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Audio keywords

Digital audio​

  1. Sampling rate

The number of times the audio is sampled during processing. The general values are multiples of 44100 (44.1K) and 48000 (48K).

  1. Voice channel

Supports the number of channels that can produce different sounds. Today's music players are generally dual-channel, and multi-channels are mainly used in the film and television industry. Typical value is 2 for two channels.

  1. Deep

The bit depth is how many bits are used to represent the amplitude at a certain point in time. The more bits the more precise the amplitude change that can be represented. Typical values are the bit depths represented by 16, 24, and 32 are 16 bits, 24 bits, and 32 bits, respectively.

  1. Frequently sounded

Frequency Response (English: Frequency Response, referred to as frequency response) is the response of the measurement system relative to the output end when a signal with constant amplitude and frequency change is input to the electronic instrument system. 维基百科

  1. Phase

Phase is a measure that describes the change of signal waveform. It is usually in unit of degrees (angle), also called phase angle or phase. When the signal waveform changes periodically, the waveform cycles for one week to 360º. Often used in science fields, such as mathematics, physics, electricity, etc. 维基百科

  1. Bit rate

Indicates how many bits of encoded (compressed) audio data need to be represented per second. 比特率

  1. Resampling (SRC, Sample Rate Conversion)

  2. PCM

A method to simulate digital audio. Most audio is now represented in this way. For driver developers, PCM may also be a digital audio interface for PCM. 维基百科

  1. DSD

Another way to simulate digital audio. It has a completely different representation from PCM. Direct Stream Digital (DSD) is a patent belonging to Sony and Philips. It uses pulse-density modulation to encode audio signals to store audio signals on digital media. This technology is used to SACD. 维基百科

  1. D2P（DSD to PCM）

Since the representation methods of DSD and PCM are different, when some devices only support PCM, they need to convert the DSD signal into PCM. This process is the process of D2P. The D2P process involves a lot of processing, so it requires more computing resources, and the CPU usage will also increase when using the CPU to perform this processing.

  1. DoP（DSD over PCM）

Although some devices support DSD playback, since the transmission process (for example: USB Audio\SPDIF) only supports the transmission of PCM signals, DSD signals can be transmitted by borrowing the original PCM signal transmission method, which is called DoP. For example: DoP transmission of USB Audio, DoP transmission of SPDIF. For detailed definition of DoP, please refer to this document "DoP_openStandard_1v1.pdf"

  1. Native

Native in USB Audio scenarios is used as an independent channel for DSD data. Therefore, generally speaking, Native only targets the input and output of USB Audio.

  1. I2S

Drive digital audio interfaces that developers need to know. 维基百科

  1. S/PDIF

S/PDIF (Sony/Philips Digital Interface Format) is a digital audio transmission interface defined by Sony and Philips. 维基百科

  1. Coaxial and fiber optic

On the player, different media are generally transmitted to S/PDIF signals, and in fact, all S/PDIF signals are transmitted. Coaxial and optical fiber are two different transmission media, which may be used in all processes involving signal transmission.

  1. DAC

DAC is the abbreviation of digital analog (Analog) conversion chip.

  1. USB DAC

Devices that support audio input through USB, such as many audio cables, are connected to the phone with a USB interface and then output from 3.5mm or other interfaces. It is generally used to describe audio devices that support the USB Audio In protocol.

  1. EQ (equalizer)

  2. Mqa

MQA is divided into two processes: Decoder and Render, so there are Full Decode players or other devices that support Decoder and Render; there are also Tidal/Xiami APP or digital output devices that only support Decoder, and this output is digital output; there are also devices that only support Render, which must be of the device type. For example: When HiBy R3/R3PRO is a music player, MQA files are played through headphones or balanced ports. At this time, it belongs to Full Decoder (that is, it includes both the Decoder and the Render process). When playing MQA files coaxially as a music player, this time it belongs to Decoder (that is, it only contains the Decoder process). When used as a USB DAC device, the computer plays MQA files and R3/R3PRO receives audio data. At this time, R3/R3PRO belongs to Render (only the Render process)

  1. Mseb

  2. Channel balance

USB​

  1. USB Audio

USB Audio Protocol

  1. USB Mass Storage

USB 大容量存储协议

  1. USB MTP

USB 媒体传输协议

  1. USB HID

  2. USB ADB

USB Android Debug Bridge

Bluetooth​

Bluetooth Profiles https://en.wikipedia.org/wiki/List_of_Bluetooth_profiles

  1. HSP（Headset Profile）

HSP allows Bluetooth devices to control phone calls, such as answering, hanging up, rejecting, voice dialing, etc. Rejecting and voice dialing depends on whether the Bluetooth headset and phone support it.

  1. HFP（Hands-Free-Profile）

In terms of function, it is an extension of HSP. In addition to the above functions, it also includes advanced functions such as controlling three-party calls, incoming call rejection, and incoming caller ID on the headset. However, the implementation method is completely different from the AT CMD used for control. HFP

  1. A2DP

The full name of A2DP is Advanced Audio Distribution Profile (Bluetooth Advanced Audio Transmission Specification)

  1. AVRCP

AVRCP (Audio/Video Remote Control Profile), audio/video remote control specification.

  1. AVDTP

  2. HID

  3. SPP

  4. RFCOMM

  5. L2CAP

  6. GATT

A2DP Codec​

  1. SBC

Bluetooth audio codec, all Bluetooth that supports the A2DP protocol must include the Codec.

  1. AAC

Bluetooth audio codec is mainly used on Apple devices. For example, iOS contains audio encoding outputs of SBC and AAC.

  1. APTX

Bluetooth audio codec developed by Qualcomm.

  1. aptX LL

Bluetooth audio codec, a low-latency audio codec developed by Qualcomm, is mainly used in scenarios such as movies and games that require high latency.

  1. aptX HD

Bluetooth audio codec, a high-quality audio codec developed by Qualcomm, supports up to 48k sampling rate output and can reach a transmission bit rate of 576kbps (48k).

  1. LDAC

Bluetooth audio codec, audio codec developed by Sony, supports up to 96k sampling rate output and can reach a transmission bit rate of up to 990kbps. For details, please refer to the description in Wikipedia. (This encoder has been preset on all Android systems after Android 8.0 (Android Oreo)) LDAC

  1. UAT（Ultra Audio Transmission）

Bluetooth audio codec, audio codec developed by HiBy, supports up to 192k sampling rate output and can reach a transmission bit rate of up to 1.2Mbps.

Other Bluetooth technologies​

  1. cVc noise reduction

CVC is the abbreviation of Clear Voice Capture. It is a software noise reduction technology. Its principle is to suppress various types of reverberation noise through the built-in noise cancellation software and microphone of the headset.

  1. DSP noise reduction

DSP is the abbreviation of digital signal processing. Its working principle is: the microphone collects external ambient noise, and then uses the noise reduction system function inside the headphone to copy and generate a reverse sound wave equal to the external ambient noise, offsetting the noise, thereby achieving better noise reduction effect.

  1. ANC noise reduction

ANC refers to Active Noise Control, which actively reduces noise. The basic principle is that the noise reduction system generates reverse sound waves equal to the external noise and neutralizes the noise.