sony sacd 读取原理

sony sacd 读取原理
Sony SACD (Super Audio CD) is a high-resolution audio format that was developed by Sony and Philips in the late 1990s. It was introduced as a successor to the conventional CD format and aimed to provide improved audio quality and a higher resolution sound. The SACD format was designed to be backward compatible with existing CD players, allowing consumers to play both SACD and CD discs on the same player.
The original idea behind SACD was to create a format that could reproduce audio signals that are closer to the original studio recording. To achieve this, several technical advancements were made in the SACD format compared to the traditional CD format.
One of the key features of SACD is its use of Direct Stream Digital (DSD) encoding. The DSD format uses a 1-bit sigma-delta modulation technique to convert the analog audio signals into a digital format. This differs from the Pulse Code Modulation (PCM) used in CDs, which samples the analog audio signals at a specific bit depth and sample rate.
In the DSD encoding used in SACDs, audio signals are sampled at an extremely high rate of 2.8224 MHz, which is 64 times the sample rate of CDs. This high sampling rate allows for capturing more detail and nuance
in the audio signals, resulting in a more faithful representation of the original sound. The 1-bit DSD samples are stored in a digital format on the SACD disc.
To read the DSD samples from the SACD disc, a specialized laser pickup system is used in SACD players. This pickup system is capable of detecting the much narrower track pitch used in SACDs compared to CDs and can read the 1-bit DSD samples accurately.
The laser beam emitted by the pickup system focuses on the spiral track of the SACD disc, which contains the DSD samples. The reflected laser beam is then converted into an electrical signal using a photodiode. This electrical signal is further processed by a series of analog and digital circuits to extract the audio information from the DSD samples.
SACD players also employ a process called Direct Stream Transfer (DST) to compress the DSD audio data on the disc. DST is a lossless compression algorithm that reduces the size of the audio data without any loss of quality. This compression allows more audio data to be stored on the SACD disc, enabling longer playing times compared to conventional CDs.
The SACD format also includes the option to include a separate layer on the disc that contains a standard CD format copy of the audio content. This dual-layer approach ensures backward compatibility, allowing SACD discs to be played on existing CD players.
In summary, the Sony SACD format utilizes the Direct Stream Digital (DSD) encoding technique to capture and store high-resolution audio signals on the disc. A specialized laser pickup system with a narrower track pitch is used in SACD players to read the DSD samples accurately. The DSD samples are converted into an electrical signal, processed, and played back to recreate the original sound. The SACD format also includes DST compression and backward compatibility with CD players to enhance the overall playback experience.。