HK40115800A - Efficient drc profile transmission - Google Patents

Description

High-efficiency DRC configuration file transfer

This application is a divisional application of patent application No. 202110527052.4, filed on September 29, 2015, entitled "Efficient DRC Configuration File Transmission", which is a divisional application of patent application No. 201580053702.9, filed on September 29, 2015, entitled "Efficient DRC Configuration File Transmission".

Cross-references to related applications

This application claims priority to U.S. Provisional Patent Application No. 62/058,228, filed October 1, 2014, which is incorporated herein by reference in its entirety.

Technical Field

This article relates to audio signal processing. In particular, this article relates to a method and corresponding system for transmitting Dynamic Range Control (DRC) profiles in a bandwidth-efficient manner.

Background Technology

The increasing prevalence of media consumer devices presents both new opportunities and challenges for creators and distributors of media content played back on these devices, as well as for designers and manufacturers of these devices. Many consumer devices are capable of playing back a wide range of media content types and formats, including those typically associated with high-quality, wide-bandwidth, and wide dynamic range audio content used in HDTV, Blu-ray, or DVD. Media processing devices can be used to play back this type of audio content on their own internal acoustic transducers or on external transducers such as headphones or high-quality home theater systems; however, all these playback systems and environments place significantly different demands on the dynamic range of the audio signal due to variations in ambient noise levels or the limited ability of the playback system to reproduce the required sound pressure level without distortion. Environmentally-constrained dynamic range is a method for delivering high quality and high intelligibility across a wide range of rendering devices with varying rendering capabilities and listening environments (i.e., across a wide range of rendering modes).

This paper addresses the following technical problem: providing media content creators and distributors with a bandwidth-efficient means to reproduce audio signals with high quality and intelligibility on a wide range of different rendering devices with varying rendering capabilities.

Summary of the Invention

According to one aspect, a method for generating an encoded audio signal is described. The encoded audio signal includes a frame sequence. The encoded audio signal indicates multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. The method includes inserting different subsets of the multiple DRC profiles into different frames of the frame sequence, such that two or more frames of the frame sequence collectively include the multiple DRC profiles.

According to a further aspect, a method for decoding an encoded audio signal is described. The encoded audio signal includes a frame sequence. Furthermore, the encoded audio signal indicates multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. Different subsets of the multiple DRC profiles are included in different frames of the frame sequence, such that two or more frames in the frame sequence collectively include the multiple DRC profiles. The method includes determining a first rendering mode from the multiple different rendering modes, and determining one or more DRC profiles from the subset of DRC profiles included within the current frame of the frame sequence. Furthermore, the method includes determining whether at least one of the one or more DRC profiles is suitable for the first rendering mode. Additionally, if none of the one or more DRC profiles are suitable for the first rendering mode, then a default DRC profile is selected as the current DRC profile; wherein the definition data of the default DRC profile is known at the decoder used to decode the encoded audio signal. Furthermore, the method includes decoding the current frame using the current DRC profile.

According to a further aspect, a bitstream comprising an encoded audio signal is described. The encoded audio signal comprises a frame sequence. The encoded audio signal indicates multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. Different subsets of the multiple DRC profiles are included in different frames of the frame sequence such that two or more frames in the frame sequence collectively include the multiple DRC profiles.

According to another aspect, an encoder for generating encoded audio signals is described. The encoded audio signals comprise a sequence of frames. The encoded audio signals indicate multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. The encoder is configured to insert different subsets of the multiple DRC profiles into different frames of the frame sequence, such that two or more frames in the frame sequence collectively include the multiple DRC profiles.

According to a further aspect, a decoder for decoding encoded audio signals is described. The encoded audio signals include a sequence of frames. The encoded audio signals indicate multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. Different subsets of the multiple DRC profiles are included in different frames of the frame sequence such that two or more frames of the frame sequence jointly include the multiple DRC profiles. The decoder is configured to: determine a first rendering mode from the multiple different rendering modes; determine one or more DRC profiles from the subset of DRC profiles included within the current frame of the frame sequence; determine whether at least one of the one or more DRC profiles is suitable for the first rendering mode; if none of the one or more DRC profiles are suitable for the first rendering mode, select a default DRC profile as the current DRC profile; wherein the definition data of the default DRC profile is known at the decoder; and decode the current frame using the current DRC profile.

According to a further aspect, a software program is described. The software program is adaptable to execute on a processor and, when implemented on a processor, to perform the method steps outlined herein.

According to another aspect, a storage medium is described. The storage medium may include a software program adapted to execute on a processor and, when implemented on a processor, to perform the method steps outlined herein.

According to a further aspect, a computer program product is described. The computer program product may include executable instructions for performing the method steps outlined herein when executed on a computer.

It should be noted that the methods and systems, including their preferred embodiments, as outlined in this patent application can be used alone or in combination with other methods and systems disclosed herein. Furthermore, all aspects of the methods and systems outlined in this patent application can be combined arbitrarily. In particular, the features of the claims can be combined with each other in any manner.

Attached Figure Description

The invention will now be described by way of example with reference to the accompanying drawings, wherein...

Figures 1 and 2 illustrate an example audio decoder and an example audio encoder, respectively.

Figures 3 and 4 illustrate example dynamic range compression curves;

Figure 5 illustrates an example frame sequence; and

Figure 6 shows a flowchart of an example method for selecting a DRC profile.

Detailed Implementation

As indicated above, this document addresses the technical challenges of enabling designers and/or distributors of audio content to control the quality and intelligibility of audio content for different types of rendering modes. An example rendering mode is the home theater rendering mode, in which audio content is played back using transducers that typically allow a very wide dynamic range in a quiet environment. Another example rendering mode is the flat panel mode, in which audio content is played back using transducers such as those found in televisions, which typically allow a reduced dynamic range compared to home theater. A further example rendering mode is the portable speaker mode, in which audio content is played back using the amplifier of a portable electronic device (such as a smartphone). The dynamic range of this rendering mode is typically smaller than the rendering modes mentioned above, and the environment is often noisy. Another example rendering mode is the portable headphone mode, in which audio content is played back using headphones combined with a portable electronic device. The dynamic range is limited, but generally higher than that provided by the amplifier of the portable electronic device.

To allow for high quality and intelligibility across different rendering modes, different DRC (Dynamic Range Control) profiles for each rendering mode can be provided along with audio content. The audio content can be transmitted in a frame sequence. The frame sequence can include I-frames (i.e., independent frames), which can be decoded independently of previous or subsequent frames. Furthermore, the frame sequence can include other types of frames (e.g., P-frames and/or B-frames) that typically exhibit correlation with the preceding and/or following frames. At least some frames in the frame sequence can include multiple different DRC profiles for multiple different rendering modes. Specifically, the I-frames of the frame sequence can include the multiple DRC profiles.

By inserting multiple different DRC profiles into the audio frame sequence, the audio decoder is able to select the appropriate DRC profile for a specific rendering mode. As a result, the rendered audio signal can be ensured to have high quality (especially without clipping or distortion introduced by the transducer) and high intelligibility.

Below, various aspects of dynamic range control are described. Without customized dynamic range control, input audio information (e.g., PCM samples, time-frequency samples in a QMF matrix, etc.) is typically reproduced at the playback device at a loudness level unsuitable for the specific playback environment of the playback device (i.e., including the device's physical and/or mechanical playback limitations), because the specific playback environment of the playback device may differ from the target playback environment for which the encoded audio content has been encoded at the encoding device.

The techniques described in this article can be used to support dynamic range control of a variety of audio content tailored to any playback environment in a variety of playback environments, while maintaining the perceptual quality of the audio content and the artist's intention to adapt the content to different listening environments.

Dynamic range control (DRC) refers to a time-varying, level-dependent audio processing operation that alters (e.g., compresses, cuts, expands, boosts) a signal to convert the input dynamic range of loudness levels in audio content into an output dynamic range different from the input dynamic range. For example, in a DRC scenario, a soft sound might be mapped (e.g., boosted) to a higher loudness level, while a loud sound might be mapped (e.g., cut) to a lower loudness level. As a result, in the loudness domain, the output range of loudness levels becomes smaller than the input range of loudness levels in this example. In some embodiments, however, DRC can be reversible, allowing the original range to be restored. For example, an expansion operation can be performed to restore the original range, whereby each unique original loudness level is mapped to a unique output loudness level, and so on, provided that the mapped loudness level from the original loudness level in the output dynamic range is at or below a limiting level.

As described in this article, DRC technology can be used to provide a better listening experience in certain playback environments or situations. For example, a soft sound in a noisy environment may be masked by noise that makes the soft sound inaudible. Conversely, a loud sound may be undesirable in some situations, such as disturbing neighbors (e.g., in "late-night" listening mode). Many devices with amplifiers that typically have small shape factors cannot reproduce high output levels of sound, or sound without perceptible distortion. In some cases, lower signal levels may be reproduced below the human hearing threshold. DRC technology can perform a mapping from input loudness level to output loudness level based on the DRC gain (e.g., scaling factor, boost ratio, clipping ratio, etc.) found through a dynamic range compression curve.

Dynamic range compression (DLL) refers to a function (e.g., lookup table, curve, multi-segment line, etc.) that maps individual input loudness levels (e.g., input loudness levels of sounds other than dialogue, etc.) determined from individual audio data frames to corresponding output loudness levels. The result is mapped to individual gains or gains used for dynamic range control to transform the input loudness levels into corresponding output loudness levels. Each gain is an indication of the amount of gain applied to the signal to map the corresponding single input loudness level to the desired output loudness level. The output loudness level after applying the gains represents the target loudness level of the audio content in each audio data frame within a specific playback environment.

In addition to specifying the mapping between gain and loudness levels, the dynamic range compression curve may also include, or may further include, specific release times and attack times for applying a specific gain. Attack time refers to the increase in signal energy (or loudness) between consecutive time samples, while release time refers to the decrease in energy (or loudness) between consecutive time samples. Attack time (e.g., 10 ms, 20 ms, etc.) is the time constant used to smooth the DRC gain when the corresponding signal is in attack mode. Release time (e.g., 80 ms, 100 ms, etc.) is the time constant used to smooth the DRC gain when the corresponding signal is in attack mode. In some embodiments, additionally, optionally, or alternatively, the time constant is used to smooth the signal energy (or loudness) before determining the DRC gain.

Different dynamic range compression curves can correspond to different playback environments (i.e., different rendering modes). For example, the dynamic range compression curve for a playback environment of a flat-panel TV can be different from the dynamic range compression curve for a playback environment of a portable device. A playback device can have two or more playback environments. For example, the first dynamic range compression curve for a first playback environment of a portable device with speakers can be different from the second dynamic range compression curve for a second playback environment of the same portable device with headsets.

Figure 1 shows a block diagram of example components of an audio decoder 100. The audio decoder 100 includes a data extractor 104, a dynamic range controller 106, and an audio renderer 108. The data extractor 104 is configured to receive an encoded input signal 102. The encoded input signal 102, as described herein, can be a bitstream containing encoded (e.g., compressed, etc.) input audio data frames (especially a sequence of audio frames) and possibly metadata. This bitstream can be an AC-4 bitstream. The data extractor 104 is configured to extract/decode the input audio data frames and metadata from the encoded input signal 102. Each input audio data frame includes multiple encoded audio data blocks, each representing multiple audio samples. Each frame represents a (e.g., constant) time interval comprising a certain number of audio samples. The frame size can vary with the sampling rate and the encoded data rate. An audio sample is a quantized audio data element (e.g., input PCM sample, input time-frequency sample in a QMF matrix, etc.) representing one, two, or more (audio) bands or frequency ranges. Quantized audio data elements in an input audio data frame can represent sound pressure waves in the digital (quantization) domain. Quantized audio data elements can cover a finite range of loudness levels that reach or fall below the maximum possible value (e.g., limiting level, maximum loudness level, etc.).

Metadata can be used by the audio decoder 100 to process the input audio data frames. Metadata may include various operational parameters related to one or more operations to be performed by the decoder 100, one or more dynamic range compression curves (i.e., one or more DRC profiles), normalization parameters related to the dialogue loudness level represented in the input audio data frames, etc. Dialogue loudness level can refer to the dialogue loudness in the entire program (e.g., a movie, TV program, radio broadcast, etc.), a portion of the program, dialogue in the program, program loudness, average dialogue loudness, etc. (e.g., psychoacoustic, perceptual, etc.).

The operation and function of decoder 100 or some or all of its modules (e.g., data extractor 104, dynamic range controller 106, etc.) can be modified in response to metadata extracted from encoded input signal 102. For example, metadata—including but not limited to dynamic range compression curves, dialogue loudness levels, etc.—can be used by decoder 100 to generate audio data elements in the digital domain (e.g., output PCM samples, output time-frequency samples in a QMF matrix, etc.). The output data elements can then be used to drive audio channels or speakers to achieve a specified loudness or reference reproduction level during playback in a particular playback environment.

The dynamic range controller 106 can be configured to receive some or all of the audio data elements in the input audio data frame, as well as metadata, and to perform audio processing operations (e.g., dynamic range control operations, gain smoothing operations, gain limiting operations, etc.) on the audio data elements in the input audio data frame, at least in part based on the metadata extracted from the encoded audio signal 102.

Specifically, the dynamic range controller 106 may include a selector 110, a loudness calculator 112, and/or a DRC gain unit 114. The selector 110 may be configured to determine a speaker configuration (e.g., home theater mode, flat panel mode, portable device with speaker mode, portable device with headphone mode, 5.1 speaker configuration mode, 7.1 speaker configuration mode, etc.) associated with a specific playback environment at the decoder 100. The speaker configuration may also be referred to as a rendering mode. Furthermore, the selector 110 may be configured to select a specific dynamic range compression curve (i.e., a DRC profile) from dynamic range compression curves extracted from the metadata of the encoded input signal 102 (i.e., from multiple DRC profiles).

Loudness calculator 112 can be configured to calculate one or more types of loudness levels represented by audio data elements in an input audio data frame. Examples of loudness level types include, but are not limited to, any of the following: loudness levels in various frequency bands of various channels over various time intervals; wideband (or broadband) loudness levels over a wide (or broad) frequency range in various channels; loudness levels determined from or smoothed over audio data blocks or frames; loudness levels determined from or smoothed over more than one audio data block or frame; loudness levels smoothed over one or more time intervals; etc. Zero or more of these loudness levels can be changed for the purpose of dynamic range control of decoder 100.

To determine loudness levels, loudness calculator 112 can determine one or more time-dependent physical acoustic properties represented by audio data elements in an input audio data frame, such as spatial and/or local pressure levels at specific audio frequencies. Loudness calculator 112 can use these one or more time-varying physical acoustic properties to derive one or more types of loudness levels based on one or more psychoacoustic functions modeling human loudness perception. The psychoacoustic function can be a nonlinear function constructed based on a model of the human auditory system, which converts/maps a specific spatial pressure level at a specific audio frequency to a specific loudness for those specific audio frequencies.

Loudness levels at multiple (audio) frequencies or frequency bands (e.g., broadband, wideband, etc.) can be obtained by integrating specific loudness levels at said multiple (audio) frequencies or frequency bands. A time-averaged, smoothed, etc., loudness level over one or more time intervals (e.g., longer than the time interval represented by audio data elements in an audio data block or frame) can be obtained by using one or more smoothing filters implemented as part of audio processing operations in decoder 100. Another example method for determining (broadband) loudness levels is specified in ITU-R BS.1770. The method specified in ITU-R BS.1770 applies a time-domain filter to the time-domain input audio signal and then calculates the RMS (root mean square) level on each channel of the input audio signal, prior to integration on the channels and gating the resulting loudness levels.

A specific loudness level for different frequency bands can be calculated for each audio data block with a certain number of samples (e.g., 256, etc.). In integrating specific loudness levels into a wideband (or broadband) loudness level, a pre-filter can be used to apply frequency weighting (e.g., similar to IECB-weighting, etc.) to the specific loudness level. The summation of wide loudness levels on two or more channels (e.g., left front, right front, center, left surround, right surround, etc.) can be performed to provide the overall loudness level of said two or more channels.

The overall loudness level can refer to the broadband (wideband) loudness level in a single channel (e.g., center, etc.) of a speaker configuration. The overall loudness level can also refer to the broadband (or wideband) loudness level across multiple channels. These multiple channels can be all channels in the speaker configuration (i.e., those used for rendering modes). Additionally, optionally, or alternatively, the multiple channels may include subsets of channels in the speaker configuration (e.g., subsets including left front, right front, and low-frequency effects (LFE); subsets including left surround and right surround; and a subset including the center, etc.).

Loudness levels (e.g., broadband, wideband, overall, specific, etc.) can be used as input to find the corresponding (e.g., static, pre-smoothed, pre-limited, etc.) DRC gain from a selected dynamic range compression curve. The loudness level to be used as input for finding the DRC gain can first be adjusted or normalized relative to the dialogue loudness level derived from metadata extracted from the encoded audio signal 102 and/or relative to the output reference level of the rendering mode. Before a specific spatial pressure level represented in a portion of the audio content in the encoded audio signal 102 is converted or mapped to a specific loudness level in that portion of the audio content in the encoded audio signal 102, adjustments and normalization related to adjusting the dialogue loudness level/output reference level can be performed on that portion of the audio content in the encoded audio signal 102 in a non-loudness domain (e.g., SPL domain, etc.).

DRC gain unit 114 can be configured with a DRC algorithm that generates a gain (e.g., a gain for dynamic range control, gain limiting, gain smoothing, etc.) and applies the gain to one or more types of loudness levels represented by audio data elements in the input audio data frame to achieve a target loudness level for a particular playback environment. The application of the gain (e.g., DRC gain, etc.) as described herein can occur in the loudness domain. For example, the gain can be generated based on loudness calculations (which may be in the Son, or simply, for example, an unconverted SPL value compensated for the dialogue loudness level), smoothed, and applied directly to the input signal. Techniques as described herein can apply the gain to the signal in the loudness domain, then convert the signal back from the loudness domain to the (linear) SPL domain, and calculate the corresponding gain to be applied to the signal by evaluating the signal in the loudness domain before and after the gain is applied. The ratio (or the difference when expressed in logarithmic dB) is then used to determine the corresponding gain for the signal.

The DRC algorithm can operate using multiple DRC parameters. These parameters include a dialogue loudness level, which has been calculated by the upstream encoder 150 (as described in the context of Figure 2) and embedded into the encoded audio signal 102, and can be obtained by the decoder 100 from metadata in the encoded audio signal 102. The dialogue loudness level from the upstream encoder 150 indicates the average dialogue loudness level (e.g., per program, energy relative to a 1kHz sine wave on full scale, energy relative to a reference rectangular wave, etc.). The dialogue loudness level extracted from the encoded audio signal 102 can be used to reduce loudness level differences between programs. At the decoder 100, within the same specific playback environment, the reference dialogue loudness level can be set to the same value across different programs. Based on the dialogue loudness level from metadata, the DRC gain unit 114 can apply dialogue loudness-related gain to each audio data block in the program, so that the averaged output dialogue loudness level (or output reference level) across multiple audio data blocks of the program is increased/decreased to the program's reference dialogue loudness level (e.g., pre-configured, system default, user-configurable, profile-dependent, etc.). The dialogue loudness level can also be used to calibrate the DRC algorithm; in particular, the zero band of the DRC algorithm can be adjusted to the dialogue loudness level. Alternatively, the desired output reference level can be used to calibrate the DRC algorithm when it is applied to a signal that has already been given gain, so that the dialogue loudness level becomes equal to the desired output reference level. If voice gating has been used to determine the dialogue norm parameter, the dialogue loudness level can correspond to the so-called dialogue norm parameter. In some embodiments, the dialogue loudness level corresponds to a dialogue norm parameter determined not by voice gating, but by gating based on a loudness level threshold.

DRC gains can be used to address loudness level differences within a program by boosting or cutting off signal portions in soft and/or loud sounds according to a selected dynamic range compression curve. One or more of these DRC gains can be calculated/determined by a DRC algorithm based on a selected dynamic range compression curve and a defined (e.g., wideband, broadband, overall, specific, etc.) loudness level from one or more corresponding audio data blocks, audio data frames, etc.

The loudness level used to determine the DRC gain by finding a selected dynamic range compression curve (e.g., static, pre-smoothed, pre-gain limited, etc.) can be calculated in short intervals (e.g., approximately 5.3 milliseconds, etc.). The integration time of the human auditory system (e.g., approximately 200 milliseconds, etc.) can be much longer. The DRC gain obtained from the selected dynamic range compression curve can be smoothed using a time constant that takes into account the long integration time of the human auditory system. To achieve a rapid rate of change (increase or decrease) in the loudness level, a short time constant can be used to change the loudness level within a short time interval corresponding to the short time constant. Conversely, to achieve a slow rate of change (increase or decrease) in the loudness level, a long time constant can be used to change the loudness level within a long time interval corresponding to the long time constant.

The human auditory system can respond to increasing and decreasing loudness levels with different integration times. Different time constants can be used to smooth the static DRC gain derived from a selected dynamic range compression curve, depending on whether the loudness level is increasing or decreasing. For example, corresponding to the characteristics of the human visual system, increase (loudness level increase) can be smoothed with a relatively short time constant (e.g., increase time, etc.), while release (loudness level decrease) can be smoothed with a relatively long time constant (e.g., release time, etc.).

The DRC gain for a portion of the audio content (e.g., one or more audio data blocks, audio data frames, etc.) can be calculated using the loudness level determined from that portion of the audio content. The loudness level to be used to find in the selected dynamic range compression curve can be adjusted first relative to the dialogue loudness level in the metadata extracted from the encoded audio signal 102 (e.g., in a program where the audio content is part of the dialogue, etc.).

A reference dialogue loudness level/output reference level can be specified or established for a specific playback environment at decoder 100 (e.g., -31 dB _FS in "line" mode, -20 dB _FS in "RF" mode, etc.). Additionally, alternatively, or optionally, in some embodiments, the user may be given control over setting or changing the reference dialogue loudness level at decoder 100.

DRC gain unit 114 can be configured to determine a dialogue loudness-related gain for audio content such that the input dialogue loudness level becomes a reference dialogue loudness level as the output dialogue loudness level.

The audio renderer 108 can be configured to generate channel-specific audio data 116 (e.g., multi-channel, etc.) for a specific speaker configuration after applying a gain determined based on DRC, gain limiting, gain smoothing, etc., to the input audio data extracted from the encoded audio signal 102. The channel-specific audio data 116 can be used to drive speakers, headphones, etc., as indicated in the speaker configuration.

Additionally and/or optionally, decoder 100 may be configured to perform one or more other operations related to processing, rendering, downmixing, resampling, etc., associated with the input audio signal.

The techniques described herein can be used with various speaker configurations corresponding to a wide range of surround sound configurations (e.g., 2.0, 3.0, 4.0, 4.1, 4.1, 5.1, 6.1, 7.1, 7.1, 10.2, 10-60 speaker configurations, 60+ speaker configurations, object signals or combinations of object signals, etc.) and various rendering environment configurations (e.g., cinemas, parks, opera houses, concert halls, bars, homes, auditoriums, etc.).

Figure 2 illustrates an example encoder 150. Encoder 150 may include an audio content interface 152, a dialogue loudness analyzer 154, a DRC reference library 156, and an audio signal encoder 158. Encoder 150 may be part of a broadcasting system, an Internet-based content server, an over-the-air network operator system, a film production system, etc.

The audio content interface 152 can be configured to receive audio content 160 and audio content control input 162, for generating an encoded audio signal 102 based on at least some or all of the audio content 160 and audio content control input 162. For example, the audio content interface 152 can be used to receive audio content 160 and audio content control input 162 from a content creator, content provider, etc.

Audio content 160 may constitute some or all of total media data, including only audio, audiovisual, etc. Audio content 160 may include portions of a program, a program, several programs, one or more commercials, etc.

The dialogue loudness analyzer 154 can be configured to determine/establish one or more dialogue loudness levels for one or more portions of audio content 152 (e.g., one or more programs, one or more commercials, etc.). The audio content can be represented by one or more audio tracks. The dialogue audio content of the audio content can be in a separate audio track, and/or at least a portion of the dialogue audio content of the audio content can be in an audio track that includes non-dialogue audio content.

Audio content control input 162 may include some or all of the following: user control input, control input provided by a system/device outside the encoder 150, control input from the content creator, control input from the content provider, etc. For example, a user (such as a mixing engineer) may provide/specify one or more dynamic range compression curve identifiers; these identifiers may be used to retrieve one or more dynamic range compression curves best suited for the audio content 160 from a database (such as a DRC reference database (156) etc.).

DRC reference library 156 can be configured to store DRC reference parameter sets, etc. The DRC reference parameter set may include definition data for one or more dynamic range compression curves, etc. Encoder 150 can (e.g., concurrently) encode more than one dynamic range compression curve into the encoded audio signal 102. Zero, one, or more dynamic range compression curves can be standard-based, proprietary, custom, decoder-modifiable, etc. For example, the dynamic range compression curves of Figures 3 and 4 can (e.g., concurrently) be encoded into the encoded audio signal 102.

The audio signal encoder 158 can be configured to: receive audio content from the audio content interface 152, receive dialogue loudness levels from the dialogue loudness analyzer 154, retrieve one or more DRC reference parameter sets (i.e., DRC profiles) from the DRC reference library 156, format the audio content into audio data blocks/frames, format dialogue loudness levels, DRC reference parameter sets, etc. into metadata (e.g., metadata containers, metadata fields, metadata structures, etc.), and encode the audio data blocks/frames and metadata into an encoded audio signal 102.

The audio content to be encoded as encoded audio signal 102 as described herein can be received in one or more of various ways (e.g., wirelessly, via a wired connection, via a file, via internet download, etc.) and in one or more of various source audio formats.

The encoded audio signal 102 described herein can be part of a larger media data bitstream (e.g., for audio broadcasting, audio programs, audiovisual programs, audiovisual broadcasting, etc.). The media data bitstream can be accessed from servers, computers, media storage devices, media databases, media files, etc. The media data bitstream can be broadcast, transmitted, or received via one or more wireless or wired network links. The media data bitstream can also be transmitted via an intermediate medium (e.g., one or more of network connections, USB connections, wide area networks, local area networks, wireless connections, optical connections, buses, crossbar connections, serial connections, etc.).

Any of the components described (e.g., Figures 1 and 2) can be implemented as one or more processes and/or one or more IC circuits (e.g., ASIC, FPGA, etc.), and can be implemented in hardware, software, or a combination of hardware and software.

Figures 3 and 4 illustrate example dynamic range compression curves that can be used by the DRC gain unit 104 in decoder 100 to derive DRC gain from the input loudness level. As illustrated, the dynamic range compression curve can be centered on a reference loudness level in the program (e.g., the output reference level) to provide a total gain suitable for a particular playback environment. The following table shows example definition data for dynamic range compression curves (e.g., definition data in the metadata of the encoded audio signal 102) (e.g., including, but not limited to, any of the following: boost ratio, clipping ratio, boost time, release time, etc.). For different playback environments (e.g., at decoder 100), different profiles (e.g., filmstandard, film light, music standard, film light, speech, etc.) can be different:

Table 1

One or more compression curves, described by loudness levels in dB _SPL or dB _FS and gain in dB associated with dB _SPL , can be received, while DRC gain calculations are performed using different loudness representations (e.g., Sone) that have a non-linear relationship with the dB _SPL loudness level. The compression curves used in the DRC gain calculations can then be converted to be described using different loudness representations (e.g., Sone).

Figure 5 illustrates an example coded audio signal 102 comprising a sequence of frames (numbered n+1 to n+30, where n is an integer). In the illustrated example, every 5th frame is an I-frame. In the illustrated example, the I-frame (n+1) comprises multiple DRC profiles (identified as AVRs (audio/video receivers) for home theaters, tablets, portable HP (headphones), and portable SP (speakers). Each DRC profile includes a dynamic range compression curve as shown in Figures 3 and 4.

The multiple DRC profiles can be repeatedly inserted into the I-frames of the frame sequence. This allows the decoder 100 to determine the appropriate DRC profile for the encoded audio signal 102 and the current rendering mode when the encoded audio signal 102 is initiated, when it is tuned to the running audio program, and/or after a subsequent splicing point. On the other hand, the repeated transmission of the entire set of DRC profiles results in relatively high bitstream overhead. In view of this, a subset of varying DRC profiles is proposed to be transmitted within the I-frames of the encoded audio signal 102.

Figure 5 illustrates an example of inserting DRC profiles into a frame sequence. In the illustrated example, only a single DRC profile from the complete set of DRC profiles is inserted into an I-frame. The DRC profiles inserted into the I-frames change between I-frames, and as a result, after N I-frames (N=4 in the illustrated example), decoder 100 has received the complete set of N DRC profiles. By doing so, the data rate used to transmit the complete set of DRC profiles can be reduced, while ensuring that decoder 100 receives the complete set of DRC profiles within a reasonable amount of time.

Figures 6a and 6b illustrate flowcharts of an example method 600 for determining a DRC profile for decoding frames of encoded audio signal 102. Method 600 can be performed by decoder 100 (specifically by selector 110). When receiving encoded audio signal 102 begins, the DRC profile used by decoder 100 can be initialized. The DRC profile used for decoding the current frame of encoded audio signal 102 can be referred to as the current DRC profile. Therefore, the current DRC profile can be initialized upon startup. In particular, the default DRC profile (which is available at decoder 100) can be set to the current DRC profile used for rendering the current frame (method step 601). Thus, the variable “profile” can be set to the default DRC profile (profile = Default DRC Profile). Furthermore, decoder 100 can keep track of previously used profiles. Previously used profiles can be set to undefined (prev_profile = undefined).

Method 600 may further include step 602 of obtaining a new frame (i.e., the current frame) to be decoded from the encoded audio signal 102. In step 603, it is verified whether the new frame is an I-frame that may include a DRC profile. If the new frame is not an I-frame, method 600 proceeds to step 604 and processes the new frame using the current DRC profile. Furthermore, in method step 605, the previously used profile is set as the current DRC profile (prev_profile = profile).

If the new frame is an I-frame, then in method step 606, it can be checked whether the I-frame includes DRC data. For example, the metadata of the I-frame may include a flag indicating whether the I-frame includes DRC data. If the DRC data is not present, method 300 may proceed to steps 604 and 605. Otherwise, the method may proceed to method step 607.

In method step 607, it can be verified whether the new frame is the first frame of the encoded audio signal 102 to be decoded. As can be seen from the flowcharts in Figures 6a and 6b, this can be verified by checking the `prev_profile` variable. If the `prev_profile` variable is undefined, then the new frame is the first frame to be decoded. If the new frame is the first frame to be decoded, then decoder 100 can use a predefined DRC profile other than the default DRC profile. For this purpose, the metadata of the new frame can include an identifier (ID) for such a predefined DRC profile. Such a predefined DRC profile can be stored in a database at decoder 100. The use of a predefined DRC profile provides a bit-rate efficient means of signaling decoder 100 to use a DRC profile, since only the ID of the predefined profile needs to be transmitted (method step 608). A predefined DRC profile signaled using an ID can also be referred to as an implicit DRC profile.

It should be noted that in some cases, it may be beneficial to use only a predefined DRC profile in addition to the default DRC profile. In such cases, decoder 100 can be configured to set the profile variable to the predefined (i.e., implicit) DRC profile without receiving any IDs within the metadata of new frames.

Method 600 may further include verifying whether the metadata of the new frame includes one or more explicit DRC profiles (step 609). An explicit DRC profile may include an ID used to identify the explicit DRC profile. Furthermore, an explicit DRC profile typically includes definition data for a dynamic range compression curve, as shown in Figures 3 and 4. The dynamic range compression curve may be defined as a piecewise linear function. Additionally, the explicit DRC profile may indicate the range of output reference levels (ORL) to which the explicit DRC profile applies. For example, a default DRC profile and/or a predefined (implicit) DRC profile may apply to output reference levels ranging from -31 dB FS to 0 dB FS.

The rendering device's ORL (Organizational Range) indicates its dynamic range capability. Generally, dynamic range capability decreases as ORL increases. With a high ORL, a highly compressed profile should be used to render the audio signal in an intelligible manner without clipping. Conversely, with a low ORL, compression can be reduced to render the audio signal with a high dynamic range. Because of the high dynamic range capability of the rendering device, the intelligibility of the audio signal can still be guaranteed.

If the metadata of the new frame includes at least one explicit DRC profile, the profile data of the first DRC profile is read (step 610). Furthermore, it is verified that the ORL range of the first DRC profile is applicable to the currently used rendering device (step 611). If not, method 600 continues to search for another explicit DRC profile within the metadata of the new frame. Alternatively, if the explicit DRC profile is applicable to the rendering device, it can be set as the current DRC profile to be used for processing the new frame (step 614).

Method 600 may further include verifying whether the headphone rendering mode is used and whether the explicit DRC profile is applicable to the headphone rendering mode (step 612). Additionally, method 600 may include verifying whether the explicit DRC profile is a newer profile compared to a previously used profile (step 613). For this purpose, the ID of the explicit DRC profile can be compared with the ID of the currently used profile. By doing so, it can be ensured that the decoder 100 always uses the most recent DRC profile.

Using method 600, it can be ensured that even if decoder 100 has not yet received a DRC profile for the current rendering mode (i.e., for the current rendering device), decoder 100 can always recognize the DRC profile used to render the frames of the encoded audio signal 102. Furthermore, it ensures that decoder 100 applies the DRC profile for the current rendering mode as soon as it receives the corresponding DRC profile.

Therefore, a method 600 for decoding encoded audio signal 102 is described. Encoded audio signal 102 includes a sequence of frames. Furthermore, encoded audio signal 102 indicates multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. Examples for different rendering modes (or different reproduction environments) include a first DRC profile used in a home theater rendering mode; a second DRC profile used in a tablet rendering mode; a third DRC profile used in a portable device loudspeaker rendering mode; and/or a fourth DRC profile used in a headphone rendering mode. The DRC profile defines specific DRC behavior. DRC behavior can be described by a compression curve (and time constant) and/or by DRC gain. The DRC gain can be a time-isolated gain that can be applied to the encoded audio signal 102 to deploy DRC. The compression curve may be accompanied by a time constant; together, they configure the DRC algorithm. DRC typically reduces the volume of loud sounds and amplifies quiet sounds, thereby compressing the dynamic range of the audio signal to improve the experience in less-than-ideal reproduction environments.

A frame sequence typically comprises multiple consecutive frames that form an audio signal. An audio program (e.g., broadcast TV or radio program) may include multiple audio signals joined together at splicing points. For example, a main audio program may be interrupted by repeating commercial breaks. A frame sequence may correspond to the entire audio program. Alternatively, a frame sequence may correspond to one of the multiple audio signals that form the entire audio program.

Different subsets of the multiple DRC profiles can be included in different frames of the frame sequence so that two or more frames of the frame sequence jointly include the multiple DRC profiles. As indicated above, the distribution of DRC profiles across multiple frames of the frame sequence results in a reduction in bitstream overhead for signaling the multiple DRC profiles.

Method 600 may include determining a first rendering mode from a plurality of different rendering modes. Specifically, it may be determined which rendering mode is used to render the encoded audio signal 102. Furthermore, method 600 may include determining 609, 610 one or more DRC profiles from a plurality of DRC profiles included within the current frame of the frame sequence. In other words, it may be determined one or more DRC profiles from a subset of DRC profiles included within the current frame. Additionally, it may be determined 611 whether at least one of the one or more DRC profiles is suitable for the first rendering mode. Determining 611 whether at least one of the one or more DRC profiles is suitable for the first rendering mode may include: determining a first output reference level for the first rendering mode, determining a range of output reference levels to which the DRC profiles in the one or more DRC profiles are applicable, and determining whether the first output reference level falls within the range of output reference levels.

Method 600 may further include: if none of the one or more DRC profiles are suitable for the first rendering mode, then selecting a default DRC profile 604 as the current DRC profile. The definition data of the default DRC profile is generally known at the decoder 100 used to decode the encoded audio signal 102. Additionally, method 600 may include decoding (and/or rendering) the current frame using the current DRC profile. Therefore, it can be ensured that decoder 100 can use the DRC profile (and dynamic range compression curve) even if decoder 100 has not yet received a DRC profile specific to the encoded audio signal 102.

Alternatively or additionally, method 600 may include: if a first DRC profile among the one or more DRC profiles is determined to be suitable for the first rendering mode, then 604 selecting the first DRC profile as the current DRC profile. As a result, decoder 100 is configured to use the first DRC profile that is optimal for encoding the audio signal 102 and for the first rendering mode as soon as decoder 100 receives the first DRC profile.

Method 600 may further include determining whether the current frame of the frame sequence 603, 606 includes one or more of the plurality of DRC profiles, i.e., whether the current frame includes a subset of DRC profiles. As outlined in the context of Figure 5, a subset of DRC profiles is typically included within an I-frame of the frame sequence. Therefore, determining whether the current frames 603, 606 include one or more of the plurality of DRC profiles or whether the current frame includes a subset of DRC profiles may include determining whether the current frame 603 is an I-frame. As indicated above, an I-frame can be a frame that can be decoded independently of any other frame in the frame sequence. This may be due to the fact that the data included in such an I-frame is transmitted in a manner independent of the data from preceding or subsequent frames. In particular, the encoding of the data included within an I-frame is indistinguishable from the data included in the preceding or following frame.

Furthermore, determining whether the current frames 603 and 606 include one or more of the plurality of DRC profiles, or whether the current frame includes a subset of DRC profiles, may include verifying the DRC profile flags included in the current frame 606. DRC profiles within the bitstream of the encoded audio signal provide a bandwidth-efficient and computationally efficient means of identifying frames carrying DRC profiles.

Method 600 may further include determining whether the current frame indicates an implicit DRC profile among a plurality of implicit DRC profiles. The implicit DRC profile may include a predefined legacy compression curve and time constant that can be used for transcoding to E-AC-3. As indicated above, the definition data of the implicit DRC profile may be known at the decoder 100 used to decode the input audio signal 102. In contrast to the default DRC profile, the implicit DRC profile may be specific to (as specified, for example, in Table 1) different types of audio signals. The current frame of a frame sequence may indicate a specific implicit DRC profile (e.g., by using an identifier, ID). This can provide a bandwidth-efficient means of signaling the appropriate DRC profile for encoding the audio signal 102. If it is determined that the current frame indicates an implicit DRC profile, then implicit DRC profile 608 can be selected as the current DRC profile.

Decoding the current frame may include setting the level of the frame sequence to equal the first output reference level of the first rendering mode. Additionally, decoding the current frame may include modifying the loudness level of the current frame using a dynamic range compression curve specified within the current DRC profile. Modification of the loudness level may be performed as outlined in the context of Figure 1.

Depending on the frame number in the frame sequence, the current DRC profile may correspond to the default DRC profile (which is typically independent of the input audio signal 102), the implicit DRC profile (which can be modified in a limited way to suit the input audio signal 102), or the first explicit DRC profile (which may have been designed for the input audio signal 102 and/or the first rendering mode).

Typically, only a subset of frames includes a DRC profile. Once the current DRC profile has been selected, it can be used to decode frames in the frame sequence that do not include any DRC profile. Furthermore, even when a frame with a DRC profile is received, the current DRC profile can be maintained, provided that no newer DRC profile and/or more relevant to the encoded audio signal 102 is received (wherein, the selected first explicit DRC profile has a higher relevance than the selected implicit DRC profile, which in turn has a higher relevance than the default DRC profile). By doing so, the continuity and optimality of the DRC profiles used can be ensured.

Complementing the method 600 for decoding the encoded audio signal 102, a method for generating or encoding the encoded audio signal 102 is described. The encoded audio signal 102 includes a frame sequence. Furthermore, the encoded audio signal 102 indicates multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes. The method may include inserting different subsets of the multiple DRC profiles into different frames of the frame sequence, such that two or more frames of the frame sequence collectively include the multiple DRC profiles. In other words, a subset of DRC profiles having fewer DRC profiles than the total number of DRC profiles can be provided along with different frames of the frame sequence. By doing so, the overhead of the encoded audio signal 102 can be reduced while providing the complete set of DRC profiles to the corresponding decoder 100. In other words, the advantage of this method is that the encoder 150 has increased freedom in transmitting DRC data. This freedom can be used to reduce the bit rate.

A frame sequence may include I-frame subsequences (e.g., every Xth frame in a frame sequence may be an I-frame). Different subsets of DRC profiles may be inserted into different (e.g., consecutive) I-frames within an I-frame subsequence. To further reduce bandwidth, I-frames may be skipped; that is, some I-frames may not include any DRC profile data.

For example, each subset of DRC profiles may contain only one DRC profile. Specifically, multiple DRC profiles may comprise N DRC profiles, where N is an integer, N>1. The N DRC profiles can be inserted into N distinct frames in a frame sequence. By doing so, the bit rate required to transmit the DRC profiles can be minimized.

The method may further include inserting multiple DRC profiles into the first frame of a frame sequence (e.g., the first frame of a frame sequence of audio signals). As a result, the rendering of the encoded audio signal 102 can begin directly with the correct explicit DRC profile. As indicated above, an audio program can be subdivided into multiple sub-audio programs, such as a main audio program interrupted by commercial breaks. It may be advantageous to insert multiple DRC profiles into the first frame of each sub-audio program. In other words, it may be advantageous to insert all multiple DRC profiles directly after one or more splicing points of an audio program comprising multiple sub-audio programs.

Different subsets of multiple DRC profiles can be inserted into different frames of a frame sequence, such that each subsequence of M directly contiguous frames in the frame sequence constitutes the multiple DRC profiles, where M is an integer, M>1. In other words, multiple DRC profiles can be repeatedly transmitted within a block of M frames. As a result, decoder 100 must wait for at most M frames before obtaining the optimal explicit DRC profile for encoding audio signal 102.

The method may further include inserting a flag into frames of a frame sequence, wherein the flag indicates whether the frame includes a DRC profile. Providing such a flag enables the corresponding decoder 100 to efficiently identify frames that include DRC profile data.

A DRC profile of multiple DRC profiles can be an explicit DRC profile that includes (i.e., carries) definition data for defining the dynamic range compression curve. As outlined in this document, the dynamic range compression curve provides a mapping between input loudness and output loudness and/or a gain that will be applied to the audio signal. Specifically, the definition data may include one or more of the following: boost gain, which is used to boost the input loudness; boost gain range, which indicates the range of input loudness to which boost gain applies; zero-band range, which indicates the range of input loudness to which a gain of 0 dB applies; clipping gain, which is used to attenuate the input loudness; clipping gain range, which indicates the range of input loudness to which clipping gain applies; boost gain ratio, which indicates the transition between zero gain and boost gain; and/or clipping gain ratio, which indicates the transition between zero gain and clipping gain.

The method may further include inserting an indication (e.g., an identifier, ID) of an implicit DRC profile, wherein the definition data of the implicit DRC profile is generally known to the decoder 100 encoding the audio signal 102. The indication of the implicit DRC profile can provide a bandwidth-efficient means of signaling changes (in a limited manner) to the DRC profile of the encoded audio signal 102 to accommodate modifications.

As outlined above, frames in a frame sequence typically include audio data and metadata. A subset of the DRC profile is usually inserted as metadata.

A DRC profile can include definition data for defining the range of output reference levels to which the DRC profile applies. The output reference level typically indicates the dynamic range of the rendering mode. Specifically, the dynamic range of a rendering mode can decrease as the output reference level increases, and vice versa. Furthermore, the maximum boost gain and maximum clipping gain of the dynamic range compression curve of the DRC profile can increase as the output reference level increases, and vice versa. Therefore, the output reference level provides an efficient means of selecting an appropriate DRC profile (with an appropriate dynamic range compression curve) for a given rendering mode.

The method may further include generating a bitstream comprising the encoded audio signal 102. This bitstream may be an AC4 bitstream, i.e., it may be compatible with the AC4 bitstream format.

The method may further include inserting explicit DRC gains for encoding audio signal 102 into frames of the frame sequence. Specifically, DRC gains applicable to a particular frame of the frame sequence can be inserted into that particular frame. Therefore, each frame of the frame sequence may include a DRC data component comprising one or more explicit DRC gains to be applied to the corresponding frame. In particular, each frame may include different explicit DRC gains for different rendering modes. For this purpose, DRC algorithms for different rendering modes can be applied within encoder 150, and different DRC gains for different rendering modes can be determined at encoder 150. The different DRC gains can then be explicitly inserted into the frame sequence. As a result, the corresponding decoder 100 directly applies explicit DRC gains without performing a DRC algorithm using dynamic range compression curves.

Therefore, the frame sequence may include or may indicate multiple explicit DRC profiles for signaling dynamic range compression curves for multiple corresponding rendering modes. These multiple DRC profiles may be inserted into some (but not all) of the frames in the frame sequence (e.g., I-frames). Furthermore, the frame sequence may include or may indicate one or more DRC profiles for corresponding one or more rendering modes, wherein the one or more DRC profiles indicate that explicit DRC gains for one or more rendering modes are inserted into the frames of the frame sequence. For example, the one or more DRC profiles for signaling explicit DRC gains may include flags indicating whether explicit DRC gains are included in the frames of the frame sequence. DRC gains may be inserted into each frame of the frame sequence. In particular, each frame may include one or more DRC gains that will be used to decode that frame.

The method may include inserting a DRC profile for explicit DRC gain into a subset of frames in the frame sequence. For example, the DRC profile whose DRC gain is transmitted may indicate DRC configuration data for explicit gain. Specifically, the DRC profile whose DRC gain is transmitted may be included in all subsets of said DRC profiles. The DRC configuration data (e.g., flags) may indicate that the frame sequence includes explicit DRC gain for a specific rendering mode. By doing so, decoder 100 is informed that, for a specific rendering mode, the explicit DRC gain will be directly derived from the frames of the frame sequence.

Therefore, the method may further include determining an explicit DRC gain for encoding the audio signal 102 for a specific rendering mode. Additionally, the method may include inserting explicit DRC gains into frames of a frame sequence. Explicit DRC gains can be inserted into frames in the frame sequence to which the explicit DRC gains are applicable. Furthermore, frames in the frame sequence may include one or more explicit DRC gains required for decoding the frames within a specific rendering mode.

The method may further include inserting a DRC profile indicating DRC configuration data for a specific rendering mode into a subset of frames (e.g., I-frames) in the frame sequence. The DRC configuration data (including, for example, flags) may indicate that, for a specific rendering mode, explicit DRC gain is included in the frames of the frame sequence. Therefore, the decoder 100 can efficiently determine whether to use compression curves from multiple DRC profiles to signal dynamic range compression curves or whether to use explicit DRC gain.

The DRC profile used to signal the dynamic range compression curve, and one or more DRC profiles pointing to the explicit DRC profile, can be included in a special syntax element (referred to as, for example, the DRC profile syntax element) of the I-frame of the frame sequence.

The methods and systems described in this document can be implemented as software, firmware, and/or hardware. Some components can be implemented, for example, as software running on a digital signal processor or microprocessor. Other components can be implemented, for example, as hardware and/or application-specific integrated circuits (ASICs). Signals encountered in the described methods and systems can be stored on a medium such as random access memory or optical storage media. They can be transmitted via a network (such as a radio network, satellite network, wireless network, or wired network (e.g., the Internet)). Typical devices using the methods and systems described in this document are portable electronic devices or other consumer devices for storing and/or rendering audio signals.

Claims (12)

1. A method for decoding an encoded audio signal, wherein the encoded audio signal includes a frame sequence, the frames containing encoded audio data and metadata, the metadata including a plurality of different sets of Dynamic Range Control (DRC) gains, and DRC configuration metadata in one or more frames of the frame sequence, wherein the DRC configuration metadata indicates a plurality of DRC profiles associated with the encoded audio signal, and for each DRC profile, indicates a range of output loudness levels to which the DRC profile is applicable, wherein each set of DRC gains corresponds to one of the plurality of DRC profiles, the method comprising: Set the desired output loudness level for the decoded audio signal; Identify one or more DRC profiles, for which the applicable range of output loudness level includes the desired output loudness level of the decoded audio signal; Select one of the identified DRC profiles; Decode the encoded audio signal; The dynamic range of the decoded audio signal is adjusted by applying the DRC gain corresponding to the selected DRC profile to the decoded audio signal. 2. The method of claim 1, wherein the encoded audio signal further includes an indication of the broadband loudness of the audio signal, and wherein the method further comprises: In response to an indication of the broadband loudness of the audio signal and the desired output loudness level of the decoded audio signal, a loudness-related gain is determined; and The loudness-related gain is applied to the adjusted decoded audio signal to obtain a loudness-adjusted decoded audio signal with the desired output loudness level. 3. A decoder for decoding an encoded audio signal; wherein the encoded audio signal includes a sequence of frames, each frame containing encoded audio data and metadata, the metadata including a plurality of different sets of Dynamic Range Control (DRC) gains, and DRC configuration metadata for one or more frames in the frame sequence, wherein the DRC configuration metadata indicates a plurality of DRC profiles associated with the encoded audio signal, and for each DRC profile, indicates a range of output loudness levels to which the DRC profile is applicable, wherein each set of DRC gains corresponds to one of the plurality of DRC profiles, wherein the decoder includes one or more processors performing the following operations: Set the desired output loudness level for the decoded audio signal; Identify one or more DRC profiles, for which the applicable range of output loudness level includes the desired output loudness level of the decoded audio signal; Select one of the identified DRC profiles; Decode the encoded audio signal; The dynamic range of the decoded audio signal is adjusted by applying the DRC gain corresponding to the selected DRC profile to the decoded audio signal. 4. The decoder of claim 3, wherein the encoded audio signal further includes an indication of the broadband loudness of the audio signal, and wherein the one or more processors further perform the following operations: In response to an indication of the broadband loudness of the audio signal and the desired output loudness level of the decoded audio signal, a loudness-related gain is determined; and The loudness-related gain is applied to the adjusted decoded audio signal to obtain a loudness-adjusted decoded audio signal with the desired output loudness level. 5. A method for generating an encoded audio signal (102); wherein the encoded audio signal (102) comprises a frame sequence; wherein the encoded audio signal (102) indicates multiple different Dynamic Range Control (DRC) profiles for corresponding multiple different rendering modes, the method comprising: A flag is inserted into the frames of the frame sequence, wherein the flag indicates whether the frame includes a DRC profile, wherein the DRC profile includes parameters that define the DRC behavior for encoding audio signals; Insert subsets of different DRC profiles from the plurality of different DRC profiles into different frames of the frame sequence, such that two or more frames in the frame sequence collectively include the plurality of different DRC profiles; and All of the different DRC profiles are inserted into the first frame of the frame sequence. 6. An encoder (150) for generating an encoded audio signal (102); wherein the encoded audio signal (102) comprises a frame sequence; wherein the encoded audio signal (102) indicates multiple different dynamic range control (DRC) profiles for corresponding multiple different rendering modes, wherein the encoder (150) is configured to: A flag is inserted into the frames of the frame sequence, wherein the flag indicates whether the frame includes a DRC profile, wherein the DRC profile includes parameters that define the DRC behavior for encoding audio signals; Insert subsets of different DRC profiles from the plurality of different DRC profiles into different frames of the frame sequence, such that two or more frames in the frame sequence collectively include the plurality of different DRC profiles; and All of the different DRC profiles are inserted into the first frame of the frame sequence. 7. A non-transitory computer-readable storage medium comprising a sequence of instructions, wherein, when executed by an audio signal processing apparatus, the sequence of instructions causes the audio signal processing apparatus to perform the method according to any one of claims 1, 2, and 5. 8. An apparatus for decoding encoded audio signals, comprising: processor, A non-transitory computer-readable storage medium comprising a sequence of instructions, wherein, when executed by the processor, the sequence of instructions causes the processor to perform the method according to claim 1 or 2. 9. An apparatus for generating coded audio signals, comprising: processor, A non-transitory computer-readable storage medium comprising a sequence of instructions, wherein, when executed by the processor, the sequence of instructions causes the processor to perform the method according to claim 5. 10. An apparatus for decoding an encoded audio signal, comprising components for performing the method according to claim 1 or 2. 11. An apparatus for generating an encoded audio signal, comprising components for performing the method according to claim 5. 12. A computer program product comprising instructions adapted to cause a computer to perform the method according to any one of claims 1, 2 or 5 when executed by the computer.