[Audio and Video Media Production Basics] audio processing preliminary audio

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I. Digital Processing of audio media

With the development of computer technology, especially the implementation of massive storage devices and large-capacity PCs, it is possible to digitize audio media. The core of digital processing is the sampling of Audio Information. by processing the collected samples to achieve various effects, this is the basic meaning of digital processing of audio media.

Ii. Basic audio media processing

Basic digital audio processing includes the following types:

Conversion between different sampling rates, frequencies, and channels. Here, the transformation simply regards it as another format, and the conversion is carried out through re-sampling. interpolation algorithms can also be used as needed to compensate for distortion.

Various changes made to the audio data, such as fade-in, fade-out, and volume adjustment.

Transform using digital filtering algorithms, such as high-pass and low-pass filters.

Iii. 3D processing of audio media

For a long time, computer researchers have underestimated the role of voice in information processing. As virtual technology continues to develop, people will no longer be satisfied with monotonous plane sounds, but will be more eager for three-dimensional sound effects with a sense of space. The auditory channel can work with the visual channel at the same time. Therefore, the three-dimensional processing of sound can not only express the spatial information of sound, but also create extremely realistic virtual space by combining with the multi-channel visual information, this will be extremely important in the future multimedia systems. This is also an important measure in media processing.

The most basic theory of human perception of the location of the sound source is the duplex theory, which is based on two factors: the arrival time difference of the two ears and the intensity difference of the two ears. The time difference is caused by the distance. When the sound is sent from the front, the distance is equal, so there is no time difference. However, if the right is three degrees, the time to reach the right ear is about thirty microseconds less than the left ear, these thirty microseconds allow us to identify the location of the sound source. The intensity difference is caused by signal attenuation. The signal attenuation is caused by natural distance or human head occlusion, resulting in sound attenuation, resulting in a difference in intensity, so that the intensity of the sound heard by the ears close to the sound source side is greater than that of the other ear.

Based on the duplex theory, as long as a common dual-channel audio is mixed between two channels, the normal dual-channel sound can sound like a three-dimensional sound field. This involves two concepts related to the sound field: the width and depth of the sound field.

The width of the audio field is completed based on the time difference principle. Because the common stereo audio frequency is expanded, the position of the audio source remains unchanged in the middle of the audio field, this simplifies our work. The only thing we need to do is to mix the sound of two channels after the proper delay and strength are weakened. Because such expansion has limitations, that is, the delay cannot be too long, otherwise it will become an echo.

The depth of the sound field is achieved by the principle of intensity difference. The specific manifestation is Echo. the deeper the sound field, the longer the echo latency. therefore, the echo setting should provide at least three parameters: the echo attenuation rate, the echo depth, and the latency between the echo. At the same time, you should also provide the option to set the depth of sound mixed by another channel.


Initial audio processing