Method and apparatus for processing two or more initially decoded audio signals received or replayed from a bitstream
View Patent ↗In the MPEG-4 standard ISO/IEC 14496:2001 several audio objects that can be coded with different MPEG-4 format coding types can together form a composed audio system representing a single soundtrack from the several audio substreams. In a receiver the multiple audio objects are decoded separately, but not directly played back to a listener. Instead, transmitted instructions for mixdown are used to prepare a single soundtrack. Mixdown conflicts can occur in case the audio signals to be combined have different channel numbers or configurations. According to the invention an additional audio channel configuration node is used that tags the correct channel configuration information items to the decoded audio data streams to be presented. The invention enables the content provider to set the channel configuration in such a way that the presenter at receiver side can produce a correct channel presentation under all circumstances. An escape code value in the channel configuration data facilitates correct handling of not yet defined channel combinations.
1. Method for processing two or more decoded but not yet combined individual audio signals received or replayed from different audio sources, wherein at least two of said decoded audio signals have a different number of channels per decoded audio signal and different channel configurations for channel to speaker mapping, and wherein said decoded audio signals are to be combined by mixing and/or switching before being presented in a final channel configuration, and wherein to each one of said decoded audio signals a corresponding specific channel configuration information item representing corresponding number of channels and channel configuration for said each decoded audio signal is attached and the channel configuration information items for said two or more decoded audio signals can represent conflicting numbers of channels per decoded audio signal and conflicting channel configurations, said method comprising:
controlling said mixing and/or switching such that in case of conflicting numbers of channels and conflicting channel configurations the number of the channels and the configuration of the channels to be output following said mixing and/or following said switching is determined by specific mixing and/or switching information provided from a content provider or broadcaster that is embedded in at least one of said audio signals, so as to resolve such conflict, and
attaching to the combined data stream to be presented a correspondingly updated channel configuration information item, wherein said correspondingly updated channel configuration information item represents said determined number of channels and configuration.
2. Method according to claim 1 , wherein said bitstream has MPEG-4 format.