Codecs are computer programs for encoding or decoding digital data stream or signal. The codec encodes a data stream or signal for transmission and storage, also in encrypted form, and the decoder function reverses the encoding for playback or editing. Codecs are used in video conferencing, streaming media and video editing applications.
In the middle of the 20th century, the codec was a device that coded analog signals in digital form using pulse modulation (PCM). Later, the name was also applied to software which was used for conversion between digital signal formats, including the compressor function.
The word modem comes from the combination of two words modulator-demodulator. The telecommunications industry refers to the device as a data set. It converts digital data from computers to analog signals for transmission over telephone lines. On the receiving side, the analog signal is converted back to digital data.
The audio codec converts analog audio signals to digital signals for transmission or codes them for storage. The receiving device processes digital signals back to the analog form using an audio decoder for playback. An example of this are the codecs used in the sound cards of personal computers. The video codec performs the same task for video signals.
In addition to coding the signal, the codec can compress data to reduce transmission bandwidth or disk space. Among the codecs that compress the signal, we distinguish compression codecs that are lossy and lossless. Most popular codecs are lossy, reducing the quality of the signal, but also the size of the resulting file.
The codecs use two techniques: PCM (pulse-code modulation) and delta modulation. There are many different codecs, both free and paid. Among them, we find codecs with low and high bitrates (number of bits per unit of time).