.file extension AD3 - ADPCM 3-bit compressed voice file
File extension AD3 description:
AD3 file suffix is associated with ADPCM. 3-bit compressed voice file.
Adaptive Differential Pulse Code Modulation (ADPCM) codecs are waveform codecs which instead of quantizing the speech signal directly, like PCM codecs, quantize the difference between the speech signal and a prediction that has been made of the speech signal. If the prediction is accurate then the difference between the real and predicted speech samples will have a lower variance than the real speech samples, and will be accurately quantized with fewer bits than would be needed to quantize the original speech samples. At the decoder the quantized difference signal is added to the predicted signal to give the reconstructed speech signal. The performance of the codec is aided by using adaptive prediction and quantization, so that the predictor and difference quantizer adapt to the changing characteristices of the speech being coded.