Basic Processing of Audio Media

- Sep 05, 2018-

The basic audio digitization process includes the following:

Transformation and conversion between different sampling rates, frequencies, and channel numbers. The transformation is simply treated as another format, and the conversion is done by resampling, where an interpolation algorithm can also be employed as needed to compensate for the distortion.

Various transformations for the audio data itself, such as fade in, fade out, volume adjustment, and the like.

Transformations made by digital filtering algorithms, such as high-pass, low-pass filters.

3D processing of audio media

For a long time, computer researchers have been underestimating the role of sound in human information processing. When virtual technology continues to evolve, people no longer meet the sound of monotonous planes, but rather a three-dimensional sound effect with a sense of space. The auditory channel can work simultaneously with the visual channel, so the three-dimensional processing of the sound can not only express the spatial information of the sound, but also combine with the multi-channel of visual information to create an extremely realistic virtual space, which is very important in the future multimedia system. This is also an important measure in media processing.

The most basic theory of human perception of the location of sound sources is the duplex theory, which is based on two factors: the difference in the arrival time of the sound between the ears and the difference in the intensity of the sound between the ears. The time difference is caused by the distance. When the sound is transmitted from the front and the distance is equal, there is no time difference, but if it is three degrees to the right, the time to reach the right ear is about 30 microseconds less than the left ear. Thirty microseconds allowed us to identify the location of the sound source. The difference in intensity is caused by the attenuation of the signal. The attenuation of the signal is naturally caused by the distance, or the occlusion of the human head causes the sound to attenuate, resulting in a difference in intensity, which is heard near the ear on the side of the sound source. The sound intensity is greater than the other ear.

Based on the duplex theory, as well, by mixing a common two-channel audio between two channels, the ordinary two-channel sound can be made to have a three-dimensional sound field effect. This involves the following two concepts about the sound field: the width and depth of the sound field.

The width of the sound field is done using the principle of time difference. Since the normal stereo audio is now expanded, the position of the sound source is always in the middle of the sound field, which simplifies our work. All that is to be processed is to mix the sounds of the two channels with appropriate delay and intensity. Because of this limitation, there is a limit, that is, the delay cannot be too long, and otherwise it will become an echo.

 

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