Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
  • G10L19/18—Vocoders using multiple modes
  • G10L19/20—Vocoders using multiple modes using sound class specific coding, hybrid encoders or object based coding
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
  • G10L19/008—Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
  • G10L19/02—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 spectral analysis, e.g. transform vocoders or subband vocoders
  • G10L19/028—Noise substitution, i.e. substituting non-tonal spectral components by noisy source
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
  • G10L19/18—Vocoders using multiple modes
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; 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
  • G10L19/18—Vocoders using multiple modes
  • G10L19/22—Mode decision, i.e. based on audio signal content versus external parameters
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
  • H04S3/008—Systems employing more than two channels, e.g. quadraphonic in which the audio signals are in digital form, i.e. employing more than two discrete digital channels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/03—Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
  • H04S2400/11—Positioning of individual sound objects, e.g. moving airplane, within a sound field

Definitions

• the present invention is related to audio encoding/decoding and, in particular, to spatial audio coding and spatial audio object coding.
• Spatial audio coding tools are well-known in the art and are, for example, standardized in the MPEG-surround standard. Spatial audio coding starts from original input channels such as five or seven channels which are identified by their placement in a reproduction setup, i.e., a left channel, a center channel, a right channel, a left surround channel, a right surround channel and a low frequency enhancement channel.
• a spatial audio encoder typically derives one or more downmix channels from the original channels and, additionally, derives parametric data relating to spatial cues such as interchannel level differences in the channel coherence values, interchannel phase differences, interchannel time differences, etc.
• the one or more downmix channels are transmitted together with the parametric side information indicating the spatial cues to a spatial audio decoder which decodes the downmix channel and the associated parametric data in order to finally obtain output channels which are an approximated version of the original input channels.
• the placement of the channels in the output setup is typically fixed and is, for example, a 5.1 format, a 7.1 format, etc.
• the placement of the audio objects in the reproduction scene is flexible and can be determined by the user by inputting certain rendering information into a spatial audio object coding decoder.
• rendering information i.e., information at which position in the reproduction setup a certain audio object is to be placed typically over time can be transmitted as additional side information or metadata.
• a number of audio objects are encoded by an SAOC encoder which calculates, from the input objects, one or more transport channels by downmixing the objects in accordance with certain downmixing information.
• the SAOC encoder calculates parametric side information representing inter-object cues such as object level differences (OLD), object coherence values, etc.
• the inter object parametric data is calculated for individual time/frequency tiles, i.e., for a certain frame of the audio signal comprising, for example, 1024 or 2048 samples, 24, 32, or 64, etc., frequency bands are considered so that, in the end, parametric data exists for each frame and each frequency band.
• the number of time/frequency tiles is 640.
• an audio encoder of claim 1 an audio decoder of claim 8, a method of audio encoding of claim 22, a method of audio decoding of claim 23 or a computer program of claim 24.
• the present invention is based on the finding that, for an optimum system being flexible on the one hand and providing a good compression efficiency at a good audio quality on the other hand is achieved by combining spatial audio coding, i.e., channel-based audio coding with spatial audio object coding, i.e., object based coding.
• spatial audio coding i.e., channel-based audio coding
• spatial audio object coding i.e., object based coding.
• providing a mixer for mixing the objects and the channels already on the encoder-side provides a good flexibility, particularly for low bit rate applications, since any object transmission can then be unnecessary or the number of objects to be transmitted can be reduced.
• the audio encoder can be controlled in two different modes, i.e., in the mode in which the objects are mixed with the channels before being core-encoded, while in the other mode the object data on the one hand and the channel data on the other hand are directly core-encoded without any mixing in between.
• the present invention already allows to perform a mixing/pre-rendering on the encoder-side, i.e., that some or all audio objects are already mixed with the channels so that the core encoder only encodes channel data and any bits required for transmitting audio object data either in the form of a downmix or in the form of parametric inter object data are not required.
• the user has again high flexibility due to the fact that the same audio decoder allows the operation in two different modes, i.e., the first mode where individual or separate channel and object coding takes place and the decoder has the full flexibility to rendering the objects and mixing with the channel data.
• the decoder is configured to perform a post processing without any intermediate object processing.
• the post processing can also be applied to the data in the other mode, i.e., when the object rendering/mixing takes place on the decoder-side.
• the post-processing may refer to downmixing and binauralizing or any other processing to obtain a final channel scenario such as an intended reproduction layout.
• the present invention provides the user with enough flexibility to react to the low bit rate requirements, i.e., by pre-rendering on the encoder-side so that, for the price of some flexibility, nevertheless very good audio quality on the decoder-side is obtained due to the fact that the bits which have been saved by not providing any object data anymore from the encoder to the decoder can be used for better encoding the channel data such as by finer quantizing the channel data or by other means for improving the quality or for reducing the encoding loss when enough bits are available.
• the encoder additionally comprises an SAOC encoder and furthermore allows to not only encode objects input into the encoder but to also SAOC encode channel data in order to obtain a good audio quality at even lower required bit rates.
• Further embodiments of the present invention allow a post processing functionality which comprises a binaural renderer and/or a format converter. Furthermore, it is preferred that the whole processing on the decoder side already takes place for a certain high number of loud speakers such as a 22 or 32 channel loudspeaker setup.
• the format converter determines that only a 5.1 output, i.e., an output for a reproduction layout is required which has a lower number than the maximum number of channels, then it is preferred that the format converter controls either the USAC decoder or the SAOC decoder or both devices to restrict the core decoding operation and the SAOC decoding operation so that any channels which are, in the end, nevertheless down mixed into a format conversion are not generated in the decoding.
• the generation of upmixed channels requires decorrelation processing and each decorrelation processing introduces some level of artifacts.
• inventive encoders/decoders cannot only be introduced in mobile devices such as mobile phones, smart phones, notebook computers or navigation devices but can also be used in straightforward desktop computers or any other non-mobile appliances.
• the above implementation i.e. to not generate some channels, may be not optimum, since some information may be lost (such as the level difference between the channels that will be downmixed). This level difference information may not be critical, but may result in a different downmix output signal, if the downmix applies different downmix gains to the upmixed channels.
• An improved solution only switches off the decorrelation in the upmix, but still generates all upmix channels with correct level differences (as signalled by the parametric SAC).
• the second solution results in a better audio quality, but the first solution results in greater complexity reduction.
• Fig. 1 illustrates a first embodiment of an encoder
• Fig. 2 illustrates a first embodiment of a decoder
• Fig. 3 illustrates a second embodiment of an encoder
• Fig. 4 illustrates a second embodiment of a decoder; illustrates a third embodiment of an encoder; illustrates a third embodiment of a decoder; illustrates a map indicating individual modes in which the encoders/decoders in accordance with embodiments of the present invention can be operated; illustrates a specific implementation of the format converter; illustrates a specific implementation of the binaural converter; illustrates a specific implementation of the core decoder; and Fig. 1 1 illustrates a specific implementation of an encoder for processing a quad channel element (QCE) and the corresponding QCE decoder.
• QCE quad channel element
• Fig. 1 illustrates an encoder in accordance with an embodiment of the present invention.
• the encoder is configured for encoding audio input data 101 to obtain audio output data 501 .
• the encoder comprises an input interface for receiving a plurality of audio channels indicated by CH and a plurality of audio objects indicated by OBJ.
• the input interface 100 additionally receives metadata related to one or more of the plurality of audio objects OBJ.
• the encoder comprises a mixer 200 for mixing the plurality of objects and the plurality of channels to obtain a plurality of pre-mixed channels, wherein each pre-mixed channel comprises audio data of a channel and audio data of at least one object.
• the encoder comprises a core encoder 300 for core encoding core encoder input data, a metadata compressor 400 for compressing the metadata related to the one or more of the plurality of audio objects.
• the encoder can comprise a mode controller 600 for controlling the mixer, the core encoder and/or an output interface 500 in one of several operation modes, wherein in the first mode, the core encoder is configured to encode the plurality of audio channels and the plurality of audio objects received by the input interface 100 without any interaction by the mixer, i.e., without any mixing by the mixer 200. In a second mode, however, in which the mixer 200 was active, the core encoder encodes the plurality of mixed channels, i.e., the output generated by block 200.
• the metadata indicating positions of the audio objects are already used by the mixer 200 to render the objects onto the channels as indicated by the metadata.
• the mixer 200 uses the metadata related to the plurality of audio objects to pre-render the audio objects and then the pre-rendered audio objects are mixed with the channels to obtain mixed channels at the output of the mixer.
• any objects may not necessarily be transmitted and this also applies for compressed metadata as output by block 400.
• the core encoder 300 or the metadata compressor 400 respectively.
• Fig. 3 illustrates a further embodiment of an encoder which, additionally, comprises an SAOC encoder 800.
• the SAOC encoder 800 is configured for generating one or more transport channels and parametric data from spatial audio object encoder input data.
• the spatial audio object encoder input data are objects which have not been processed by the pre-renderer/mixer.
• the pre- renderer/mixer has been bypassed as in the mode one where an individual channel/object coding is active, all objects input into the input interface 100 are encoded by the SAOC encoder 800.
• the output of the whole encoder illustrated in Fig. 3 is an MPEG 4 data stream having the container-like structures for individual data types.
• the metadata is indicated as ⁇ " data and the metadata compressor 400 in Fig. 1 corresponds to the OAM encoder 400 to obtain compressed OAM data which are input into the USAC encoder 300 which, as can be seen in Fig. 3, additionally comprises the output interface to obtain the MP4 output data stream not only having the encoded channel/object data but also having the compressed OAM data.
• Fig. 5 illustrates a further embodiment of the encoder, where in contrast to Fig. 3, the SAOC encoder can be configured to either encode, with the SAOC encoding algorithm, the channels provided at the pre-renderer/mixer 200not being active in this mode or, alternatively, to SAOC encode the pre-rendered channels plus objects.
• the SAOC encoder 800 can operate on three different kinds of input data, i.e., channels without any pre-rendered objects, channels and pre-rendered objects or objects alone.
• it is preferred to provide an additional OAM decoder 420 in Fig. 5 so that the SAOC encoder 800 uses, for its processing, the same data as on the decoder side, i.e., data obtained by a lossy compression rather than the original OAM data.
• the Fig. 5 encoder can operate in several individual modes.
• the Fig. 5 encoder can additionally operate in a third mode in which the core encoder generates the one or more transport channels from the individual objects when the pre- renderer/mixer 200 was not active.
• the SAOC encoder 800 can generate one or more alternative or additional transport channels from the original channels, i.e., again when the pre-renderer/mixer 200 corresponding to the mixer 200 of Fig. 1 was not active.
• the SAOC encoder 800 can encode, when the encoder is configured in the fourth mode, the channels plus pre-rendered objects as generated by the pre-renderer/mixer.
• the fourth mode the lowest bit rate applications will provide good quality due to the fact that the channels and objects have completely been transformed into individual SAOC transport channels and associated side information as indicated in Figs. 3 and 5 as "SAOC-SI" and, additionally, any compressed metadata do not have to be transmitted in this fourth mode.
• Fig. 2 illustrates a decoder in accordance with an embodiment of the present invention.
• the decoder receives, as an input, the encoded audio data, i.e., the data 501 of Fig. 1 .
• the decoder comprises a metadata decompressor 1400, a core decoder 1300, an object processor 1200, a mode controller 1600 and a postprocessor 1700.
• the audio decoder is configured for decoding encoded audio data and the input interface is configured for receiving the encoded audio data, the encoded audio data comprising a plurality of encoded channels and the plurality of encoded objects and compressed metadata related to the plurality of objects in a certain mode.
• the core decoder 1300 is configured for decoding the plurality of encoded channels and the plurality of encoded objects and, additionally, the metadata decompressor is configured for decompressing the compressed metadata.
• the object processor 1200 is configured for processing the plurality of decoded objects as generated by the core decoder 1300 using the decompressed metadata to obtain a predetermined number of output channels comprising object data and the decoded channels.
• the postprocessor 1700 is configured for converting the number of output channels 1205 into a certain output format which can be a binaural output format or a loudspeaker output format such as a 5.1 , 7.1 , etc., output format.
• the decoder comprises a mode controller 1600 which is configured for analyzing the encoded data to detect a mode indication. Therefore, the mode controller 1600 is connected to the input interface 1 100 in Fig. 2. However, alternatively, the mode controller does not necessarily have to be there. Instead, the flexible decoder can be preset by any other kind of control data such as a user input or any other control.
• the audio decoder in Fig. 2 and, preferably controlled by the mode controller 1600, is configured to either bypass the object processor and to feed the plurality of decoded channels into the postprocessor 1700. This is the operation in mode 2, i.e., in which only pre-rendered channels are received, i.e., when mode 2 has been applied in the encoder of Fig. 1 .
• the object processor 1200 is not bypassed, but the plurality of decoded channels and the plurality of decoded objects are fed into the object processor 1200 together with decompressed metadata generated by the metadata decompressor 1400.
• the indication whether mode 1 or mode 2 is to be applied is included in the encoded audio data and then the mode controller 1600 analyses the encoded data to detect a mode indication.
• Mode 1 is used when the mode indication indicates that the encoded audio data comprises encoded channels and encoded objects
• mode 2 is applied when the mode indication indicates that the encoded audio data does not contain any audio objects, i.e., only contain pre-rendered channels obtained by mode 2 of the Fig. 1 encoder.
• Fig. 4 illustrates a preferred embodiment compared to the Fig. 2 decoder and the embodiment of Fig. 4 corresponds to the encoder of Fig. 3.
• the decoder in Fig. 4 comprises an SAOC decoder 1800.
• the object processor 1200 of Fig. 2 is implemented as a separate object renderer 1210 and the mixer 1220 while, depending on the mode, the functionality of the object renderer 1210 can also be implemented by the SAOC decoder 1800.
• the postprocessor 1700 can be implemented as a binaural renderer 1710 or a format converter 1720.
• a direct output of data 1205 of Fig. 2 can also be implemented as illustrated by 1730. Therefore, it is preferred to perform the processing in the decoder on the highest number of channels such as 22.2 or 32 in order to have flexibility and to then post-process if a smaller format is required.
• the object processor 1200 comprises the SAOC decoder 1800 and the SAOC decoder is configured for decoding one or more transport channels output by the core decoder and associated parametric data and using decompressed metadata to obtain the plurality of rendered audio objects.
• the OAM output is connected to box 1800.
• the object processor 1200 is configured to render decoded objects output by the core decoder which are not encoded in SAOC transport channels but which are individually encoded in typically single channeled elements as indicated by the object renderer 1210. Furthermore, the decoder comprises an output interface corresponding to the output 1730 for outputting an output of the mixer to the loudspeakers.
• the object processor 1200 comprises a spatial audio object coding decoder 1800 for decoding one or more transport channels and associated parametric side information representing encoded audio objects or encoded audio channels, wherein the spatial audio object coding decoder is configured to transcode the associated parametric information and the decompressed metadata into transcoded parametric side information usable for directly rendering the output format, as for example defined in an earlier version of SAOC.
• the postprocessor 1700 is configured for calculating audio channels of the output format using the decoded transport channels and the transcoded parametric side information.
• the processing performed by the post processor can be similar to the MPEG Surround processing or can be any other processing such as BCC processing or so.
• the object processor 1200 comprises a spatial audio object coding decoder 1800 configured to directly upmix and render channel signals for the output format using the decoded (by the core decoder) transport channels and the parametric side information
• the object processor 1200 of Fig. 2 additionally comprises the mixer 1220 which receives, as an input, data output by the USAC decoder 1300 directly when pre-rendered objects mixed with channels exist, i.e., when the mixer 200 of Fig. 1 was active. Additionally, the mixer 1220 receives data from the object renderer performing object rendering without SAOC decoding. Furthermore, the mixer receives SAOC decoder output data, i.e., SAOC rendered objects.
• the mixer 1220 is connected to the output interface 1730, the binaural renderer 1710 and the format converter 1720.
• the binaural renderer 1710 is configured for rendering the output channels into two binaural channels using head related transfer functions or binaural room impulse responses (BRIR).
• BRIR binaural room impulse responses
• the format converter 1720 is configured for converting the output channels into an output format having a lower number of channels than the output channels 1205 of the mixer and the format converter 1720 requires information on the reproduction layout such as 5.1 speakers or so.
• the Fig. 6 decoder is different from the Fig. 4 decoder in that the SAOC decoder cannot only generate rendered objects but also rendered channels and this is the case when the Fig. 5 encoder has been used and the connection 900 between the channels/pre- rendered objects and the SAOC encoder 800 input interface is active.
• a vector base amplitude panning (VBAP) stage 1810 is configured which receives, from the SAOC decoder, information on the reproduction layout and which outputs a rendering matrix to the SAOC decoder so that the SAOC decoder can, in the end, provide rendered channels without any further operation of the mixer in the high channel format of 1205, i.e., 32 loudspeakers.
• the VBAP block preferably receives the decoded OAM data to derive the rendering matrices. More general, it preferably requires geometric information not only of the reproduction layout but also of the positions where the input signals should be rendered to on the reproduction layout. This geometric input data can be OAM data for objects or channel position information for channels that have been transmitted using SAOC.
• the VBAP state 1810 can already provide the required rendering matrix for the e.g., 5.1 output.
• the SAOC decoder 1800 then performs a direct rendering from the SAOC transport channels, the associated parametric data and decompressed metadata, a direct rendering into the required output format without any interaction of the mixer 1220.
• the mixer will put together the data from the individual input portions, i.e., directly from the core decoder 1300, from the object renderer 1210 and from the SAOC decoder 1800.
• FIG. 7 is discussed for indicating certain encoder/decoder modes which can be applied by the inventive highly flexible and high quality audio encoder/decoder concept.
• the mixer 200 in the Fig. 1 encoder is bypassed and, therefore, the object processor in the Fig. 2 decoder is not bypassed.
• the mixer 200 in Fig. 1 is active and the object processor in Fig. 2 is bypassed.
• mode 3 requires that, on the decoder side illustrated in Fig. 4, the SAOC decoder is only active for objects and generates rendered objects.
• the SAOC encoder is configured for SAOC encoding pre-rendered channels, i.e., the mixer is active as in the second mode.
• the SAOC decoding is preformed for pre-rendered objects so that the object processor is bypassed as in the second coding mode.
• a fifth coding mode exists which can by any mix of modes 1 to 4.
• a mix coding mode will exist when the mixer 1220 in Fig. 6 receives channels directly from the USAC decoder and, additionally, receives channels with pre-rendered objects from the USAC decoder.
• objects are encoded directly using, preferably, a single channel element of the USAC decoder.
• the object renderer 1210 will then render these decoded objects and forward them to the mixer 1220.
• several objects are additionally encoded by an SAOC encoder so that the SAOC decoder will output rendered objects to the mixer and/or rendered channels when several channels encoded by SAOC technology exist.
• Each input portion of the mixer 1220 can then, exemplarily, have at least a potential for receiving the number of channels such as 32 as indicated at 1205.
• the mixer could receive 32 channels from the USAC decoder and, additionally, 32 pre- rendered/mixed channels from the USAC decoder and, additionally, 32 "channels" from the object renderer and, additionally, 32 "channels” from the SAOC decoder, where each "channel" between blocks 1210 and 1218 on the one hand and block 1220 on the other hand has a contribution of the corresponding objects in a corresponding loudspeaker channel and then the mixer 1220 mixes, i.e., adds up the individual contributions for each loudspeaker channel.
• the encoding/decoding system is based on an MPEG-D USAC codec for coding of channel and object signals.
• MPEG SAOC technology has been adapted. Three types of renderers perform the task of rendering objects to channels, rendering channels to headphones or rendering channels to a different loudspeaker setup.
• object signals are explicitly transmitted or parametrically encoded using SAOC, the corresponding object metadata information is compressed and multiplexed into the encoded output data.
• the pre-renderer/mixer 200 is used to convert a channel plus object input scene into a channel scene before encoding. Functionally, it is identical to the object renderer/mixer combination on the decoder side as illustrated in Fig. 4 or Fig. 6 and as indicated by the object processor 1200 of Fig. 2. Pre-rendering of objects ensures a deterministic signal entropy at the encoder input that is basically independent of the number of simultaneously active object signals. With pre-rendering of objects, no object metadata transmission is required. Discrete object signals are rendered to the channel layout that the encoder is configured to use. The weights of the objects for each channel are obtained from the associated object metadata OAM as indicated by arrow 402.
• a USAC technology is preferred. It handles the coding of the multitude of signals by creating channel and object mapping information (the geometric and semantic information of the input channel and object assignment).
• This mapping information describes how input channels and objects are mapped to USAC channel elements as illustrated in Fig. 10, i.e., channel pair elements (CPEs), single channel elements (SCEs), channel quad elements (QCEs) and the corresponding information is transmitted to the core decoder from the core encoder. All additional payloads like SAOC data or object metadata have been passed through extension elements and have been considered in the encoder's rate control.
• the coding of objects is possible in different ways, depending on the rate/distortion requirements and the interactivity requirements for the renderer. The following object coding variants are possible:
• Prerendered objects Object signals are prerendered and mixed to the 22.2 channel signals before encoding. The subsequent coding chain sees 22.2 channel signals.
• Discrete object waveforms Objects are supplied as monophonic waveforms to the encoder.
• the encoder uses single channel elements SCEs to transmit the objects in addition to the channel signals.
• the decoded objects are rendered and mixed at the receiver side. Compressed object metadata information is transmitted to the receiver/renderer alongside.
• Parametric object waveforms Object properties and their relation to each other are described by means of SAOC parameters.
• the down-mix of the object signals is coded with USAC.
• the parametric information is transmitted alongside.
• the number of downmix channels is chosen depending on the number of objects and the overall data rate.
• Compressed object metadata information is transmitted to the SAOC renderer.
• the SAOC encoder and decoder for object signals are based on MPEG SAOC technology.
• the system is capable of recreating, modifying and rendering a number of audio objects based on a smaller number of transmitted channels and additional parametric data (OLDs, lOCs (Inter Object Coherence), DMGs (Down Mix Gains)).
• the additional parametric data exhibits a significantly lower data rate than required for transmitting all objects individually, making the coding very efficient.
• the SAOC encoder takes as input the object/channel signals as monophonic waveforms and outputs the parametric information (which is packed into the 3D-Audio bitstream) and the SAOC transport channels (which are encoded using single channel elements and transmitted).
• the SAOC decoder reconstructs the object/channel signals from the decoded SAOC transport channels and parametric information, and generates the output audio scene based on the reproduction layout, the decompressed object metadata information and optionally on the user interaction information.
• the associated metadata that specifies the geometrical position and volume of the object in 3D space is efficiently coded by quantization of the object properties in time and space.
• the compressed object metadata cOAM is transmitted to the receiver as side information.
• the volume of the object may comprise information on a spatial extent and/or information of the signal level of the audio signal of this audio object.
• the object renderer utilizes the compressed object metadata to generate object waveforms according to the given reproduction format. Each object is rendered to certain output channels according to its metadata. The output of this block results from the sum of the partial results.
• the channel based waveforms and the rendered object waveforms are mixed before outputting the resulting waveforms (or before feeding them to a postprocessor module like the binaural renderer or the loudspeaker renderer module).
• the binaural renderer module produces a binaural downmix of the multichannel audio material, such that each input channel is represented by a virtual sound source.
• the processing is conducted frame-wise in QMF (Quadrature Mirror Filterbank) domain.
• QMF Quadrature Mirror Filterbank
• Fig. 8 illustrates a preferred embodiment of the format converter 1720.
• the loudspeaker renderer or format converter converts between the transmitter channel configuration and the desired reproduction format. This format converter performs conversions to lower number of output channels, i.e., it creates downmixes.
• a downmixer 1722 which preferably operates in the QMF domain receives mixer output signals 1205 and outputs loudspeaker signals.
• a controller 1724 for configuring the downmixer 1722 is provided which receives, as a control input, a mixer output layout, i.e., the layout for which data 1205 is determined and a desired reproduction layout is typically been input into the format conversion block 1720 illustrated in Fig. 6.
• the controller 1724 preferably automatically generates optimized downmix matrices for the given combination of input and output formats and applies these matrices in the downmixer block 1722 in the downmix process.
• the format converter allows for standard loudspeaker configurations as well as for random configurations with non-standard loudspeaker positions.
• the SAOC decoder is designed to render to the predefined channel layout such as 22.2 with a subsequent format conversion to the target reproduction layout.
• the SAOC decoder is implemented to support the "low power" mode where the SAOC decoder is configured to decode to the reproduction layout directly without the subsequent format conversion.
• the SAOC decoder 1800 directly outputs the loudspeaker signal such a the 5.1 loudspeaker signals and the SAOC decoder 1800 requires the reproduction layout information and the rendering matrix so that the vector base amplitude panning or any other kind of processor for generating downmix information can operate.
• Fig. 9 illustrates a further embodiment of the binaural renderer 1710 of Fig. 6.
• the binaural rendering is required for headphones attached to such mobile devices or for loudspeakers directly attached to typically small mobile devices.
• constraints may exist to limit the decoder and rendering complexity.
• 22.2 channel material is downmixed by the downmixer 1712 to a 5.1 intermediate downmix or, alternatively, the intermediate downmix is directly calculated by the SAOC decoder 1800 of Fig. 6 in a kind of a "shortcut" mode.
• the binaural rendering only has to apply ten HRTFs (Head Related Transfer Functions) or BRIR functions for rendering the five individual channels at different positions in contrast to apply 44 HRTF for BRIR functions if the 22.2 input channels would have already been directly rendered.
• HRTFs Head Related Transfer Functions
• BRIR functions for rendering the five individual channels at different positions in contrast to apply 44 HRTF for BRIR functions if the 22.2 input channels would have already been directly rendered.
• the convolution operations necessary for the binaural rendering require a lot of processing power and, therefore, reducing this processing power while still obtaining an acceptable audio quality is particularly useful for mobile devices.
• control line 1727 comprises controlling the decoder 1300 to decode to a lower number of channels, i.e., skipping the complete OTT processing block in the decoder or a format converting to a lower number of channels and, as illustrated in Fig. 9, the binaural rendering is performed for the lower number of channels.
• the same processing can be applied not only for binaural processing but also for a format conversion as illustrated by line 1727 in Fig. 6.
• an efficient interfacing between processing blocks is required. Particularly in Fig. 6, the audio signal path between the different processing blocks is depicted.
• all these processing blocks provide a QMF or a hybrid QMF interface to allow passing audio signals between each other in the QMF domain in an efficient manner. Additionally, it is preferred to implement the mixer module and the object renderer module to work in the QMF or hybrid QMF domain as well.
• Fig. 1 1 in order to explain quad channel elements (QCE).
• QCE quad channel elements
• a quad channel element requires four input channels 90 and outputs an encoded QCE element 91 .
• TTO Two To One
• additional joint stereo coding tools e.g. MS-Stereo
• the QCE element not only comprises two jointly stereo coded downmix channels and optionally two jointly stereo coded residual channels and, additionally, parametric data derived from the, for example, two TTO boxes.
• a structure is applied where the joint stereo decoding of the two downmix channels and optionally of the two residual channels is applied and in a second stage with two OTT boxes the downmix and optional residual channels are upmixed to the four output channels.
• the core encoder/decoder additionally uses a joint channel coding of a group of four channels.
• the encoder has been operated in a 'constant rate with bit-reservoir' fashion, using a maximum of 6144 bits per channel as rate buffer for the dynamic data. All additional payloads like SAOC data or object metadata have been passed through extension elements and have been considered in the encoder's rate control.
• the binaural renderer module produces a binaural downmix of the multichannel audio material, such that each input channel (excluding the LFE channels) is represented by a virtual sound source.
• the processing is conducted frame-wise in QMF domain.
• the binauralization is based on measured binaural room impulse responses.
• the direct sound and early reflections are imprinted to the audio material via a convolutional approach in a pseudo-FFT domain using a fast convolution on-top of the QMF domain.
• a block or device corresponds to a method step or a feature of a method step.
• aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus.
• some one or more of the most important method steps may be executed by such an apparatus.
• embodiments of the invention can be implemented in hardware or in software.
• the implementation can be performed using a non-transitory storage medium such as a digital storage medium, for example a floppy disc, a DVD, a Blu-Ray, a CD, a ROM, a PROM, and EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. Therefore, the digital storage medium may be computer readable.
• Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.
• embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer.
• the program code may, for example, be stored on a machine readable carrier.
• inventions comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier.
• an embodiment of the inventive method is, therefore, a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.
• a further embodiment of the inventive method is, therefore, a data carrier (or a digital storage medium, or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein.
• the data carrier, the digital storage medium or the recorded medium are typically tangible and/or non- transitionary.
• a further embodiment of the invention method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein.
• the data stream or the sequence of signals may, for example, be configured to be transferred via a data communication connection, for example, via the internet.
• a further embodiment comprises a processing means, for example, a computer or a programmable logic device, configured to, or adapted to, perform one of the methods described herein.
• a further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein.
• a further embodiment according to the invention comprises an apparatus or a system configured to transfer (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver.
• the receiver may, for example, be a computer, a mobile device, a memory device or the like.
• the apparatus or system may, for example, comprise a file server for transferring the computer program to the receiver .
• a programmable logic device for example, a field programmable gate array
• a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein.
• the methods are preferably performed by any hardware apparatus.

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