CN111696563B - Loudness equalization method based on audio decoder, decoder and Bluetooth device - Google Patents
Loudness equalization method based on audio decoder, decoder and Bluetooth device Download PDFInfo
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/16—Vocoder architecture
- G10L19/167—Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/03—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 characterised by the type of extracted parameters
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/48—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 specially adapted for particular use
- G10L25/51—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 specially adapted for particular use for comparison or discrimination
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
- H03G3/20—Automatic control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/436—Interfacing a local distribution network, e.g. communicating with another STB or one or more peripheral devices inside the home
- H04N21/4363—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network
- H04N21/43637—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network involving a wireless protocol, e.g. Bluetooth, RF or wireless LAN [IEEE 802.11]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
- H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
- H04N21/439—Processing of audio elementary streams
Abstract
The invention discloses a loudness equalization method based on an audio decoder, the audio decoder and Bluetooth equipment, and belongs to the technical field of digital signal processing. The loudness equalization method based on the audio decoder comprises the following steps: counting a first loudness and effective measurement times of the first audio decoding signal, and calculating a first effective loudness; calculating a first loudness and a second loudness of a second audio decoded signal; counting the measurement output values of the first loudness and the second loudness of the second audio decoding signal as the third loudness of the second audio decoding signal, and judging the size relation between the third loudness and the first effective loudness; and calculating corresponding loudness variation gain according to the loudness adjustment amplitude, and adjusting the loudness of the second audio coding signal according to the loudness variation gain. The application of the invention ensures the consistency of loudness when switching audio and video programs and avoids frequent loudness adjustment.
Description
Technical Field
The invention relates to the technical field of digital signal processing, in particular to a loudness equalization method based on an audio decoder, the audio decoder and Bluetooth equipment.
Background
Currently mainstream bluetooth audio decoders include: SBC audio decoders, which are mandated by the A2DP protocol and are most widely used; the AAC-LC audio decoder has good tone quality and wide application range, and is supported by a plurality of mainstream mobile phones; the aptX series audio decoder has good tone quality, but high code rate, is a unique technology for high pass, and is relatively closed; the LDAC audio decoder has good sound quality, but high code rate, is a unique technology of Sony, and is also closed. Based on the above reasons, the Bluetooth international association Bluetooth Sig has introduced the LC3 audio codec in conjunction with numerous manufacturers, which has the advantages of low delay, high sound quality and no special fee in the Bluetooth field, and is paid attention by the manufacturers
An important application in the field of bluetooth low energy is bluetooth music headsets, which are used to enjoy music. In general, there are many formats of music, such as mp3, AAC, WMA, RA, wav, FLAC, OGG, vorbis, OPUS, and the like, which are formats that conventional music players support. The different formats of music may be produced by different manufacturers, and their loudness levels are different, and when music playing is switched, users are often required to manually adjust the volume, which causes inconvenience to users, and there may be danger in some scenes, such as driving a car, to manually adjust the volume of music.
Similar scenes appear in the television field. At present, the average loudness difference between each television channel in China is large, for example, high-definition channels of central vision and each province satellite vision adopt a dolby AC-3 coding standard and use a dolby 'white-to-one' technology, but the highest difference of description values of the 'white-to-one' of the high-definition channels of each province is 7LKFS, while each standard-definition channel adopts an MPEG coding technology and does not use the 'white-to-one' technology of the dolby. Therefore, in the current state, the central viewing channel has better control on loudness, the consistency of the loudness of each channel is higher and is basically about-24 LKFS, and the loudness difference of each province station is larger. According to statistics, the difference between the maximum and minimum values of the loudness of each province station in 30 days is about 6LKFS, which causes that the sound of a user is suddenly large and small when the user switches a television program, and the user experience is seriously influenced.
Disclosure of Invention
In view of the above technical problems in the prior art, the present invention provides a loudness equalization method based on an audio decoder.
In one aspect of the present invention, a loudness equalization method based on an audio decoder is provided, which includes the steps of calculating a first effective loudness: measuring the loudness of the first audio decoding signal, calculating and storing a first effective loudness according to the effective loudness value and the effective measurement times of the first audio decoding signal; and (3) loudness statistics step: measuring the first loudness of the second audio decoding signal when the number of buffering frames of the second audio decoding signal is greater than or equal to the loudness calculation length, and measuring the second loudness of the second audio decoding signal when the number of buffering frames of the second audio decoding signal is less than the loudness calculation length and the loudness adjustment is performed on the second audio decoding signal; judging loudness: taking the first loudness of the second audio decoding signal or the measured output value of the second loudness as the third loudness of the second audio decoding signal, starting loudness adjustment when the third loudness exceeds the first range of the first effective loudness, lowering the loudness of the second audio decoding signal when the third loudness is greater than the upper limit of the second range of the first effective loudness, raising the loudness of the second audio decoding signal when the third loudness is less than the lower limit of the second range of the first effective loudness, and ending the loudness adjustment when the third loudness is greater than or equal to the lower limit of the second range and less than or equal to the upper limit of the second range; and an updated audio decoding step: it comprises a loudness equalization process on the second audio decoded signal, wherein the loudness equalization process comprises: calculating corresponding loudness variation gain according to the loudness adjustment amplitude; the loudness of the second audio decoded signal is adjusted according to the loudness variation gain.
In another aspect of the present invention, an audio decoder is provided, wherein the audio decoder is operative to perform any one of the first aspect to the audio decoder based loudness equalization method.
In another aspect of the present invention, a bluetooth device is provided, including but not limited to a BR/EDR bluetooth device or a bluetooth low energy device, which includes: an audio decoder, wherein the audio decoder is operative to perform any of the first schemes based on the audio decoder's loudness equalization method.
The beneficial effects of the invention are: when the method is applied, the loudness consistency is ensured and frequent loudness adjustment is avoided when the audio and video programs are switched.
Drawings
Fig. 1 is a schematic flow chart of an embodiment of the loudness equalization method based on an audio decoder according to the present invention;
FIG. 2 is a schematic diagram of the measurement of one embodiment of the first loudness and the second loudness of the present invention;
FIG. 3 is a schematic diagram of one embodiment of the first loudness and the second loudness of the present invention;
FIG. 4 is a schematic flow chart illustrating the calculation of a first effective loudness level according to an embodiment of the present invention;
fig. 5 is a schematic diagram of one embodiment of a first loudness threshold and a second loudness threshold in accordance with the invention;
fig. 6 is a flow chart illustrating one embodiment of the loudness equalization method based on an audio decoder according to the present invention;
FIG. 7 is a schematic diagram illustrating the overall control flow of one embodiment of the audio decoder-based loudness equalization method of the present invention;
fig. 8 is an application example of the loudness equalization method based on an audio decoder of the present invention;
fig. 9 is an application example of the loudness equalization method based on an audio decoder of the present invention.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will make the advantages and features of the invention easier to understand by those skilled in the art, and thus will clearly and clearly define the scope of the invention.
It is to be understood that the terms first and second in the claims and description of the invention are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In order to facilitate understanding of the loudness equalization method based on the audio decoder, the following description takes the audio loudness adjustment of the cable television, the set-top box and the bluetooth speaker, in combination with the LC3 audio decoder, and takes monaural audio transmission as an example. It should be noted that the loudness equalization method based on the audio decoder of the present invention is also applicable to other platforms based on the bluetooth technology, such as a combination of a music player and a bluetooth headset; the same applies to other audio decoder platforms, such as AAC audio decoders; the invention is also applicable to the audio transmission process of multi-channel.
In one embodiment of the present invention, fig. 1 shows a schematic flow chart of one embodiment of the loudness equalization method based on an audio decoder of the present invention, and in this embodiment, the loudness equalization method based on the audio decoder of the present invention comprises the following steps:
step S101: a step of calculating a first effective loudness.
In one embodiment of the present invention, the loudness of the first audio decoded signal is measured, and the first effective loudness is calculated and stored according to the effective loudness measurement value and the effective measurement times of the first audio decoded signal.
In one example of the present invention, an initialization step is required before the step of calculating the first effective loudness is performed. In this step, the loudness equalization indication parameter is set to 0, indicating that the loudness of the current audio decoded signal does not need to be adjusted. In addition, when the loudness equalization indication parameter is 1, the loudness of the current audio decoding signal is required to be increased and adjusted, and when the loudness equalization indication parameter is-1, the loudness of the current audio decoding signal is required to be decreased and adjusted. In the initialization step, a loudness threshold value is set as a first loudness threshold, the frequency statistics of the third loudness is set as 0, and the sum of the effective loudness is set as 0; the loudness equalization factor is set to 1; the loudness equalization state parameter is set to 0, indicating that the loudness equalization process has not been performed yet, and in addition, when the loudness equalization state parameter is 1, indicating that the loudness equalization process is in progress.
In one example of the present invention, a 400ms block gating of audio data is used for the loudness measurement process of an audio decoded signal. Wherein it is determined whether the buffered first audio decoding signal data length reaches the expected loudness calculation length based on the 400ms audio data block strobe according to standard specifications. In this example, the loudness calculation length may be 400ms, and the measurement interval may be calculated as 100ms, based on the superposition of 75% of the measurement range. When the buffered first audio decoding signal data length reaches the expected loudness calculation length, for example, the length of the buffering frame number is 400ms, the first loudness of the first audio decoding signal is calculated, wherein when the first loudness of the first audio decoding signal is calculated, the measurement process of the first loudness is performed at intervals of 100ms according to the relevant parameters of the 400ms audio data block gating. The first loudness of the audio decoding signal is measured, and the rough change of the loudness of the audio decoding signal is counted in a larger time interval.
In an embodiment of the present invention, when the audio/video system is in a process of starting, shutting down or audio switching, the loudness is gradually increased or decreased, the loudness counting step is not performed. In the actual loudness measurement process, there may be a situation where the loudness of the audio signal gradually increases or gradually decreases, and in order to avoid an error in loudness measurement, the loudness measurement and adjustment process is not performed at this time. For example, the set-top box may have a Ramping up loudness boost on audio loudness during a cable television just powered on or during a television channel change. Assuming that the time of the Ramping up-up process is N seconds, the loudness measurement is not performed for this N second time.
In this embodiment, when the electronic device running the audio decoder is first powered on and running and calls the audio decoder, the loudness equalization step is not required, and the loudness equalization indication parameter is zero. As can be seen from fig. 2, the first audio decoded signal now only performs a first loudness measurement. And measuring the first loudness and calculating the first effective loudness on the basis that the number of the buffer frames meets the loudness calculation length.
In one example of the present invention, L effective measurements are performed in the first audio decoded signal, and the first effective loudness is calculated by the following formula:
wherein, for the effective measurement times L, according to the relevant standard, in order to prevent the excessive influence of the special material of the audio-video program, such as the low-volume sound background of the program, long-time silence, etc., on the loudness of the program, taking the gating of the 400ms audio data block as an example, 400ms and 75% overlap as the measurement length of each time when measuring the loudness, as shown in fig. 3. For example, in the loudness equalization method based on the audio decoder, the minimum value of the effective measurement times L is 200, and the measurement is easily inaccurate due to too small selection value. At this time, the corresponding length of the audio/video program is 20.3 seconds, if the number of measurement times is small, the duration of the corresponding program is short, the measured effective loudness is inaccurate, and the subsequent loudness adjustment is influenced. And finally, storing the calculated first effective loudness. The flow of calculating the first effective loudness is schematically shown in fig. 4.
On the basis of taking a cable television, a set top box and a Bluetooth sound box as a loudness adjustment platform, when the loudness equalization method based on the audio decoder is operated for the first time, a user adjusts the loudness by adjusting a volume adjustment module of the set top box or the Bluetooth sound box, so that the loudness suitable for the user is achieved. And recording the loudness value suitable for the user in the current audio and video program through the calculation of the first effective loudness, and providing reference for subsequent loudness adjustment.
In one example of the present invention, the step of calculating the first effective loudness is not performed when the first effective loudness is set to a fixed value. The loudness equalization method based on the audio decoder comprises a fixed loudness output mode and an average loudness output mode. In the fixed loudness output mode, the first effective loudness value is a fixed value and is a default loudness standard value suitable for most crowds, and in the subsequent loudness equalization process, loudness adjustment is carried out according to the fixed effective loudness value, the subsequent fixed effective loudness value cannot be dynamically changed, and the fixed effective loudness value can be reset only when a user actively modifies the value. For example, the first effective loudness may be set to-24 LKFS based on the "loudness Specification for Sound production of television programs" made by Central television stations in China and the "Algorithm for measuring loudness of Audio programs and true Peak Audio levels" of the International telecommunication Union Standard ITU-R BS.1770-4.
In the average loudness output mode, when loudness equalization is performed for the first time, measurement and calculation of the first effective loudness are required, and the calculation is described above. In the subsequent loudness adjustment process, except that the audio decoder adjusts the loudness of the decoded signal according to the effective loudness value so as to meet the requirements of users, the users can manually adjust the loudness of the audio output end according to the requirements of the real environment condition or program effect. It should be noted that the user manually adjusts the loudness of the volume, which is different from the loudness equalization method in the audio decoder according to the present invention. For example, in the loudness equalization method based on the audio decoding decoder, the input audio signals with different loudness are equalized and adjusted in the loudness range suitable for users, such as the audio signals of different channels of a television. If the noise of the surrounding environment is increased, the user can also adjust the loudness through adjusting the audio output equipment, such as a sound box, so that the user experience is ensured, and the personalized needs of the user are met.
Step S102: and (5) loudness statistics.
In one embodiment of the present invention, a first loudness of the second audio decoded signal is measured when the number of buffered frames of the second audio decoded signal is greater than or equal to the loudness calculation length, and a second loudness of the second audio decoded signal is measured when the number of buffered frames of the second audio decoded signal is less than the calculation length and the loudness adjustment is performed on the second audio decoded signal.
When the electronic device including the audio decoder is powered on again, the first effective loudness is assumed to be successfully counted and updated in the last power-on operation, and if the first effective loudness is not updated last time, the first effective loudness is counted again. After the audio decoder is started, initialization is needed, and at the moment, the loudness equalization indication parameter is zero.
Fig. 2 is a schematic diagram of the measurement of one embodiment of the first loudness and the second loudness of the present invention. As shown in fig. 2, it is first determined whether the number of buffered frames of the second audio decoded signal is the loudness calculation length. Taking the gating of a 400ms audio data block as an example, when the number of buffering frames is less than 400ms, loudness measurement is not carried out, when the number of buffering frames meets 400ms, first loudness measurement is carried out, and when the number of buffering frames meets 100ms on the basis of 400ms, the first loudness measurement is continued; and when the buffering frame number is less than 100ms on the basis of 400ms and the loudness equalization indication parameter is nonzero, namely the loudness of the second audio decoding signal needs to be adjusted, measuring the second loudness. Wherein fig. 3 shows a schematic diagram of one specific embodiment of the first loudness and the second loudness in the present invention. As can be seen from fig. 3, the measurement interval of the first loudness is significantly longer than the measurement interval of the second loudness, so the measurement of the first loudness is coarser and the measurement of the second loudness is more precise. When loudness measurement is performed, the statistical basic unit of loudness is M seconds, wherein M can be 0.4 seconds, 0.6 seconds, and 0.8 seconds according to ITU-R bs.1770-4, the algorithm for measuring loudness of audio programs and true peak audio levels. In an example of the present invention, when the electronic device running the audio decoder is powered on again and the audio decoder is called, in the initialization process, the loudness equalization indication parameter is zero, the audio decoder starts decoding the audio signal, and the loudness equalization method based on the audio decoder starts running. As shown in fig. 2, when the number of buffer frames is satisfied as the loudness calculation length, the measurement of the first loudness of the second audio decoded signal is started. And comparing the first loudness value of the second audio decoding signal with the first effective loudness value obtained by the first audio decoding signal, and adjusting the loudness equalization indication parameter to be in a non-zero state of +1 or-1 when the loudness equalization adjustment is required. In the loudness measurement of the second audio decoded signal, when the number of buffer frames is lower than the loudness calculation length and the loudness equalization indication is non-zero, as shown in fig. 2, the second loudness of the second audio decoded signal is measured at this time.
By taking the first loudness and the second loudness into full consideration in the loudness measurement process, it is ensured that the loudness of the decoded audio can be measured sufficiently also when the decoded audio is short. When the loudness needs to be adjusted, namely the loudness balance indication parameter is not zero, the second loudness with smaller measurement time interval is measured, so that the change of the loudness of the audio signal can be grasped, the accuracy of audio adjustment is improved, and the user experience is improved. The first loudness and the second loudness are measured respectively, the rapidity of loudness measurement and the accuracy of loudness measurement are fully considered, and the accuracy of subsequent audio loudness equalization adjustment is guaranteed.
Step S103: and judging the loudness.
In one embodiment of the present invention, the measured output value of the first loudness or the second loudness of the second audio decoded signal is used as the third loudness of the second audio decoded signal, loudness adjustment is started when the third loudness exceeds the first range of the first effective loudness, the loudness of the second audio decoded signal is decreased when the third loudness is greater than the upper limit of the second range of the first effective loudness, the loudness of the second audio decoded signal is increased when the third loudness is less than the lower limit of the second range of the first effective loudness, and loudness adjustment is ended when the third loudness is greater than or equal to the lower limit of the second range and less than or equal to the upper limit of the second range.
In one example of the present invention, the first range upper limit is a sum of the first effective loudness and a first loudness threshold, the first range lower limit is a difference between the first effective loudness and the first loudness threshold, the second range upper limit is a sum of the first effective loudness and a second loudness threshold, and the second range lower limit is a difference between the first effective loudness and the second loudness threshold, where the first loudness threshold is greater than the second loudness threshold. And a first range and a second range of the first effective loudness are introduced, so that when the loudness of the current audio and video program needs to be adjusted, the problems that the loudness is adjusted frequently due to too small loudness adjustment, the system load is increased, or the user has obvious feeling and the user experience is influenced due to too large loudness adjustment are avoided.
In one example of the present invention, fig. 5 is a schematic diagram of one embodiment of the first and second loudness thresholds of the present invention. In this example, the loudness measurement is performed on the second audio decoded signal, and the measurement method and process are as described in step S102. Taking the measured output value of the first loudness or the second loudness of the second audio decoding signal as the third loudness of the second audio decoding signal, and when the third loudness is greater than the sum of the first effective loudness and the first loudness threshold or less than the difference between the first effective loudness and the first loudness threshold, beginning loudness adjustment; adjusting the loudness of the second audio decoding signal low when the third loudness is greater than the sum of the first effective loudness and the second loudness threshold, and adjusting the loudness of the second audio decoding signal high when the third loudness is less than the difference between the first effective loudness and the second loudness threshold; and after the loudness adjustment, when the third loudness is more than or equal to the difference value between the first effective loudness and the second loudness threshold and less than or equal to the sum value of the first effective loudness and the second loudness threshold, ending the loudness adjustment. The first loudness threshold is a starting loudness equalization threshold, the second loudness threshold is an ending loudness equalization threshold, and the first loudness threshold is larger than the second loudness threshold.
The process is described in detail below with specific examples. For example, the first loudness threshold may take a value of 2Lu, the second loudness threshold may take a value of 1Lu, and the first effective loudness threshold may take a value of-24 Lu. When the loudness of the audio decoding signal is-21 Lu, the loudness is larger than the sum of the first effective loudness and the first loudness threshold, namely-22 Lu, and the loudness of the audio decoding signal needs to be reduced in the subsequent loudness equalization adjustment process; when the loudness of the audio decoding signal is-25.5 Lu, the loudness is not less than-26 Lu which is the difference between the effective loudness and the first loudness threshold, and the loudness of the audio decoding signal does not need to be subjected to an equalization adjustment process; and when the loudness of the audio decoding signal after equalization adjustment is-22.5 Lu which is larger than the sum of the first effective loudness and the second loudness threshold being-23 Lu, further loudness reduction adjustment is required, and when the loudness of the audio decoding signal after equalization adjustment is-23.5 Lu which is smaller than the sum of the first effective loudness and the second loudness threshold being-23 Lu and larger than the difference of the first effective loudness and the second loudness threshold being-25 Lu, the loudness of the audio decoding signal meets the adjustment requirement, and the loudness equalization adjustment process is ended at this moment.
Step S104: an updated audio decoding step comprising a loudness equalization process on the second audio decoded signal.
In this particular embodiment, the loudness equalization process on the second audio decoded signal comprises: and calculating corresponding loudness variation gain according to the loudness adjustment amplitude, and adjusting the loudness of the second audio decoding signal according to the loudness variation gain. The loudness adjustment amplitude can be an expected value of loudness adjustment change of the audio signal within one second, and then the one-second loudness change gain of the audio decoding signal is calculated according to the one-second loudness adjustment amplitude, and then the loudness of the second audio decoding signal is adjusted according to the loudness change gain.
In a specific embodiment of the present invention, adjusting the loudness of the second audio decoded signal according to the loudness variation gain comprises: obtaining a frame of loudness variation gain of the second audio decoding signal according to the loudness variation gain and the frame length mapping of the second audio decoding signal; amplifying or reducing and adjusting the first loudness equalization factor according to the loudness variation gain of one frame to obtain a second loudness equalization factor; and adjusting the loudness of one frame of audio decoding data of the second audio decoding signal according to the second loudness equalization factor. And obtaining the one-frame loudness variation gain of the second audio decoding signal according to the set one-second loudness variation gain and the frame length mapping of the second audio decoding signal. And then the gain adjustment degree balance factor is changed according to the loudness of one frame, so that the loudness of the second audio decoding signal is adjusted.
In an example of the present invention, when the loudness of the second audio decoding signal is equalized in the updated audio decoding step, a loudness variation gain corresponding to the loudness adjustment amplitude of the audio decoding signal is first determined, and a specific loudness variation gain value may be obtained by offline calculation in advance. Wherein the loudness adjustment amplitude value can be selected within one second of the time. For example, if the loudness of the desired signal increases or decreases by 2Lu within one second, the loudness variation gain value can be obtained by off-line calculation, and in order to prevent the drastic change of the signal level from affecting the user experience during the actual operation, a smaller signal gain step size can be set, so that the amplitude of each adjustment is smaller. Wherein, the selection of the signal gain step size can be obtained by in-line simulation. The following description is given by way of example.
In this example, an audio test file is selected, its average loudness is calculated, and another file is generated based on this file such that the difference between the obtained average loudness of the other file and the average loudness of the first file is 1LKFS or-1 LKFS. Since the human ear perceives loudness changes in the order of 1 second, the difference between the average loudness of the second file and the average loudness of the first file is brought to the desired value by adjusting the gain step size in one second. Since the loudness calculation is related to the signal level and the frequency distribution, when the gain step calculated off-line based on a certain audio decoding signal is actually used, the loudness equalization speed for other audio decoding signals has deviation, but because the human ear feels about 1 second of loudness change, the actual application is not affected.
In the loudness equalization method based on the audio decoder, preferably, the typical loudness difference threshold is 2LKFS, so the aim of performing the off-line simulation is to obtain the change gain of the loudness equalization change of 2LKFS within 1 second. By limiting the adjustment amplitude during loudness equalization adjustment, overflow caused by overlarge adjustment amplitude of the loudness of the audio signal is avoided, and the situation that the user experience is reduced due to violent change of the loudness is avoided.
In one embodiment of the present invention, the corresponding gain change is calculated according to the determined one-second loudness adjustment amplitude of the audio decoding signal, and then mapped to obtain the one-frame loudness change gain of the audio decoding signal in the audio decoder. Taking the LC3 audio decoder as an example, when the audio decoding signal is 10ms frame length, the calculation formula of the loudness variation gain of one frame is:
Loudness_gain_1frame = Loudness_gain_1sec/A
when the audio decoded signal is 10 msec frame length, the a value is 100. Wherein, loudness _ gain _1frame represents the Loudness variation gain of one frame of the audio decoding signal, and Loudness _ gain _1sec represents the Loudness variation gain of one second of the audio decoding signal. When the loudness variation gain of one frame of the audio decoding signal is calculated, the denominator in the formula is adjusted according to the frame length of the audio decoding signal, wherein A = 1000/frame length. For example, when the audio decoded signal is 7.5 msec frame length, a takes a value of 1000/7.5=133.
In this example, the loudness of the audio decoding signal is, for example, -30Lu, and if the one-second loudness adjustment amplitude is determined to be 6Lu, the corresponding gain variation is about 0.2 according to the results of the offline simulation. Since the aim of loudness adjustment is to adjust the loudness to-24 Lu, the loudness needs to be adjusted up step by step, and then the one-second loudness gain target of the audio decoding signal is 1+ (0.2) =1.2, that is, the loudness of the audio signal is adjusted to 120% of the original loudness. For an LC3 audio decoder, a loudness variation gain of one frame may be 0.2/100=0.002, i.e. 1.000,1.002,1.004, \8230;, 1.200 for audio with a 10ms frame length.
In an embodiment of the present invention, the first loudness equalization factor is scaled up or down according to the obtained loudness variation gain of the frame, so as to obtain the second loudness equalization factor. Wherein, the first loudness equalization factor can be set to 1 in the initialization process, and the second loudness equalization factor can be represented by the sum or difference of the first loudness equalization factor and the loudness variation gain of one frame. The second loudness factor is adjusted to a sum of the first loudness factor and the one frame loudness variation gain when the loudness is up adjusted and to a difference of the first loudness factor and the one frame loudness variation gain when the loudness is down adjusted.
In this example, for an audio decoding signal of 10ms frame length of the LC3 audio decoder, for example, when the one-second loudness adjustment amplitude is 6LKFS and the loudness of the second audio decoding signal is-30 LKFS, the corresponding one-second loudness variation gain is about 0.2 and the one-frame loudness variation gain is 0.2/100=0.002, depending on the results of the off-line simulation. When the loudness of the second audio decoding signal needs to be increased, the second loudness equalization factor is 1+0.002=1.002, and then the loudness of one frame of audio decoding signal is adjusted; when the loudness of the second audio decoded signal needs to be reduced, the second loudness equalization factor is 1-0.002=0.998, and then the loudness of one frame of the audio decoded signal is adjusted.
In one example of the present invention, the loudness of the second audio decoded signal is adjusted by raising or lowering the loudness of one frame of audio decoded data of the second audio decoded signal according to the second loudness equalization factor. Taking an audio decoding signal with a frame length of 10ms of an LC3 audio decoder, the loudness adjustment amplitude for one second is 6LKFS, and the loudness of the second audio decoding signal is-30 LKFS as an example, through the above calculation of the second loudness equalization factor, when the loudness needs to be increased, the second loudness equalization factor is 1+0.002=1.002, and when the loudness needs to be decreased, the second loudness equalization factor is 1-0.002=0.998. And then carrying out loudness adjustment on the loudness of the frame of audio data according to the second loudness equalization factor. When loudness is increased, the result of one second loudness adjustment is-24 LKFS; the result of the one second loudness adjustment when reducing loudness was-36 LKFS. Through the adjustment of multiframe loudness, the violent change of loudness is avoided, and user experience is improved.
In this example, when the loudness of the second audio decoding signal is adjusted by the second loudness equalization factor, taking the audio decoding signal with the length of 10ms of the LC3 audio decoder, the one-second loudness adjustment amplitude is 6LKFS, and the loudness of the second audio decoding signal is-30 LKFS as an example, when the loudness of the second audio decoding signal is increased, the ideal loudness adjustment result is that the loudness of the second audio decoding signal is adjusted from-30 LKFS to-24 LKFS by adjusting the loudness of the second audio decoding signal per frame in one second. However, the specific loudness adjustment procedure is a non-strictly linear variation, so the following loudness adjustment cases arise:
1. the loudness adjustment process is strictly linear. At this time, the loudness adjustment amplitude for one second is 6LKFS, and according to the result of the off-line simulation, the corresponding loudness variation gain for one second is about 0.2, and the loudness variation gain for one frame is 0.2/100=0.002, and the second loudness equalization factors are sequentially 1.002,1.004,. 1.2 when the loudness of each frame is adjusted. When the loudness adjustment process is in a strict linear relation, the loudness adjustment result after one second is-24 LKFS, which is very special and difficult to realize in the actual loudness adjustment process.
2. The loudness adjustment process is a non-strict linear relationship. At this time, the loudness adjustment process is no longer strictly changed according to the predetermined loudness adjustment gain, and the loudness of the second audio decoded signal is adjusted to-24 LKFS already by-30 LKFS, possibly when the adjustment time is less than one second. During the loudness adjustment in frames, a new loudness is calculated every frame, and if a predetermined adjustment target has been reached within one second, the loudness adjustment may be ended. Wherein in the inventive audio decoder based loudness equalization method the above mentioned loudness adjustment procedure is supported.
3. The loudness adjustment process is not strictly linear, and at this time, the loudness adjustment process does not strictly change according to the preset loudness adjustment gain any more, and the loudness of the second audio decoding signal is adjusted from-30 LKFS to-24 LKFS after one second, possibly. During the loudness adjustment in frames, a new loudness is calculated for each frame, and if the predetermined adjustment target is not reached within one second, the loudness adjustment is continued for the next second until the target position is reached. Wherein in the inventive audio decoder based loudness equalization method the above mentioned loudness adjustment procedure is supported.
In the specific loudness adjustment process, the loudness of one frame of audio decoding signal is adjusted, and then the adjustment of the whole audio decoding signal is realized. Because the non-linear adjustment process of the loudness adjustment of each frame makes the loudness adjustment value of the frame of audio decoding signal greater than or less than the preset loudness adjustment value when the loudness of the frame of audio decoding signal is adjusted, it is possible to adjust the loudness of the audio decoding signal to the preset loudness adjustment amplitude of one second in less than one second, more than one second, or just one second. The loudness equalization method based on the audio decoder supports various practical loudness adjustment processes.
In one example of the present invention, fig. 6 shows a flow chart of one embodiment of the loudness equalization method based on an audio decoder according to the present invention. Wherein the process shown in fig. 6 is a schematic diagram of a loudness equalization flow for a second audio decoded signal. When the audio-based decoder loudness equalization method is carried out for the first time, the first effective loudness is obtained according to the calculation process of the first effective loudness of the first audio decoding signal and is used as the loudness standard for adjusting the loudness of the subsequent second audio decoding signal.
In this example, when the audio system is first powered on and the first effective loudness calculation is not performed, it is determined whether the measured first loudness value or the second loudness value is a mute value. The mute value here represents a valid loudness value preset during initialization, for example-70 LKFS, which represents muting or very low volume at that time. When the first loudness value or the second loudness value is a mute value, the equalization adjustment process of the loudness is not performed at this time.
As shown in fig. 6, the first loudness or the second loudness of the second audio decoded signal is calculated according to the above-described loudness calculation method, and the measurement results of the first loudness and the second loudness are output as the third loudness of the second audio decoded signal. When the third loudness of the second audio decoding signal is larger than the sum of the first effective loudness and the first threshold or smaller than the difference of the first effective loudness and the first threshold, performing subsequent loudness equalization operation; when the third loudness of the second audio decoding signal is greater than or equal to the difference between the first effective loudness and the second threshold and less than or equal to the sum of the first effective loudness and the first threshold, the subsequent loudness equalization adjustment operation is not needed.
In this example, the loudness equalization state parameter may take a value of 0 or 1, and when the initialization is performed, the loudness equalization state parameter is set to 0, which indicates that loudness equalization has not been performed yet, and when the loudness equalization state parameter is set to 1, which indicates that a loudness equalization operation is now being performed. As shown in fig. 6, when the loudness equalization operation is not performed, the loudness equalization state parameter is set to 0, and the loudness threshold value is set to the first loudness threshold value at this time, so as to determine whether the loudness adjustment of the second audio decoding signal starts or not; and in the loudness equalization operation process, setting the loudness equalization state parameter to be 1, setting the loudness threshold value to be a second loudness threshold value at the moment, judging whether the loudness equalization adjustment of the second audio decoding signal meets the adjustment requirement, and ending the loudness equalization adjustment process when the loudness after the equalization adjustment is smaller than or equal to the sum of the first effective loudness and the second loudness threshold and is larger than or equal to the difference between the first effective loudness and the second loudness threshold.
In the adjusting process, according to the third loudness of the second audio decoding signal output by the loudness measuring module, the third loudness is taken as an object of loudness equalization adjustment, then loudness equalization adjustment judgment is carried out, when the third loudness is larger than the sum of the first effective loudness and the first loudness threshold, the loudness equalization indication parameter is set to be-1, and the third loudness value is subjected to reduced loudness equalization operation; when the third loudness is smaller than the difference value between the first effective loudness and the first loudness threshold, setting the loudness equalization indication parameter to be +1, and performing loudness equalization operation for increasing the third loudness value; for other cases, the third loudness value is not loudness adjusted, and the loudness equalization indicator parameter is set to 0. Similarly, when the loudness threshold is set to be the second loudness threshold, and when the third loudness is greater than the sum of the first effective loudness and the second loudness threshold, the loudness equalization indication parameter is set to be-1, and the loudness equalization operation of reducing the third loudness value is performed; when the third loudness is less than the difference between the first effective loudness and the second loudness threshold, setting the loudness equalization indication parameter to +1, and performing an increased loudness equalization operation on the third loudness value; and for other cases, the loudness equalization indication parameter is set to 0, which indicates that the loudness adjustment meets the loudness requirement at the moment, and the loudness equalization adjustment operation is finished.
In an example of the present invention, when the loudness equalization method based on an audio decoder according to the present invention is in a usage scenario of an average loudness mode, when the second audio decoding signal is in a non-loudness increasing stage, that is, a non-loudness Ramping up stage or a non-loudness decreasing Ramping down stage, the third loudness after loudness equalization is added at this time, and the number of times of measurement of the third loudness is counted, and a new effective loudness is calculated according to the above-mentioned calculation method of the first effective loudness. In an example of the present invention, after the normal playing of the current audio/video program is finished, the new second effective loudness replaces the original first effective loudness. In this example, when an abnormal ending of the current audio-video program occurs, such as a power failure, or the number of loudness statistics does not meet the measurement limit, the effective loudness is not replaced.
In an embodiment of the present invention, fig. 7 is a schematic diagram of an overall control flow of the loudness equalization system of the present invention, and as shown in fig. 7, when the loudness equalization system of the present invention is started, an initialization operation is required, where a loudness equalization indication parameter is set to 0, which indicates that no loudness equalization is performed; initializing a loudness threshold to be a first loudness threshold, and judging whether to start loudness equalization operation; the effective loudness counting times and the effective loudness sum in the loudness counting parameter are set to be 0; the loudness equalization factor is set to 1, which indicates that no loudness equalization operation is performed at this time; the loudness equalization state parameter is set to 0, indicating that a loudness equalization operation is not in progress.
In one example of the present invention, the updated audio coding module shown in fig. 7 performs primarily the loudness equalization operation on the audio signal, where the module does not operate when the loudness equalization system of the present invention is first turned on.
Fig. 7 is a schematic diagram illustrating the overall control flow of a specific example of the loudness equalization method based on an audio decoder according to the present invention. In the loudness measurement process, a first loudness or a second loudness of the audio decoding signal is measured, wherein in calculating the first loudness, loudness calculation is performed at large time intervals based on 400ms audio data block gating according to standard specifications for counting coarse changes in loudness. And when the data length of the buffered audio decoding signal does not reach the expected loudness calculation length and the loudness of the audio decoding signal needs to be adjusted, calculating the second loudness of the second audio signal, wherein when the second loudness is calculated, the loudness calculation is carried out at a smaller time interval based on 400ms audio data block gating according to standard regulation, and is used for counting the accurate change of the loudness. And counting the measurement output values of the first loudness and the second loudness of the second audio decoding signal as the third loudness of the second audio decoding signal, counting the value and the effective measurement times of the third loudness, summing the third loudness and calculating the average value to obtain an effective loudness value for loudness adjustment, wherein the effective loudness value is used as a loudness standard value for carrying out loudness equalization adjustment work in the updated audio decoding process. After all audio frame decoding is completed, for example, after the television is turned off, the effective loudness value is stored. When the loudness equalization method based on the audio decoder is carried out for the second time, the updated audio decoding process carries out loudness equalization adjustment operation according to the last effective loudness value, at the moment, the loudness equalization indication and effective loudness counting module continues to carry out the counting and calculation process of the effective loudness, after all audio frame decoding is finished, the newly generated effective loudness is stored to replace the original effective loudness, and the new effective loudness is used as a new loudness standard in the updated audio decoding process to carry out subsequent loudness equalization adjustment work.
In one example of the present invention, fig. 8 shows an application example of the loudness equalization method based on an audio decoder according to the present invention. The audio decoder based loudness equalization method of the present invention is located in an audio decoder in a bluetooth receiver. In the example of a cable television, a set-top box and a bluetooth speaker, a user may adjust the volume through a volume adjustment module a in the set-top box and a volume adjustment module B in the bluetooth receiver, wherein an audio decoder including loudness equalization in the bluetooth receiver is the content of the present invention, and automatically adjusts the loudness. In the working process of the loudness equalization method based on the audio decoder, a user can adjust the volume through the volume adjustment module B according to own preference, or current program effect, environmental factors and the like, namely, the volume of the Bluetooth sound box can be adjusted through means of remote control and the like, so that the situation that the volume needs to be increased to meet the requirement when environmental noise is increased is realized, the personalized adjustment of the loudness is also realized, and the use experience of the user is improved.
In one example of the present invention, fig. 9 shows an application example of the loudness equalization method based on an audio decoder according to the present invention. Fig. 9 shows specific positions of the loudness equalization method based on the audio decoder in the decoding process of the audio decoder when the loudness equalization method based on the audio decoder is implemented. The "loudness equalization" module of the gray portion in fig. 9 is used to execute the loudness equalization method based on the audio decoder according to the present invention.
In one embodiment of the present invention, the audio decoder of the present invention is operative to perform the method for audio decoder based loudness equalization described in any of the embodiments.
In one example of the present invention, when an audio decoder decodes an audio signal, a receiving end of the audio decoder performs loudness equalization processing on the audio signal.
In this example, the loudness equalization process of the audio decoder is controlled outside the audio decoder, including selection of a loudness equalization mode by a button; the selection of the loudness equalization adjustment range is achieved by an external input device, such as a numeric keypad.
In one embodiment of the present invention, the bluetooth device of the present invention comprises an audio decoder, wherein the audio decoder is operative to perform the audio decoder-based loudness equalization method described in any of the embodiments
In one example of the present invention, the bluetooth devices of the present invention include, but are not limited to, BR/EDR bluetooth devices and BLE bluetooth low energy devices.
According to the loudness equalization method based on the audio decoder, disclosed by the invention, on a platform based on the Bluetooth technology and the LC3 decoding technology, when different audio/audio programs are switched, a user can experience relatively consistent loudness, frequent manual adjustment of the user is avoided, and the user experience is enhanced; the technology is exemplified by a television, a set top box and a Bluetooth sound box, and can also be applied to other platforms based on the Bluetooth technology, such as a mobile phone or a music player, a Bluetooth headset or a Bluetooth sound box; the technique is exemplified by an LC3 decoder, but can also be applied to platforms using other decoders, such as AAC audio decoder, SBC audio decoder, etc.; this technique is illustrated by a single channel, but in practice, the present invention can also be used in two or more channels. The loudness equalization method based on the audio decoder can be applied to a Bluetooth transmitting terminal, and adopts multiple mode selections of a fixed loudness output mode and an average loudness output mode, so that a subsequent user can change loudness and reset the system according to the self condition, the loudness consistency is ensured when audio and video programs are switched, frequent loudness adjustment is avoided, and the user experience is greatly improved.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of a unit is merely a logical division, and an actual implementation may have another division, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
The above description is only an embodiment of the present invention, and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (11)
1. A method for loudness equalization in an audio decoder, comprising:
calculating a first effective loudness step: measuring the loudness of a first audio decoding signal, and calculating and storing the first effective loudness according to the effective loudness measurement value and the effective measurement times of the first audio decoding signal;
and (3) loudness statistics step: measuring a first loudness of a second audio decoding signal when the number of buffering frames of the second audio decoding signal is greater than or equal to a loudness calculation length, and measuring a second loudness of the second audio decoding signal when the number of buffering frames of the second audio decoding signal is less than the loudness calculation length and the loudness adjustment is performed on the second audio decoding signal, wherein a measurement time interval of the first loudness is greater than a measurement time interval of the second loudness;
a loudness judging step: taking the measured output value of the first loudness or the second loudness of the second audio decoding signal as a third loudness of the second audio decoding signal, starting loudness adjustment when the third loudness exceeds a first range of the first effective loudness, turning down the loudness of the second audio decoding signal when the third loudness is greater than an upper limit of a second range of the first effective loudness, turning up the loudness of the second audio decoding signal when the third loudness is less than a lower limit of the second range of the first effective loudness, and ending loudness adjustment when the third loudness is greater than or equal to a lower limit of the second range and less than or equal to an upper limit of the second range; and
an updated audio decoding step: comprising a loudness equalization process on the second audio decoded signal, wherein the loudness equalization process comprises:
calculating corresponding loudness variation gain according to the loudness adjustment amplitude;
adjusting the loudness of the second audio decoded signal according to the loudness variation gain.
2. The audio decoder based loudness equalization method of claim 1, where the adjusting the loudness of the second audio decoded signal according to the loudness variation gain comprises:
obtaining a frame loudness variation gain of the second audio decoding signal according to the loudness variation gain and the frame length mapping of the second audio decoding signal;
amplifying or reducing the first loudness equalization factor according to the loudness variation gain of the frame to obtain a second loudness equalization factor;
and adjusting the loudness of one frame of audio coding data of the second audio decoding signal according to the second loudness equalization factor.
3. The audio decoder based loudness equalization method of claim 1, where the first range upper bound is a sum of the first effective loudness and the first loudness threshold, the first range lower bound is a difference of the first effective loudness and the first loudness threshold, the second range upper bound is a sum of the first effective loudness and the second loudness threshold, the second range lower bound is a difference of the first effective loudness and the second loudness threshold, the first loudness threshold is greater than the second loudness threshold.
4. The audio decoder based loudness equalization method of claim 1 where a measurement interval for the first loudness is greater than a measurement interval for the second loudness.
5. The audio decoder based loudness equalization method of claim 1 further comprising:
and an initialization step, wherein the number of times of measurement of the effective loudness is set to 0, the first loudness equalization factor is set to 1, the loudness threshold value is initialized to the first loudness threshold value, and the loudness equalization state value is set to 0, which indicates that the loudness equalization step is not executed.
6. The audio decoder based loudness equalization method of claim 1, where in the loudness equalization step, the loudness adjustment magnitude of the second audio decoded signal is controlled to avoid excessive loudness adjustment of the second audio decoded signal, resulting in overflow.
7. The audio decoder based loudness equalization method of claim 1, where the loudness statistics step is not performed when the audio-video system is in a time of loudness ramp-up or loudness ramp-down during power-up, power-down, or audio switching.
8. The audio decoder based loudness equalization method of claim 1 where the calculating first effective loudness step is not performed when the first effective loudness is set to a fixed value.
9. The audio decoder based loudness equalization method of claim 1, wherein during the loudness equalization adjustment of the second audio decoded signal, the effective value and the effective measurement times of the third loudness of the second audio decoded signal are counted, an average value is calculated to obtain a second effective loudness of the second audio decoded signal, and after the audio decoder finishes decoding, the second effective loudness is stored and replaces the first effective loudness.
10. Audio decoder, characterized in that the audio decoder is operative to perform the audio decoder based loudness equalization method according to any of the claims 1-9.
11. A bluetooth device comprising a BR/EDR bluetooth device or a bluetooth low energy device, comprising:
audio decoder operative to perform the audio decoder based loudness equalization method of any of claims 1-9.
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