Many portable playback devices cannot decode and playback encoded audio content having wide bandwidth and wide dynamic range with consistent loudness and intelligibility unless the encoded audio content has been prepared specially for these devices. This problem can be overcome by including with the encoded content some metadata that specifies a suitable dynamic range compression profile by either absolute values or differential values relative to another known compression profile. A playback device may also adaptively apply gain and limiting to the playback audio. Implementations in encoders, in transcoders and in decoders are disclosed.

Apparatuses and methods are described to identify desired audio. A first input of an apparatus is configured to receive a main signal. A second input of the apparatus is configured to receive a reference signal. A normalizer is configured to normalize a compressed main signal by a compressed reference signal to create a normalized main signal. A single channel normalized voice threshold comparator is configured to receive as an input the normalized main signal and to output a desired voice activity detection signal.

An electronic apparatus and a method for activating a specified function are provided. The electronic apparatus includes a speaker, an audio signal processor and an application processor. The audio signal processor senses a variation of an acoustic condition of the speaker. The application processor is used for: generating a logic high or low signal in response to the sensed variation of the acoustic condition; interpreting the logic high or low signal as a control signal; and performing an instruction corresponding to the control signal.

A wireless communication device is disclosed. The wireless communication device includes a processor, a memory, a transceiver configured to receive an audio signal, a codec to decode the audio signal, a dynamic range controller and a phoneme processor. The phoneme processor is configured to extract acoustic cues from each frame of the decoded audio signal and to identify a phoneme class in the each frame. The dynamic range controller is configured to apply dynamic range compression on the each frame based on the identified phoneme class.

This disclosure generally pertains to volume control of audio output by a device. A piecewise curve may be used to implement volume control using two or more curves segments. The piecewise curve may be implemented by a signal converter. The curve segments may be selected to provide volume control that provides incremental changes in amplification at mid-level to high level volumes, while providing anticipated amplification at lower volumes which satisfy users' expectations. In some instances, different piecewise curves may be selected for different types of audio so that these different types of audio are provided to users at an expected volume and/or in a meaningful way. When multiple audio outputs occur at a same time, the piecewise curves associated with some of the audio outputs may be dynamically adjusted or updated based on the presence of the other ones of the multiple audio outputs and/or ambient noise.

A limiter circuit is integrated into an RF power amplifier. The limiter circuit automatically starts adding attenuation at the input of the RF power amplifier after a predetermined input power level threshold is exceeded, thereby extending the safe input drive level to protect the amplifier. In a preferred embodiment of the invention, the limiter circuit is implemented using a pseudomorphic high electron mobility transistor (PHEMT) device or a metal semiconductor field effect transistor (MESPET) device. Diode connected transistors or Schottky diodes may also be used in the limiter circuit.

A method for decoding an encoded audio signal is described. The encoded audio signal comprises a sequence of frames, and is indicative of a plurality of different dynamic range control (DRC) profiles for a corresponding plurality of different rendering modes. The method comprises determining a first rendering mode from the plurality of different rendering modes; determining one or more DRC profiles from a subset of DRC profiles comprised within a current frame of the sequence of frames; determining whether at least one of the one or more DRC profiles is applicable to the first rendering mode; selecting a default DRC profile as a current DRC profile, if none of the one or more DRC profiles is applicable to the first rendering mode; wherein definition data of the default DRC profile is known at a decoder; and decoding the current frame using the current DRC profile.

An audio reproduction apparatus is shown and includes an amplifier with a power amplification stage having transistors in a push-pull arrangement. A bias generator biases the transistors with a standing current. A processor receives a data stream comprising digital samples of an analog audio signal and analyzes the peak level of each group. It then determines the appropriate standing currents to maintain Class A operation of the power amplification stage given the peak levels of each of the groups. A digital to analog converter produces an analog input signal for the input stage of the amplifier from the data stream. A feedforward path between the processor and the bias generator allows the standing current to be adjusted prior to the arrival of the analog input signal in the power amplification stage.

An example method includes receiving, from a first playback device of a playback system, a message indicating a first zone configuration, the first zone configuration including at least a first zone associated with at least the first playback device and a second zone associated with at least a second playback device of the playback system; displaying, based on the first zone configuration, at least a first representation corresponding to the first zone and a second representation corresponding to the second zone; receiving an input to form a zone group including each playback device of the playback system; based on the input, transmitting to a third playback device of the playback system, a message indicating a second zone configuration, the second zone configuration comprising a zone group associated with each playback device of the system; and displaying, based on the second zone configuration, a third representation corresponding to the zone group.

An example method includes receiving, from a first playback device of a playback system, a message indicating a first zone configuration, the first zone configuration including at least a first zone associated with at least the first playback device and a second zone associated with at least a second playback device of the playback system; displaying, based on the first zone configuration, at least a first representation corresponding to the first zone and a second representation corresponding to the second zone; receiving an input to form a zone group including each playback device of the playback system; based on the input, transmitting to a third playback device of the playback system, a message indicating a second zone configuration, the second zone configuration comprising a zone group associated with each playback device of the system; and displaying, based on the second zone configuration, a third representation corresponding to the zone group.