What does Dolby often see at the beginning of the film mean? Where did it come from?

I often meet friends and ask: Now there are Dolby amplifiers, Dolby DVDs, Dolby story discs and even Dolby movies. What is Dolby?

It's simple: Dolby is the Chinese translation of Dr. R.M. Dolby in Britain. Dolby Lab, which he set up in the United States, has successively invented Dolby noise reduction system, Dolby surround system and many other technologies, which have had a great impact on film acoustics and home acoustics. I think the meaning of the above question should be: what is Dolby technology?

Dolby technology often used in families mainly includes Dolby noise reduction system and Dolby surround system.

Dolby noise reduction system is mainly used to reduce the noise during recording or playback. In the 1970s, it was widely used in home tape recorders. At that time, we often found symbols on many tape recorders and original music tapes, indicating that the machine had Dolby noise reduction function, and the tape was recorded by Dolby noise reduction. Of course, this kind of recording tape can only be played in a tape recorder with Dolby noise reduction system to achieve satisfactory noise reduction effect.

Dolby surround system is a cinema sound system successfully developed by Dolby Laboratories in the United States to improve stereo quality. In the stereoscopic cinema, in order to create an immersive sense of space for the audience, in addition to the left and right channels, there is also a central channel that can enhance the sound effect on the screen and a surround channel that allows the audience to feel the environmental atmosphere and special effects. This surround sound channel uses many speakers and stands parallel to the two side walls and the back wall. Because the direct recording and transmission of multi-channels is expensive and inconvenient, 1976, Dolby Laboratories invented Dolby Stereo Film System, which denoised the information of left, middle, right and surround channels and compiled and recorded them into two channels in a certain way. When playing, it reverts to four channels in the opposite way (that is, 4-2-4 mode), thus realizing the compatible transmission of multi-channel and two-channel. In Star Wars filmed in the late 1970s, Dolby surround system successfully realized the synchronization of sound direction and picture movement, which made the audience feel the sense of orientation and scene when the sound whizzed overhead, causing a shock in the film industry. Therefore, the system is widely used in cinemas.

In order to make ordinary families enjoy similar effects to cinemas, Dolby Laboratories has simplified and concentrated the Dolby stereo film system, and successively introduced Dolby surround sound system and Dolby directional logic surround sound system. Now we often talk about Dolby power amplifier, mostly referring to AV power amplifier with Dolby directional logic surround sound decoder and certified by Dolby Lab.

Dolby Pro-Logic Surround is the second generation home audio-visual surround sound system, which is an improvement of the first generation dolby surround system. Published in 1987. Since the late 1980s, it has been widely used to record the sound effects of video programs such as video recorders, LD and VCD. Of course, its decoding system naturally settled in the AV amplifier. The system has four channels: left, right, center and surround, and adopts a specially designed directional enhancement circuit, which can adjust the relative strength of each channel according to the actual situation of the program signal, thus greatly enhancing the sense of audio-visual positioning, direction, movement and the reproduction ability of the original sound field, and truly realizing the "cinema" effect in the family. As a result, Dolby amplifier has become the first choice for people to form a home theater. Of course, only discs equipped with Dolby directional logic surround sound and Dolby power amplifier can achieve the desired effect.

Although Dolby directional logic surround sound has reached a high 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 the next generation TV broadcasting, Dolby Laboratories and Japanese Pioneer Company released a brand-new digital multi-channel audio system: Audio Coding-3, named AC-3, and 1997 was renamed dolby digital. It can be equipped not only in cinemas, but also in home cinemas.

Dolby AC-3 is a compression/decompression system. It adopts advanced digital compression technology and Dolby's unique special technology, and compresses and codes completely independent six channels (5. 1 channel) of left, right, middle, left surround, right surround and subwoofer into two channels, and records them on film or DVD. When playing, it is restored to six channels by the decoder for playing. In order to achieve the goals of wide dynamic range, high signal-to-noise ratio, high resolution and signal fidelity, each channel is recorded completely independently first, and then compressed and encoded. In compression, Dolby Laboratories uses the basic principle of sound psychology to keep quiet when there is no signal, and when there is audio signal, it uses strong signal to cover up the noise within the hearing range, and deletes the signal part that human ears can't hear or the signal part with similar frequency but low volume but can be ignored. This greatly reduces the content to be processed. AC-3 has achieved high digital audio compression efficiency, but it still gives people a very complete and realistic feeling.

AC-3 system is compatible with Dolby directional logic surround sound system, and the effect is better than THX. Dolby AC-3 should be the mainstream system of home theater in the future.