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PCM [ Pulse Code Modulation ] Pulse Code Modulation

PCM is one of the methods to convert analog signals such as voice into digital data. A sample of signal strength at regular intervals. If you save it as is, it will be uncompressed data.

PCM

The analog signal strength is measured at regular intervals according to the sampling rate and quantized as an integer value within a specific number of bits. For example, audio from a CD is recorded at a 44.1 kHz (kilohertz) sample rate and 16-bit quantization, which measures signals 44,100 times per second and represents their intensity in 65,536 (2 16 ) steps.

Higher quality data can be obtained by increasing the sampling rate and the number of quantization bits, but the amount of data increases accordingly. According to the sampling theorem, signals up to half the sampling frequency can be reproduced, which is called the Nyquist frequency. In the case of speech, it is known that the upper limit of human audible sound is about 20 kHz, and it is said that if a sampling frequency higher than 40 kHz is used, it will be possible to reproduce a near-natural sound from the recorded data.

The normal PCM method is also called linear PCM (LPCM), which is a format in which the data obtained by each sampling is ordered, but the difference registration method In addition, a method for adaptively changing the number of quantization bits of each DPCM sample according to the fluctuation range of the immediately previous sample is called ADPCM (Adaptive Defferential PCM). This is often used in practice because it can reduce the amount of data after encoding while maintaining almost the same quality as PCM.

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DSD or PCM, which format is really better?

DSD PCM

High definition music exists as digital files in two main formats, PCM and DSD. How are they alike, how are they different, and which one should I prefer?

What is PCM
Let’s start with the fact that PCM (Pulse Code Modulation) is initially older, the first mentions of its successful use date back to the middle of the last century and are associated, like many technological advances, with the defense industry, that is, with the Navy radars. As for home use, first of all it is a well-known CD with a sampling frequency of 44.1 kHz and a 16-bit quantization level.

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What is DSD
DSD (Pulse Density Modulation) is a format developed by Sony and Philips at the end of the last century and intended for the digital archiving of analog phonograms. The physical medium of this format is SACD. In fact, there is only one similarity between these two formats, both are digital, which for the user means the possibility of making unlimited copies without loss. As for the difference, relative to the field of graphic design, it is pretty much the same as raster and vector graphics. And if it is even more artistic, like cross stitch and watercolors. In both cases, an image is obtained, but the method of its creation and, as a result of perception, are completely different.

philipsCD100

What is the difference?
PCM, even because of its age, is much more studied, it has much better compatibility with a large number of very different devices, it implies the possibility of editing (equalization, division into frequency bands, transformations). DSD is actually a closed format, you can record to it, you can play it back, that’s all. However, it is inherently much closer to the original analog signal.

Which is better?
The first and most important conclusion is that from a technical point of view, the formats are far apart in terms of implementation methods, but are often practically indistinguishable in practical use, that is, in the sound of the final file. We are talking only about small differences in the nuances of the presentation of the music. So, all things being equal, when choosing the next file to download and play, it’s best to focus on the source material. If you are looking to digitize an analog then DSD will probably be preferable and will retain more nuances from the original. If it is a remastering of a digital recording previously made in PCM, then it would be more logical for it to stay in this domain.