FIG. 1 illustrates an example of a conventional encoder for encoding multi-object or multi-channel audio signals. Referring to the drawing, a Spatial Audio Coding (SAC) encoder 101 is presented as an example of a conventional multi-object or multi-channel audio signal encoder, and it extracts spatial cues, which are to be described later, from the input signals, i.e., multi-object or multi-channel audio signals and transmits the spatial cues, while down-mixing the audio signals and transmits them in the form of mono or stereo signals.
SAC technology relates to a method of representing multi-object or multi-channel audio signals as down-mixed mono or stereo signals and spatial cue information, and transmitting and recovering them. The SAC technology can transmit high-quality multi-channel signals even at a low bit rate. The SAC technology focuses on analyzing multi-object or multi-channel audio signals according to each sub-band, and recovering original signals from the down-mixed signals based on the spatial cue information for each sub-band. Thus, the spatial cue information includes significant information needed for recovering the original signals in a decoding process, and the information becomes a major factor that determines the sound quality of the audio signals recovered in an SAC decoding device. Moving Picture Experts Group (MPEG) based on SAC technology is undergoing standardization in the name of MPEG Surround, and Channel Level Difference (CLD) is used as spatial cue.
The present invention is directed to an apparatus and method for controlling rendering of multi-object or multi-channel audio signals based on spatial cue transmitted from an encoder, while the multi-object or multi-channel audio signals are down-mixed and transmitted from the encoder and decoded.
Conventionally, a graphic equalizer equipped with a frequency analyzer was usually utilized to recover mono or stereo audio signals. The multi-object or multi-channel audio signals can be positioned diversely in a space. However, the positions of audio signals generated from the multi-object or multi-channel audio signals are recognized and recovered uniquely to a decoding device in the current technology.