| A through H |
Definition of Terms 
|
| ADPCM |
Adaptive Differential Pulse Code Modulation. ADPCM is a speech coding method that achieves bit rate reduction through
the use of adaptive prediction and adaptive quantization. It is a reduced bit rate variant of PCM audio encoding.
ADPCM increases the number of subchannels carried by a T-1 or DS-1 circuit and reduces the capacity in each subchannel
to 4.8 Kbps. This allows analog voice signals to be carried on a 32 Kbps digital channel. Sampling is performed
at 8 KHz with 3 or 4 bits used to describe the difference between adjacent samples. |
| A-Law |
The PCM voice coding and companding standard for European telephone networks. The analog signal is compressed from
a 13-bit word and encoded into an 8-bit scheme composed of 7 bits for magnitude and 1 sign bit. The data rate for
and individual voice channel when encoded using A-law technique is 8,000 samples per second X 8 bits per sample
= 64,000 bits per second. |
| Companding |
Process of compressing a signal prior to transmission and expanding the signal at the receiver. |
| G recommendations |
A series of standards defined by the International Telecommunications Union (ITU) covering transmission facilities. |
|
G.723
|
An ITU-T Recommendation; Dual Rate Speech Coder for media communications transmitting at 5.3 and 6.3 Kbps. This
Recommendation specifies a coded representation that can be used for compressing the speech or other audio signal
component of multi-media services at a very low bit rate as part of the overall H.324 family of standards. |
| G.726 |
An ITU-T Recommendation; Coding of analogue signals by methods other than PCM using using 40, 32, 24, 16 Kbit/s
adaptive differential pulse code modulation (ADPCM). Recommendation G.726 sets out the characteristics recommended
for the conversion of a 64 kbit/s A-law or µ-law pulse code modulation (PCM) channel to and from a 40, 32,
24 or 16 kbit/s channel. The conversion is applied to the PCM bit stream using an ADPCM transcoding technique.
Recommendation G.726 provides an outline description of the ADPCM transcoding algorithm including ADPCM encoding
and decoding algorithms respectively. |
| G.726a |
Annex A to Recommendation G.726 (11/94) - Extensions of Recommendation G.726 for use with uniform-quantized input
and output. Xilinx 32-Channel ADPCM core is not G.726a compliant. |
| H.324 |
Standard for analog POTS telephone line based videoconferencing via modems. H324 contains several standards for
videoconferencing including G.723 for real-time audio compression/decompression. |
| I through Z |
|
| mu Law |
The PCM voice coding and companding standard for North American and Japanese telephone networks. Generally know
as µ-law, the analog signal is compressed from a 14-b word and encoded into an 8-bit scheme composed of 7
bits for magnitude and 1 sign bit. The data rate for and individual voice channel when encoded using µ-law
technique is 8,000 samples per second X 8 bits per sample = 64,000 bits per second. |
| PCM |
Pulse Code Modulation. A form of modulation in which information signals are sampled at regular intervals, and
a series of pulses, coded to represent the amplitude of the information signal at the time of the sampling, are
transmitted. PCM is the most common method to encode an analog voice signal into digital bit stream. |
