ADPCM
Adaptive Differential Pulse Code Modulation
Encodes the differences between samples
- The change between 8-bit value of the last time interval and the current one
- Requires only 4 bits since the change is small
? Only 4 bits/sample (instead of 8 bits/sample),
- Requires 4 x 8000 = 32 Kbps (half of PCM)
- Makes it possible to for IM to send voice signals as digital signals using modems (which has ឨ Kbps)
Can also use lower sampling rates, at 8, 16 kbps
- Lower quality voice signals.