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Subband coding resides at the heart of the popular MP3 format (more properly known as MPEG-1 Audio Layer III), for example. Sub-band coding is used in the G.722 codec which uses sub-band adaptive differential pulse code modulation (SB-ADPCM) within a bit rate of 64 kbit/s. In the SB-ADPCM technique, the frequency band is split into two sub ...
The word pulse in the term pulse-code modulation refers to the pulses to be found in the transmission line. This perhaps is a natural consequence of this technique having evolved alongside two analog methods, pulse-width modulation and pulse-position modulation , in which the information to be encoded is represented by discrete signal pulses of ...
These are logarithmic compression systems where a 13- or 14-bit linear PCM sample number is mapped into an 8-bit value. This system is described by international standard G.711 . Where circuit costs are high and loss of voice quality is acceptable, it sometimes makes sense to compress the voice signal even further.
Differential pulse-code modulation (DPCM) is a signal encoder that uses the baseline of pulse-code modulation (PCM) but adds some functionalities based on the prediction of the samples of the signal. The input can be an analog signal or a digital signal .
Adaptive differential pulse-code modulation (ADPCM) aptX / aptX-HD: aptX 1989 Unknown Unknown [28] Digital Theater Systems: DTS 1990 8% 6% [29] [30] Master Quality Authenticated: MQA 2014 Unknown Unknown Sub-band coding (SBC) MPEG-1 Audio Layer II: MP2 1993 Unknown Unknown [31] Musepack: MPC 1997 SBC: SBC 2003 Unknown Unknown [32]
Pulse-density modulation, or PDM, is a form of modulation used to represent an analog signal with a binary signal.In a PDM signal, specific amplitude values are not encoded into codewords of pulses of different weight as they would be in pulse-code modulation (PCM); rather, the relative density of the pulses corresponds to the analog signal's amplitude.
The binary signal is encoded using rectangular pulse-amplitude modulation with polar NRZ(L), or polar non-return-to-zero-level code. In telecommunications, a non-return-to-zero (NRZ) line code is a binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usually a negative voltage, with ...
where is the number of bits in a quantized sample, and is the signal power calculated above. Note that for each bit added to a sample, the SQNR goes up by approximately 6 dB ( 20 × l o g 10 ( 2 ) {\displaystyle 20\times log_{10}(2)} ).