What is a Codec?
0A codec is software or a device that compresses, decompresses, and converts analog and digital signals for transmission over a network. This speeds up the transmission and download time, as without them, high quality sound and video would take much longer to send and receive.
Audio and video codecs can be divided into two categories; Lossless and lossy compression.
The audio and/ or video is compressed and decompressed without any loss of quality.
Some data is lost during the compression and decompression process, evidenced by pixelation of the video, and is most often used with a lower bandwidth internet connection.
Common Audio Codecs
GSM – 13Kbps (Full Rate), 20ms frame size.
GSM has a high compression ratio, and is available in many software and hardware platforms. GSM encoding was used in mobile phones before 3G and 4G became available.
iLBC – Internet Low Bit Rate Codec – 15Kbps, 20ms frame size | 13.3Kbps, 30ms frame size
iLBC is free since being acquired by Google. iLBC is used by many VoIP applications as it is tough against packet loss.
ITU G.711 – 64Kbps, requires at least 128Kbps for two-way.
ITU G.711 is one of the oldest codecs (created in 1972), and is best used in LANs. This codec has very low processor requirements, and delivers very high quality of speech.
ITU G.719 – 32/48/64/128 Kbps, 28ms frame size.
ITU G.719 provides high quality voice transmission with a moderate bit rate at a low computational load. This codec combines elements of codecs produced by Polycom and Ericsson that have been used in videoconferencing systems for many years.
ITU G.722 – 48/56/64 Kbps
ITU G.722 is often able to produce better voice quality than PSTN, as it captures a range of frequencies twice as large as G.711. This codec is able to adapt to varying compressions and conserves bandwidth for network congestion.
ITU G.723.1 – 5.3/6.3Kbps, 30ms frame size.
G723.1 can be used with dial-up and on low bandwidth networks as it works with a very low bit rate. Despite this, this codec offers high compression with high quality audio, the potential downside being the requirement of more processor power.
ITU G.726 – 16/24/32/40Kbps
This codec is an improved version of G.271 and G.723.
ITU G.728 – 16Kbps
G.728 is used in digital transmission systems, coding analog into digital signals.
ITU G.729 – 8Kbps, 10ms frame size.
G.729 is great with bandwidth usage and forgiving of errors. This codec is a marked improvement over others however no free option is available. Licensing for this codec is included in hardware costs of phone systems and gateways that implement it.
Speex – 2.15 to 44.2 Kbps.
Speex is one of the most preferred in many VoIP applications, as its variable bit rate minimises bandwidth usage.
LPC10 – 2.5 Kbps.
LPC10 carries voice data in a narrow band of frequencies, offering a clear but often “robotic” sound.
DoD CELP – 4.8 Kbps.
DoD CELP is a low bit rate speech coding algorithm, providing significantly better quality than other low bit-rate algorithms of its time.
Common Video Codecs
The Vp8 codec is free for use, and is used for encoding and decoding high definition video. It can be used for video either in a file format or a bit-stream for viewing online.
This codec is currently one of the most used formats for recording, compression and playback of high definition video.