#g711

Mira la nota http://www.servervoip.com/blog/codecs-y-formatos-de-audio-en-telefonia-ip/

Codecs y Formatos de audio en Telefonia IP

Mira la nota http://www.servervoip.com/blog/que-codecs-usa-tu-equipo/

¿Qué codecs usa tu equipo?

Mean Opinion Score (MOS)

Mean Opinion Score (MOS) is a test used in telephony networks to obtain a human user's perspective of call quality in a particular network. Customers can obtain MOS scores for their networks by visiting: Will my internet connection and network support high quality VoIP calls?

MOS Score Summary Reference:

1 - Unsatisfactory - Very annoying distortion which is objectionable

2 - Poor - Annoying distortion but not objectionable

3 - Fair - Perceptible distortion that is slightly annoying

4 - Good - Slight perceptible level of distortion but not annoying

5 - Excellent - Imperceptible level of distortion

What Customers should expect:

A MOS score of 4 is very optimal for a G711 codec call, which is a standard codec, and is comparable to Toll quality. A score of 5 is a rare occurrence and not receiving scores in the range of 5 is not a disqualifier for a high quality voice experience, as well as VoIP in general.

I implemeted g711 for audio companding in erlang programming language.

Quote from wiki:

G.711 is an ITU-T standard for audio companding. It is primarily used in telephony. The standard was released for usage in 1972. Its formal name is Pulse code modulation (PCM) of voice frequencies. It is required standard in many technologies, for example in H.320 and H.323 specifications. It can also be used for fax communication over IP networks (as defined in T.38 specification). G.711, also known as Pulse Code Modulation (PCM), is a very commonly used waveform codec. G.711 uses a sampling rate of 8,000 samples per second, with the tolerance on that rate 50 parts per million (ppm). Non-uniform (logarithmic) quantization with 8 bits is used to represent each sample, resulting in a 64 kbit/s bit rate. There are two slightly different versions; μ-law, which is used primarily in North America, and A-law, which is in use in most other countries outside North America.