ANDROID AUDIOFLINGER PDF

One work around is to generate the tone in something like Audacity and play it through SoundPool or the api of your choice. According to the Android docs. We know that AudioFlinger (Sometimes called AF) is the core of the entire System services in Android fall into two categories, namely Java. 안드로이드의 모든것 분석과 포팅 정리Android Audio System (AudioFlinger) 박철희 1.

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This glossary of audiodlinger terminology includes widely-used generic terms and Android-specific terms. Digital audio terms relate to handling sound using audio signals encoded in digital form. For details, refer to Digital Audio.

Inter-device interconnection technologies connect audio and video components between devices and are readily visible at the external connectors. The HAL implementer and end user should be aware of these terms. Intra-device interconnection technologies connect internal audio components within a given device and are not visible without disassembling the device.

The HAL implementer may need to be aware of these, but not the end user. For details on intra-device interconnections, refer to the following articles:. Audio signal path terms relate to the signal path that audio data follows from an application to the transducer or vice-versa.

Sample rate conversion terms relate to the process of converting from one sampling rate to another. Android-specific terms include terms used only in the Android audio framework and generic terms aneroid have special meaning within Android. Audioflibger and code samples on this page are subject to the audikflinger described in the Content License.

Generic Terms Generic audio-related terms have conventional meanings. Digital Audio Digital audio terms relate to handling sound using audio signals encoded in digital form. For details, refer to audiophile. Accomplished by dropping channels, mixing channels, or more advanced signal processing. Simple mixing without attenuation or limiting has the potential for overflow and clipping. Proprietary audio encoding based on pulse-density modulation. While Pulse Code Modulation PCM encodes a waveform as a sequence of individual audio samples of multiple bits, DSD encodes a waveform as a sequence of bits at a very high sample rate without the concept of samples.

DSD is better suited to content distribution than aydioflinger an internal representation for processing as it can be difficult to apply traditional digital signal processing DSP algorithms to DSD.

For details, refer to Direct Stream Digital. For example, audioflinyer music is playing when a notification arrives, the music ducks while the notification plays. Hardware module or software data structure audiofllnger implements First In, First Out queueing of data.

In an audio context, the data stored in the queue are typically audio frames. FIFO can be implemented by a circular buffer. The audio HAL interface uses audioflinge concept of frames per buffer. HD audio High-Definition audio.

PulseAudio vs. AudioFlinger

Synonym for high-resolution audio but different than Intel High Definition Audio. Hz Units for sample rate or frame rate. Equivalent to HD audio. For details, anfroid to high-resolution audio. The authoring process may reduce the bit depth or sample rate from that of the masters ; distribution formats that preserve the resolution and bit accuracy of masters are the subject of high-resolution audio. As analog values are from a continuous domain and digital values are discrete, ADC and DAC are lossy conversions with respect to amplitude.

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In strict terms, stereo is more than one channel and could be considered multichannel; however, such usage is confusing and thus avoided. For details, refer to buffer underrun. Most common low-level encoding of digital audio.

The audio signal is sampled at a regular interval, called the sample rate, then quantized to discrete values within a particular range depending on the bit depth. A volume ramp is commonly applied when pausing and resuming music to avoid a hard audible transition. While frame rate is more accurate, sample rate is conventionally used to mean frame rate. The effect can also be applied to a mono signal, where it is a type of upmixing. Lossy data conversion is transparent if it is perceptually indistinguishable from the original by a human subject.

For qudioflinger, refer to Transparency. Accomplished by duplication, panning, or more advanced signal processing. Audikflinger interconnect Inter-device interconnection technologies connect audio and video components between devices and are readily visible at the external connectors. Bluetooth Short range wireless technology. Interface for transferring audio and video data.

Specification for a front-panel connector. For details, refer to Intel High Definition Audio. Interconnect for uncompressed PCM. For details, refer to Thunderbolt. For details, refer to USB. Intra-device interconnect Intra-device interconnection technologies connect internal audio components within a given device and are not visible without disassembling the device.

For details on intra-device interconnections, refer to the following articles: Audio Signal Path Audio signal path terms relate to the signal path that audio data follows from an application to the transducer or vice-versa. Module that converts an analog signal continuous in time and amplitude to a digital signal discrete in time and amplitude. Conceptually, an ADC consists of a periodic sample-and-hold followed by a quantizer, although it does not have to be implemented that way.

An ADC is usually preceded by a low-pass filter to remove any high frequency components that are not representable using androir desired sample rate.

For details, refer to Analog-to-digital converter. Main general-purpose computer on a mobile device.

In strict terms, codec is reserved for modules that both encode and decode but can be used loosely to refer to only one of these. For details, refer to Audio codec.

Module that converts a digital signal discrete in time and amplitude to an analog signal continuous in time and amplitude. Often followed by a low-pass filter to remove high-frequency components introduced by digital quantization.

For details, refer to Digital-to-analog converter. Optional component typically located after the application processor for output or before the application processor for input.

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Primary purpose is to off-load the application processor and provide signal processing features at a lower power cost. Form of modulation used to represent an analog signal by a digital signal, where the relative density of 1s versus 0s indicates the signal level.

Commonly used by digital to analog converters. For details, refer to Pulse-density modulation. Form of modulation used to represent an analog signal by a digital signal, where the relative width of a digital pulse indicates the signal level.

Commonly used by analog-to-digital converters. For details, refer to Pulse-width modulation.

In audio, the physical quantity is sound pressure, and the transducers are the loudspeaker and microphone. For aidioflinger, refer to Transducer. Sample Rate Conversion Sample rate conversion terms relate to the process of converting from one sampling rate to another. For example, the human hearing range extends to approximately 20 kHz, so a digital audio signal must have a sample rate of at least 40 kHz to represent that range.

android audio flinger

In practice, sample rates of For details, refer to Nyquist frequency and Hearing range. Android-Specific Terms Android-specific terms include terms used only in the Android audio framework and generic terms that have special meaning within Android. An audio framework for Linux that has also influenced other systems. For a generic definition, refer audooflinger ALSA. AudioEffect API and implementation framework for output post-processing effects and input pre-processing audiiflinger.

The API is defined at android. AudioFlinger Android sound server implementation.

Audio Terminology

AudioFlinger runs within the mediaserver process. For a generic definition, refer to Sound server. For details, see Managing Audio Focus and the focus-related methods and constants of android.

AudioMixer Module in AudioFlinger responsible for combining multiple tracks and applying attenuation volume and effects. For a generic definition, refer to Audio mixing recorded music discusses a mixer as a hardware device or software application, andfoid than a software module within a system.

AudioRecord Primary low-level client API for receiving data from an audio input device such as a microphone. The data is usually PCM format.

AudioResampler Module in AudioFlinger responsible for sample rate conversion. For details, see audio source. As of API level 21 and above, audio attributes are preferred.

AudioTrack Primary low-level client API for sending xudioflinger to an audio output device such as a speaker. The data is usually in PCM format. However, an AudioFlinger client can be a thread running within the mediaserver system process, such as when playing media decoded by a MediaPlayer object. FastCapture Thread within AudioFlinger that audilflinger audio data to lower latency fast tracks and drives the input device when configured for reduced latency. FastMixer Thread within AudioFlinger that receives and mixes audio data from lower latency fast tracks and drives the primary output device when configured for reduced latency.