Simultaneous broadcaster-mixed and receiver-mixed supplementary audio services

An audio encoding method, comprising:

• inputting a primary signal (X) in N-channel format and a secondary signal (Y);
• providing a reduced primary signal (Xm) in M-channel format based on the primary signal, wherein M<N;
• phase-inverting the reduced primary signal and additively mixing it with the secondary signal to obtain a combined signal (Z);
• and
• outputting the primary signal (X) and the combined signal (Z).

An audio encoder, comprising:

• a channel reduction processor for providing a signal in M-channel format based on a signal in N-channel format, wherein M<N;
• a mixer for additively mixing two signals;
• and
• a phase inverter connected between an output side of the channel reduction processor and an input side of the mixer,
• wherein the channel reduction processor is configured to provide, based on a primary signal (X), a reduced primary signal (Xm) supplied to the phase inverter, and wherein the reduced primary signal after being phase inverted is mixed, by the mixer, with a secondary signal (Y) into a combined signal (Z).

An audio decoding method, comprising:

• inputting a primary signal (X) and a combined signal (Z);
• providing a reduced primary signal (Xm) based on the primary signal (X);
• providing a secondary signal (Y) by additively mixing the combined signal and the reduced primary signal (Xm);
• providing an extended signal (Xe) by additively mixing the primary signal (X) and the secondary signal (Y);
• and
• outputting the extended signal.

A data carrier storing:

• a primary signal (X) in N-channel format;
• and
• a combined signal (Z) comprising a phase-inverted reduced primary signal (Xm) in M-channel format additively mixed with a secondary signal (Y), wherein M<N and the secondary signal relates to a supplementary audio service associated with the primary signal,
• said primary signal (X) comprising data enabling a copy of said reduced primary signal (Xm) to be restored in accordance with a downmix specification, whereby additive mixing of the copy of said reduced primary signal and the combined signal (Z) will yield the secondary signal (Y).

A dual-mode audio decoder, comprising:

• a channel reduction processor for providing a signal in M-channel format based on a signal in N-channel format, wherein M<N;
• and
• an first and a second mixer, each configured to additively mix two signals, wherein the audio decoder is operable in:
• a) a basic mode, in which the decoder inputs a primary signal and outputs the primary signal;
• and
• b) an extended mode, in which:
• the decoder inputs a primary signal (X) and a combined signal (Z);
• the channel reduction processor provides a reduced primary signal (Xm) based on the primary signal (X);
• the first mixer provides a secondary signal (Y) by additively mixing the combined signal (Z) and the reduced primary signal (Xm);
• and
• the second mixer provides an extended signal (Xe) by additively mixing the primary signal (X) and the secondary signal (Y), which extended signal is output by the decoder.