# Understanding CODECs

## Overview

This article aims to highlight the key differences between codecs. This article has been written to be easily digestible, and easy to search.

## Common Codecs

These Codecs are commonly used by Crazytel.

### PCMA | G.711a:

* A-law: A common audio coding standard used primarily in Europe and other parts of the world.

* High quality: Provides good audio quality but has a high bandwidth requirement (64 kbps (dial-up speed)).

### Opus:

* Modern and versatile: A modern, flexible audio codec designed for a wide range of applications, including voice, music, and video conferencing. 

* High quality and efficiency: Offers excellent audio quality at various bitrates, making it suitable for different network conditions.

### T.38:

* Fax over IP: Another standard for fax over IP, often considered more robust and reliable than H.232.

## Uncommon Codecs

Although Crazytel won't block transmissions using these protocols, we don't recommend using them.

### PCMU | G.711µ:

* µ-law: Another common audio coding standard, primarily used in North America and Japan. 

* High quality: Similar to PCMA in terms of audio quality and bandwidth usage.

### G729:

* Low-bitrate: Designed for low-bandwidth networks, offering good voice quality at a much lower bitrate (8 kbps) than G.711.

* Popular for VoIP: Widely used in VoIP systems due to its efficient bandwidth usage. 

### H.232:

* Fax over IP: A standard for transmitting fax signals over IP networks.

* **Not an audio codec:** Specifically designed for fax communication.