Continuously Variable Slope Delta modulation is a voice coding method. It is a delta modulation with variable step size (adaptive delta modulation), first proposed by Greefkes and Riemens in 1970
AC3 is an audio file format that uses Audio Codec 3. Dolby Digital developed AC3 that gives a surround sound experience. It is mostly used in DVD or Blue-Ray disks. It supports 6 Channels music and can provide 6 different sound effects. This lossy format effectively encodes the surround sound system.