News Column

Patent Issued for Audio Decoder

February 5, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventor Breebaart, Dirk Jeroen (Eindhoven, NL), filed on January 7, 2008, was published online on January 21, 2014.

The patent's assignee for patent number 8634577 is Koninklijke Philips N.V. (Eindhoven, NL).

News editors obtained the following quote from the background information supplied by the inventors: "In (parametric) spatial audio (en)coders, parameters are extracted from the original audio signals so as to produce a reduced number of down-mix audio signals (for example only a single down-mix signal corresponding to a mono, or two down-mix signals for a stereo down mix), and a corresponding set of parameters describing the spatial properties of the original audio signal. In (parametric) spatial audio decoders, the spatial properties described by the transmitted spatial parameters are used to recreate a spatial multi-channel signal, which closely resembles the original multi-channel audio signal.

"Recently, techniques for processing and manipulating of individual audio objects at the decoding side have attracted significant interest. For example, within the MPEG framework, a workgroup has been started on object-based spatial audio coding. The aim of this workgroup is to 'explore new technology and reuse of current MPEG Surround components and technologies for the bit rate efficient coding of multiple sound sources or objects into a number of down-mix channels and corresponding spatial parameters'. In other words, the aim is to encode multiple audio objects in a limited set of down-mix channels with corresponding parameters. At the decoder side, users interact with the content for example by repositioning the individual objects.

"Such interaction with the content is easily realized in object-oriented decoders. It is then realized by including a rendering that follows the decoding. Said rendering is combined with the decoding to prevent the need of determining individual objects. The currently available dedicated rendering comprises positioning of objects, volume adjusting, or equalization of the rendered audio signals.

"One disadvantage of the known object-oriented decoders with the incorporated rendering is that they permit a limited set of manipulations of objects, because they do not produce or operate on the individual objects. On the other hand explicit decoding of the individual audio objects is very costly and inefficient."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "It is an object of the invention to provide an enhanced decoder for decoding audio objects that allows a wider range of manipulations of objects without a need for decoding the individual audio objects for this purpose.

"This object is achieved by an audio decoder according to the invention. It is assumed that a set of objects, each with its corresponding waveform, has previously been encoded in an object-oriented encoder, which generates a down-mix audio signal (a single signal in case of a single channel), said down-mix audio signal being a down-mix of a plurality of audio objects and corresponding parametric data. The parametric data comprises a set of object parameters for each of the different audio objects. The receiver receives said down-mix audio signal and said parametric data. This down-mix audio signal is further fed into effect means that generate modified down-mix audio signal by applying effects to estimates of audio signals corresponding to selected audio objects comprised in the down-mix audio signal. Said estimates of audio signals are derived based on the parametric data. The modified down-mix audio signal is further fed into decoding means, or rendering means, or combined with the output of rendering means depending on a type of the applied effect, e.g. an insert or send effect. The decoding means decode the audio objects from the down-mix audio signal fed into the decoding means, said down-mix audio signal being the originally received down-mix audio signal or the modified down-mix audio signal. Said decoding is performed based on the parametric data. The rendering means generate a spatial output audio signal from the audio objects obtained from the decoding means and optionally from the effect means, depending on the type of the applied effect.

"The advantage of the decoder according to the invention is that in order to apply various types of effects it is not needed that the object, to which the effect is to be applied, is available. Instead, the invention proposes to apply the effect to the estimated audio signals corresponding to the objects before or in parallel to the actual decoding. Therefore, explicit object decoding is not required, and the rendering emerged in the decoder is preserved.

"In an embodiment, the decoder further comprises modifying means for modifying the parametric data when a spectral or temporal envelope of an estimated audio signal corresponding to the object or plurality of objects is modified by the insert effect.

"An example of such an effect is a non-linear distortion that generates additional high frequency spectral components, or a multi-band compressor. If the spectral characteristic of the modified audio signal has changed, applying the unmodified parameters comprised in the parametric data, as received, might lead to undesired and possibly annoying artifacts. Therefore, adapting the parameters to match the new spectral or temporal characteristics improves the quality of the resulting rendered audio signal.

"In an embodiment, the generation of the estimated audio signals corresponding to an audio object or plurality of objects comprises time/frequency dependent scaling of the down-mix audio signals based on the power parameters corresponding to audio objects, said power parameters being comprised in the received parametric data.

"The advantage of this estimation is that it comprises a multiplication of the down-mix audio signal. This makes the estimation process simple and efficient.

"In an embodiment, the decoding means comprise a decoder in accordance with the MPEG Surround standard and conversion means for converting the parametric data into parametric data in accordance with the MPEG Surround standard.

"The advantage of using the MPEG Surround decoder is that this type of decoder is used as a rendering engine for an object-oriented decoder. In this case, the object-oriented parameters are combined with user-control data and converted to MPEG Surround parameters, such as level differences and correlation parameters between channels (pairs). Hence the MPEG Surround parameters result from the combined effect of object-oriented parameters, i.e. transmitted information, and the desired rendering properties, i.e. user-controllable information set at the decoder side. In such a case no intermediate object signals are required.

"The invention further provides a receiver and a communication system, as well as corresponding methods.

"In an embodiment, the insert and send effects are applied simultaneously. Using of, for example, insert effects does not exclude use of send effects, and vice versa.

"The invention further provides a computer program product enabling a programmable device to perform the method according to the invention."

For additional information on this patent, see: Breebaart, Dirk Jeroen. Audio Decoder. U.S. Patent Number 8634577, filed January 7, 2008, and published online on January 21, 2014. Patent URL:

Keywords for this news article include: Koninklijke Philips N.V.

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Source: Journal of Engineering

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