Pioneer VSX-D557 Operating Instructions - Page 35

OTHER ❑olby ❑igital (AC-3) Dolby Digital (AC-3) is the name of the Dolby surround multi-channel digital system that was developed after the Dolby Surround System and Dolby Pro Logic Surround System. 5.1 channel digital surround track 4 channel analog sound track (Matrix) AC-3 encoding AC-3 for movie films The number of movies made using Dolby Digital since 1992 has exceeded 300 and continues to increase. For compact disc players and laser disc digital sounds, 16 bits are used to sample the original analog audio waveform and sampling is carried out 44,100 times every second. However because an enormous amount of recording signal data is required for the multi channel system with this method, Dolby Digital (AC-3) is used to compress the data. In reproducing audio signals, the smaller the bit number used, the lower the sound quality. With Dolby Digital (AC3), any drop in auditory sound quality is prevented by using masking technology and digital filtering technology based on personal auditory characteristics. ■ Laser disc format Laser discs are now available on the market in large numbers. This means that the recording of different format audio signals on the laser disc raises the important question of compatibility with existing laser discs. Dolby Digital (AC-3) records signals using one analog audio channel to maintain this compatibility with existing discs and players. As shown in the following figure, the digital audio sounds of Dolby Digital (AC-3) discs can be played back as currently done. Analog sounds are played back by using the other channel without the Dolby Digital (AC-3) signals for monaural audio signals. Analog sound Dolby Digital (Monaural) (AC-3) sound (Monaural) Digital sound Video 2 i 4 8 14 12 14 MHz Frequency ■ Comparison with Dolby Pro Logic Surround Dolby Digital (AC-3) is also known as the 5.1 channel system. It is equipped with 5 channels (front left, front right, center, rear left, rear right) in the frequency range from Lia 20 Hz to 20 kHz and an independent sub woofer channel. The sub woofer channel is also called LFE (Low Frequency Effect). The LFE channel can be used as desired to enjoy strong 0 bass sounds. The following table shows the comparison with Dolby Pro Logic Surround effects. No. of recording channels No. of playback channels Playback channel structure Sound processing Rear (Surround) high frequency playback limit Other Dolby Digital (AC-3) 5.1 channels (Max.) 5.1 channels (Max.) Front left, front right, center, rear left, rear right, sub woofer Digital discrete processing 20,000 Hz • 5.1 channel is completely independent • High dynamic range • Stable position, high phase characteristics, and advanced surround effects reproduction Dolby Pro Logic Surround 2 channels 4 channels Front left, front right, center, rear Analog matrix processing 7,000 Hz _I 35