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DSD

1. DSD History​

The origin of DSD has actually been a long time ago. As early as the 1960s, it was already using pulse density modulation (PDM) encoding to record audio signals on digital media. Strictly speaking, it should be implemented by a special branch of PDM - Pulse Width Modulation (PWM). This encoding method has been completely replaced by the PDM format.

Common DSD encodings are now based on the PDM specification. The specification for this music encoding format was published in 1999 and was developed by Sony, the giant leading music storage format at that time, and Philips. As for the reasons for developing the DSD specification, it is a bit complicated. It is mainly because the CD specification patents formulated by Sony and Philips were about to expire at that time. With the loss of CD patents coming to a large amount of benefits, Sony and Philips decided to join forces to create the next generation of music storage specifications Super Audio Compact Disc (SACD), so most of the emergence of DSD was due to commercial reasons.

2. DSD keywords​

1、Native(RAW)​

DSD original stream (bare data) is output directly.

advantage

  • The original DSD code stream output is completely handed over to the hardware for corresponding digital-to-analog conversion;

shortcoming

  • The standards need to be redefined because there is no unified standard, and there may be certain differences in the definitions of different manufacturers;

2、DoP​

DoPThe full name is DSD Over PCM, which means that DSD is transmitted through the PCM channel. Because before DSD was commercialized, the audio transmission standards on the market were defined based on PCM format, in order to directly use these existing audio transmission standards, DoP was born, so that DSD data can be directly transmitted without modifying the existing audio transmission standards.

The specific operation method is to DoP encapsulate the DSD data before transmission, restore the DSD data encapsulated into DoP after receiving the data, and then playback the DSD data using the DSD data.

advantage

  • Directly utilize existing audio transmission standards without redefining the standards

  • Reduce development costs and directly encapsulate DSD data into DoP data packets

shortcoming

  • The DoP identification head occupies bandwidth, reducing the effective data that can be transmitted

3、D2P​

The full name of D2P is DSD to PCM, which means DSD to PCM in Chinese. In fact, it is to convert the DSD data stream into a PCM data stream through certain filtering operations, so that DSD can be played directly on the original audio device based on PCM definition.

This method requires a lot of computing because there is a conversion between two different signal formats, which results in the process of doing this action that requires a lot of computing resources (for most platforms, it is a high CPU occupancy rate).

advantage

  • Directly utilize existing audio transmission standards without redefining the standards

  • Reduce development costs and transcode DSD data into PCM data

shortcoming

  • The process of DSD to PCM requires a lot of computing and has certain requirements for the computing capabilities of the device.

  • There is a process of DSD to PCM, so this process will have certain losses to sound quality.

III. DSD application​

1、 DSD via DAC​

Native

  • DSD Clock (DSDCLK)
  • DSD left channel (DSDA)
  • DSD Right Channel (DSDB)

D2P

2、DSD via USB​

  • DoP

  • Native

  • D2P

3、DSD via S/PDIF​

  • DoP

  • D2P

4、DSD via Bluetooth​

  • D2P

##References:

WiKiPedia DSD

DSD vs. PCM: Myth vs. Truth

揭開 DSD 的神秘面紗：數位音訊編碼之爭 DSD vs. PCM