Audio mixing

An audio mixing apparatus for mixing at least two audio signals included in a set of audio signals provided by a set of respective audio channels, the apparatus including:

• a mixing stack in which the set of audio channels are arranged using their respective channel identifiers, wherein one channel identifier, corresponding to one of the audio channels, is stored at each level of the stack;
• a mixer control unit for regularly updating the mixing stack such that a channel identifier corresponding to an audio channel which previously was active but now has become inactive is relocated below the channel identifiers corresponding to active audio channels;
• and
• a mixer unit for producing a mixed audio output signal by mixing audio signals provided by the audio channels corresponding to a predetermined number of topmost channel identifiers stored in the mixing stack,
• wherein if the relocated channel identifier is one of the predetermined number of topmost channel identifiers stored in the mixing stack, the audio signal provided by the corresponding inactive audio channel is part of the mixed audio output signal produced by the mixer unit.

A method of mixing audio signals provided by a set of audio channels, the method including:

• storing channel identifiers for the set of audio channels in a mixing stack such that one channel identifier, corresponding to one of the audio channels, is stored at each level of the mixing stack;
• receiving, for each of the audio channels, audio activity information indicating whether the audio channel is active or inactive;
• updating the mixing stack for selection of audio channels to mix based on the audio activity information received for the audio channels;
• and
• producing a mixed audio output signal by mixing audio signals provided by the audio channels corresponding to the channel identifiers stored above a predetermined threshold level in the updated mixing stack,
• wherein the updating is performed such that a channel identifier corresponding to an audio channel that previously was active but, based on the audio activity information received for the audio channel, now has become inactive, is relocated below the channel identifiers corresponding to the active audio channels, and
• wherein if the relocated channel identifier is above the predetermined threshold level, the audio signal provided by the corresponding inactive audio channel is part of the mixed audio output signal.

An audio mixing apparatus for mixing audio signals provided by a set of audio channels, the apparatus including:

• a mixing stack in which channel identifiers for the audio channels are stored such that one channel identifier, corresponding to one of the audio channels is stored at each level of the mixing stack;
• a mixer control unit configured to receive, for each of the audio channels, audio activity information indicating whether the audio channel is active or inactive, and update the mixing stack based on the audio activity information received for the audio channels;
• and
• a mixer unit for producing a mixed audio output signal by mixing the audio signals provided by the audio channels corresponding to the channel identifiers stored above a predetermined threshold level in the updated mixing stack,
• wherein the mixer control unit is configured to update the mixing stack such that a channel identifier corresponding to an audio channel that previously was active but, based on the audio activity information received for the audio channel, now has become inactive is relocated below the channel identifiers corresponding to the active audio channels, and
• wherein if the relocated channel identifier is above the predetermined threshold level, the audio signal provided by the corresponding inactive audio channel is part of the mixed audio output signal.