Presentation on theme: "RMAUG Professional Development Series 2/11/09 Dwight Reifsnyder."— Presentation transcript:
RMAUG Professional Development Series 2/11/09 Dwight Reifsnyder
2 “If you have an apple and I have an apple and we exchange apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.” George Bernard Shaw
Codec background and concepts Comparisons and basic features Voice Codec specifics Application in an Avaya environment
Codec is short for Coder/Decoder Just like a Dick Tracy! But what are the concepts involved?
Examples of coding include: ◦ Pictures ◦ Writing ◦ Music ◦ Language translation ◦ Encryption
1876 Alexander Graham Bell ◦ Audio to electricity 1894 Guglielmo Marconi ◦ Audio to radio 1916 Theodore Case ◦ Audio to optical
An analog or analogue signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e. analogous to another time varying signal. Analog is usually thought of in an electrical context; however, mechanical, pneumatic, hydraulic, and other systems may also convey analog signals
1937 - Alec H. Reeves ◦ Pulse Code Modulation invented (PCM) 1942 - John V. Atanasoff, Clifford Berry ◦ First computer 1962 – Bell Labs ◦ PCM first used in commercial telephony
A digital system uses discrete (discontinuous) values, usually but not always symbolized numerically (hence called "digital") to represent information. By contrast, non- digital (or analog) systems use a continuous range of values to represent information.
The word digital is most commonly used in computing and electronics, especially where real-world information is converted to binary numeric form as in digital audio and digital photography.
Analog ◦ Continuous, modulates in direct relation to original data Digital ◦ Discrete data (individual values) with no intuitive or obvious correlation to original data
Encoding is changing form. Data may be encoded, transmitted, stored, and decoded Analog (encoding or transmission) Digital (encoding or transmission)
TIF (TIFF) Tagged Image File Format PNG Portable Network Graphic GIF Graphics Interchange Format JPG (JPEG) Joint Photographic Experts Group
There are many codec choices – the goal is for it to be transparent to the user Codecs can contain multiple encoding/compression steps Codec choice should consider type of audio, available bandwidth, and CPU usage
There a many audio codecs ◦ Quicktime ◦ Real Player ◦ MP3 Voice Specific Codecs ◦ Industry Standard (ITU) ◦ Optimized for speech
ITU-T Codec Standard Coding Scheme Used Bit RateEncoding Delay Time Mean Opinion Score G.711PCM64 kbps<1 msec4.7 G.722SB-ADPCM64 kbps4 msec4.5 G.726ADPCM32 kbps1 msec4.2 G.728LC-CELP16 kbps2 msec4.2 G.729CS-ACELP8 kbps15 msec4.2 G.723.1MPMLQ6.3 kbps37.5 msec3.98 G.723.1ACELP5.3 kbps37.5 msec3.5
For most users, the main consideration in choosing a codec is bandwidth This can be complex when considering calls between multiple regions