What's the matter with Dolby

Dolby is the Chinese translation of Dr. RM DOLBY in the United Kingdom. He established the Dolby laboratory in the United States and has invented many technologies such as the Dolby noise reduction system and the Dolby surround sound system, which have produced a huge impact on movie sound and home audio. influences.
What is Dolby technology.
Dolby technologies commonly used in homes mainly include Dolby noise reduction systems and Dolby surround sound systems.
Dolby noise reduction system is mainly used to reduce the noise of recording or playback. It has been widely used in home recorders in the 1970s. At that time, we often found many recorders and symbols marked on original music tapes, which means that the machine has Dolby noise reduction function, and the tape uses Dolby. Recorded with noise reduction. Of course, this type of recording tape can only achieve satisfactory noise reduction effects when played in a recorder with a Dolby noise reduction system.
Dolby Surround Sound System is a theater sound system developed by Dolby Laboratories in the United States to improve the quality of stereo sound. In a stereo movie theater, in order to create an immersive spatial feeling for the audience, in addition to the left and right channels, a center channel that enhances the sound effect on the screen and a surround that enables the audience to get the feeling of ambient atmosphere and special effects Channel. This surround channel uses many speakers, which are erected in parallel along the side walls and the rear wall. Because multi-channel direct recording and transmission are expensive and inconvenient, in 1976, Dolby Laboratories invented the Dolby Stereo Film System, which reduces the noise of the left, center, right, and surround channels in a certain way after noise reduction. The compilation is recorded in two channels. During playback, it is restored to four channels in the opposite way (that is, 4-2-4 mode), thus achieving compatible transmission of multi-channel and two-channel. In the "Star Wars" filmed by the Dolby surround sound system in the late 1970s, the direction of the sound and the movement of the picture were successfully synchronized, allowing the audience to feel the sense of orientation and presence of the sound roaring overhead, which caused the film industry Vibration, so this system was later widely used in movie theaters.
In order to enjoy the effect similar to that of movie theaters in ordinary homes, Dolby Laboratories simplified and condensed the "Dolby Stereo Film System", and successively launched the "Dolby Surround Sound System" and "Dolby Pro Logic Surround". Acoustic system ". Now we often say that Dolby amplifiers mostly refer to AV amplifiers with "Dolby Pro Logic Surround Sound" decoders and certified by Dolby Laboratories.
Dolby Pro Logic Surround (DOLBY Pro-Logic Surround) is a second-generation home audio-visual surround sound system that improves on the first generation "Dolby Surround System" and was released in 1987. From the late 1980s to the present, it has been widely used in the recording of sound effects of video programs such as video recorders, LDs, VCDs, etc. Of course, its decoding system has naturally settled in AV amplifiers. The system has four channels of left, right, center, and surround, and uses a specially designed directional enhancement circuit, which can make ingenious adjustments to the relative strength of each channel according to the actual situation of the program signal. The reproduction ability of sound image localization sense, direction sense, movement sense and the original appearance of the sound field is greatly enhanced, and the “theater” effect in the home is truly realized. As a result, Dolby Amplifier became the first choice for people to build home theaters. Of course, a disc with Dolby Pro Logic surround sound must be combined with a Dolby amplifier to achieve the desired effect.
Although Dolby Pro Logic surround sound has reached a higher level in performance, it still cannot get rid of the limitations of analog technology. With the maturity of digital technology, in order to meet the requirements of next-generation TV broadcasting, on the basis of Dolby Pro Logic Surround Sound, in 1994, Dolby Laboratories and Japan Pioneer Company released a new type of digitalization developed in collaboration Multi-channel film and sound system: Audio Coding-3, named AC-3 before its name, and renamed Dolby Digital in 1997: DOLBY DIGITAL. It can be equipped to a movie theater or configured into a home theater.
Dolby AC-3 is a compression / decompression system. It uses advanced digital compression technology and applies Dolby's original special technology to compress and encode six channels (5.1 channels) of completely independent left, right, center, left surround, right surround and subwoofer into two Soundtrack, recorded on film or video disc. During playback, the decoder is restored to six channels for playback. In order to achieve the purposes of wide dynamic range, high signal-to-noise ratio, high separation, and fidelity of the signal, each channel is recorded in a completely independent way, and then compressed and encoded. When compressing, Dolby Laboratories uses the basic principles of acoustic psychology to keep it quiet when there is no signal, and when there is an audio signal, it uses a stronger signal to mask noise in the auditory range and remove what is not heard by the human ear The part of the signal whose frequency or frequency is similar but the volume is low and can be ignored. In this way, the content that needs to be processed is greatly reduced, and AC-3 achieves a higher digital audio compression efficiency, but still can give people a very complete and realistic effect.
The AC-3 system is compatible with Dolby Pro Logic Surround Sound System, and its effect is more superior than THX. The future home theater should be Dolby AC-3 as the mainstream system.