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The Adaptive Multi-Rate (AMR, AMR-NB or GSM-AMR) audio codec is an audio compression format optimized for speech coding. AMR is a multi-rate narrowband speech codec that encodes narrowband (200–3400 Hz) signals at variable bit rates ranging from 4.75 to 12.2 kbit/s with toll quality [ 3 ] speech starting at 7.4 kbit/s.
The frequencies from 6.4 kHz to 7 kHz are only transmitted in the highest bitrate mode (23.85 kbit/s), while in the rest of the modes the decoder generates sounds by using the lower frequency data (75–6400 Hz) along with random noise (in order to simulate the high frequency band).
Extended Adaptive Multi-Rate – Wideband (AMR-WB+) is an audio codec that extends AMR-WB. It adds support for stereo signals and higher sampling rates. Another main improvement is the use of transform coding (transform coded excitation – TCX) additionally to ACELP. This greatly improves the generic audio coding.
CW Skimmer is a multi-channel Morse code decoder and analyzer program for Microsoft Windows.It was created by Alex Shovkoplyas, VE3NEA, and is marketed by Afreet Software, Inc.
Chart of the Morse code 26 letters and 10 numerals [1]. This Morse key was originally used by Gotthard railway, later by a shortwave radio amateur [2]. Morse code is a telecommunications method which encodes text characters as standardized sequences of two different signal durations, called dots and dashes, or dits and dahs.
Morse code is called the original digital mode. Radio telegraphy, designed for machine-to-machine communication is the direct on / off keying of a continuous wave carrier by Morse code symbols, often called amplitude-shift keying or ASK, may be considered to be an amplitude modulated mode of communications, and is rightfully considered the first digital data mode.
Hardware audio codecs send and receive digital data using buses such as AC'97, SoundWire, [5] I²S, SPI, I²C, etc. Most commonly the digital data is linear PCM , and this is the only format that most codecs support, but some legacy codecs support other formats such as G.711 for telephony.
It is a delta modulation with variable step size (i.e., special case of adaptive delta modulation), first proposed by Greefkes and Riemens in 1970. CVSD encodes at 1 bit per sample, so that audio sampled at 16 kHz is encoded at 16 kbit/s. The encoder maintains a reference sample and a step size. Each input sample is compared to the reference ...