Pcm eq drc audio processing

PCM

The abbreviation of Pulse-code modulation. (I2S is only a branch of PCM, and the interface definition is the same. The sampling frequency of I2S is generally 44.1khz and 48 khz, And the PCM sampling frequency is generally 8 kHz and 16 kHz. There are four groups of signals: Bit Clock signals, synchronous signals, data input, and data output .)

Two important indicators of PCM signal are sampling frequency and quantization accuracy. Currently, the sampling frequency of CD audio is usually 44100Hz, and the quantization precision is 16 bit.

Two main functions are implemented:

 

• How does playback convert PCM data sent by user space applications into analog audio that can be recognized by human ears?
• Capture is an application that collects and quantifies mic analog signals, converts them to PCM signals, and sends them back to the user space.

 

EQ

 

EQ is the full name of Iser. Its basic function is to adjust the tone by gain or attenuation of one or more audio frequencies. EQ usually includes the following three parameters:

Frequency, frequency-this is a parameter used to set the frequency point you want to adjust;

Gain, gain-the parameter used to adjust the gain or attenuation on the F value you set; quantize, bandwidth ratio-this parameter is used to set the "width" of the frequency band for gain or attenuation. The smaller the Q value, the wider the processing frequency. Application Description: There are two common types of music balancer: graphic equalizer and parametric equalizer ). The graph balancer is a type of 20 ~ full audio according to certain rules ~ 20000Hz is divided into several frequency bands. Each frequency band corresponds to a regulator that can gain or degrade the level, separate the gain or attenuation of the input audio signal according to the specific frequency band. The parameter balancer does not divide fixed bands. It can control any frequency point (including all points within the specified frequency bandwidth near the frequency point) by adjusting the bandwidth, this makes the adjustment control accurate (small bandwidth), fuzzy (large bandwidth), and flexible. The operation control of the parameter balancer is not intuitive, and is mostly used in the professional scenarios of precise sound control. However, audio players such as Winamp and foobar mostly use graphical balancers. A graphic panel with a regulator allows users to easily adjust specific frequencies. Signal morphology angle Description: The equalizer can be divided into two types: Time Domain balancer and frequency domain balancer. The Time Domain balancer changes the tone by adding a series of filters to the time domain audio signal. Most of the time domain balancers are used for traditional audio devices and many music playing software. A time-domain balancer is usually composed of a series of secondary IIR filters or FIR filters in series. Each band corresponds to a filter, and each filter can be individually adjusted and connected together to form the final effect. However, the traditional IIR filter has a feedback loop, which causes phase deviation, while the FIR Filter causes a relatively large time delay. In addition, if you use an IIR or FIR filter, the more band in the balancer, the larger the number of filters to be connected, and the larger the computing workload. The frequency-domain balancer directly performs gain or attenuation on audio signals of a specified frequency in the frequency domain to change the tone. The frequency domain balancer has no phase error and time delay, and is not fixed in the band. It can be used to adjust any frequency. In particular, quick Fourier transformation can be used for faster computation, and even multi-segment balancers won't increase the amount of computing.

DRC

Dynamic Range control (DRC) dynamic range control provides compression and amplification capabilities to make the sound more soft or larger, that is, a signal amplitude adjustment method.

 

Pcm eq drc audio processing