The main difference between PCM and ADPCM is that the Pulse Code Modulation (PCM) is ideal when you require high-quality audio whereas the Adaptive Differential Pulse Code Modulation (ADPCM) is best for storing with less storage space and for long distance transmission.
It is important to understand the difference between PCM and ADPCM before choosing the right format of compression.
Key Areas Covered
ADPCM, Compression, Digital Transmission, PCM
What is PCM
PCM is the short form of Pulse code modulation. With the use of an analog to digital converter, an analog speech waveform can be sampled and converted into a digital code that consists of multibit. The resultant digital code will be stored in the memory and recalled for playback when needed. PCM will sample and quantize the analog signal before it is represented as digital binary form. PCM will also convert the continuous time signal continuous amplitude waveform into discrete time and discrete.
The sampling rate will have to be greater than or equal to the Nyquist rate. This will avoid the effect of aliasing. When a higher frequency is used it will be easier to reconstruct the waveform at the receiver.
What is ADPCM
ADPCM or Adaptive differential pulse code modulation is a modulation technique used to convert an analog signal into its binary form. The conversion takes place by taking frequent samples of the sound and the captured values will be represented in a binary form. This technique is a variation of pulse code modulation. It is used in fiber optic communication, which is usually long-distance lines. Organizations will use this technique through remote sites to broadcast data and voice. The voice signal will be digitized before the broadcast. Telecommunication uses ADPCM in speech compression which helps in reducing the bit flow without any drop in the audio quality. ADPCM can be applied to many waveforms that include images, modern data, and high-quality audio.
Difference Between PCM and ADPCM
In computing, the PCM and ADPCM are subclasses of the Microsoft waveform or .wav file format. PCM will save data in the .wav file using a sampling rate of 8 bits per second. ADPCM will use deltas between samples at 4 bits per second. ADPCM will take up half of the disk space when the number of bits per sample is reduced. This will help in storing longer duration sound files. It will store the value difference between a couple of adjacent PCM samples and makes assumptions to reduce data. Because of this assumption, the ADPCM will properly reproduce low frequencies while high frequencies get distorted. The distortion can be audible with 11 kHz ADPCM files.
Sound can be stored in PCM and ADPCM formats. It is important to understand the difference between PCM and ADPCM before choosing the right format of compression. If the audio quality of the file is important, it will be good to use the PCM format and if the duration is important, it would be a better choice to use the ADPCM format.