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Digital Representation
Published in Eddy B. Brixen, Audio Metering, 2020
By adding random noise, the next significant bit (in this case bit no. 17) becomes significant in that, along with the random noise, bit 16 has an average value that is more accurate than achieved by simple truncation. The disadvantage is that the signal-to-noise ratio is impaired. However, this is improved by introducing noise shaping; shaping the noise spectrum, so it leaves the main energy of the noise in a frequency range that is less audible but still reduces distortion. Typically, the noise is moved to the 10–20 kHz region. The result: Less distortion and the added noise is moved out of the audible range (unless played with extraordinary gain). For example, when using a PA system, the premise of noise-shaped dither is a noise floor close to the threshold of hearing. This premise is no longer valid.
Step V
Published in Evren Göknar, Major Label Mastering, 2020
In order to generate the master, the raw mastered files must be rendered to the chosen final resolution. This almost always involves dither if rendering from a high-resolution mastered file (32bit floating-point, 32bit, or 24bit) down to 16bit for a Red Book master. Dither is a type of noise that alleviates quantization error when a file is being rendered to 16bit from a higher bit resolution. Dither often includes simultaneous noise shaping options that psychoacoustically shift quantization noise away from the audio band or oversample and filter the quantization noise to minimize it.3 Additionally, 24bit dither can be used at the output stage of a DAW with an internal processing resolution of 32bit or 64bit to ensure that there is no truncation of the digital word. The term burn refers to making a PMCD in a CD burner; a DDP Master is much more common in this era, and most replicating facilities have a DAW connected to the glass mastering4 setup so that a PMCD will likely be converted to DDP for the glass mastering process.
Audio Codecs
Published in Francis F. Li, Trevor J. Cox, Digital Signal Processing in Audio and Acoustical Engineering, 2019
Following a sigma-delta modulation loop is a decimation stage. The decimation reduces the sample rate by combining the successive 1-bit data. Noise shaping is a filtering process that shapes the spectral energy of quantization error, typically to either de-emphasise frequencies to which the ear is most sensitive, or separate the signal and noise bands completely. If dither is used, its final spectrum depends on whether it is added inside or outside the feedback loop of the noise shaper: if inside, the dither is treated as part of the error signal and shaped along with actual quantization error; if outside, the dither is treated as part of the original signal and linearises quantization without being shaped itself. In this case, the final noise floor is the sum of the flat dither spectrum and the shaped quantization noise. While real-world noise shaping usually includes in-loop dithering, it is also possible to use it without adding dither at all, in which case the usual harmonic-distortion effects still appear at low signal levels.
A SILK Adaptive Steganographic Scheme Based on Minimizing Distortion in Pitch Domain
Published in IETE Technical Review, 2021
Yanzhen Ren, Shan Zhong, Weiping Tu, Hanyi Yang, Lina Wang
As a speech codec for real-time voice communication, SILK can achieve high coding efficiency and adapt to a wide range of applications and environments. An overview of the core encoder Figure 1 is given. It can be simply divided into three parts: adaptive high-pass filter, prediction, and noise shaping. High-pass filter can remove the lowest part of the spectrum that contains little speech energy and background noise. Prediction part is based on linear predictive coding, which provides highly accurate estimates of speech parameters. Noise shaping alters the spectral shape of noise to obtain a perceptually higher quality at the same bitrate. In various applications and environments, SILK speech codec can deliver high speech quality at a given bitrate.