average loudness value and the difference between the second average loudness value and the first average loudness value are When the number of channels of program audio is converted by correcting the signal level of the normal channel so that it is within the predetermined range, the signal level of the main channel before conversion is kept constant, The average loudness value can be matched to the target loudness value

  In the present embodiment, the example in which the main channels are three channels (channels C, L, and R) has been described. However, the present invention is not limited to this, and for example, as illustrated in FIG. In addition, seven channels other than the rear channels (channels BL, BR, TpBL, TpBR) may be used as main channels.

  In FIG. 5 (f), the signal level correction value calculation means 12 performs channel C, L, R, SL, SR, TpL, TpR other than the channels BL, BR, TpBL, TpBR before and after the channel number conversion. The signal level is constant. Here, as described above, the channel SL is equally divided into the channel L ′ and the channel Ls ′. The channel SR is equally divided into the channel R ′ and the channel Rs ′. As shown in FIG. 5 (f), the signal level correction value calculation means 12 makes the signal levels of the channels SL and SR assigned to a plurality of channels constant by converting the number of channels. That is, the signal level correction value calculation means 12 allocates the audio signals of the channels allocated to the plurality of channels by the channel number conversion to the plurality of channels at the same ratio before and after the signal level adjustment. By doing so, it is possible to prevent channels allocated to a plurality of channels by channel number conversion from being heard from a direction different from that at the time of production.

  In the present embodiment, the signal level of the asserted channel is constant before and after the channel number conversion. However, the conversion of the number of channels may make it difficult to hear a dialog (for example, narration) by collecting sounds in different spatial directions in one place. Therefore, in order to make the dialog easy to hear, the overall average loudness value may be adjusted with the signal level of the normal channel after the signal level of the main channel is amplified by a predetermined coefficient.

  In the present embodiment, the description has been given using an example in which all channels constituting an audio signal are classified into two groups, ie, a main channel that does not adjust the signal level and a normal channel that adjusts the signal level. It is not limited. For example, although the signal level is changed, a quasi-main channel with a limited change width may be set, and the channels may be classified into three or more groups.

Further, as described above, the channel number conversion apparatus 10 according to the present embodiment may be incorporated in a broadcast receiver. In this case, the signal level correction value calculating means 12, instead of the target loudness value by using the average loudness value before the number of channel conversion, may calculate the signal level correction value C _T.

Specifically, the signal level correction value calculating means 12, a predetermined time from the start time of the program average loudness value (channel number before conversion of the average loudness value of all channels to (signal level correction value C _T timing for calculating a) ). Then, the signal level correction value calculation means 12 converts the difference between the recorded average loudness value before the channel number conversion and the average loudness value La (first average loudness value) of the main channel after the channel number conversion, and the channel number conversion. The difference between the average loudness value Lb (second average loudness value) of all the subsequent channels and the average loudness value La (first average loudness value) of the main channel after the number of channels conversion is within a predetermined range. and so that, to calculate a signal level correction value C _T at a given time.

As described above, the operation rules are defined so that the average loudness value throughout the program falls within the allowable range (± 1 dB) of the target loudness value (−24LKFS). Therefore, the difference between the average loudness value from the start time of the program to the predetermined time and the average loudness value La of the main channel after the channel number conversion, the average loudness value Lb of all the channels after the channel number conversion and the channel number converted as the difference between the difference between the average loudness value La of the main channel is within a predetermined range, by calculating the signal level correction value C _T, the signal level of the main channel before the channel number conversion constant While maintaining, the average loudness value of the entire program (including live broadcast programs) can be matched to the target loudness value.

  The average loudness value at each time from the start time of the program to a predetermined time can be included in, for example, a signal transmitted from a broadcasting station. In this case, the broadcast receiver can acquire the average loudness value from the start time of the program to a predetermined time by receiving the signal. When the broadcast receiver is connected to a network such as the Internet, the broadcast receiver may acquire an average loudness value from the start time of the program to a predetermined time via the network.

  The method performed in the channel number conversion apparatus 10 according to the present invention may be applied to a program for causing a computer to execute. In addition, the program can be stored in a storage medium and can be provided to the outside via a network.

  Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various variations or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, functions included in each block or step can be rearranged so as not to be logically contradictory, and a plurality of blocks or steps can be combined into one or divided.

DESCRIPTION OF SYMBOLS 10 Channel number conversion apparatus 11 Channel distribution means 12 Signal level correction value calculation means 13 Channel number conversion means

Claims (5)

A channel number conversion device for converting the channel number of program audio,
Channel distribution means for distributing all channels constituting the program audio to a main channel that does not adjust the signal level and a normal channel that adjusts the signal level;
The number of channels of each of the main channel and all the channels is converted, the first average loudness value that is the average loudness value of the main channel after the conversion of the number of channels, and the average loudness value of all the channels after the conversion of the number of channels. A second average loudness value is calculated, and a difference between a target loudness value and the first average loudness value and a difference between the second average loudness value and the first average loudness value are predetermined. Signal level correction value calculating means for calculating the signal level correction value of the normal channel so as to be within a range;
Channel number conversion for correcting the signal level of the normal channel using the signal level correction value calculated by the signal level correction value calculating means, and converting the number of channels using the main channel and the normal channel after the correction of the signal level. Means,
A channel number conversion device comprising: In the channel number conversion device according to claim 1,
The signal level correction value calculation means is characterized in that audio signals of channels allocated to a plurality of channels by channel number conversion are allocated to the plurality of channels at the same ratio before and after the signal level adjustment. Channel number conversion device. In the channel number conversion device according to claim 1 or 2,
The signal level correction value calculation means calculates a difference between the target loudness value and the second average loudness value when channel number conversion is performed using a normal channel whose signal level is corrected by the calculated signal level correction value. When the difference does not become less than the threshold value, the calculation of the signal level correction value is repeated using the main channel and the normal channel after the correction of the signal level. A broadcast receiver comprising the channel number conversion device according to any one of claims 1 to 3,
The signal level correction value calculating means records the average loudness value before the channel number conversion from the start time of the program to a predetermined time, and the recorded average loudness value before the channel number conversion and the first average loudness value. And a signal level correction value at the predetermined time is calculated so that a difference between the difference between the second average loudness value and the difference between the second average loudness value and the first average loudness value is within a predetermined range. Broadcast receiver.   The program for functioning a computer as a channel number conversion apparatus as described in any one of Claim 1 to 3.

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