1.1 Existing Distributed Synchronization Techniques Digital audio is one example of a distributed multimedia application. A sender digitizes analog audio inputs by sampling at a regular rate and applying quantization to the sampled values. Additionally, it may compress or encode the data so that it can send less than a full sample. This audio data is then packetized and transmitted over the network. The receiver decodes the network packets, assembles them in the correct order, and recreates the sound for the user.
Synchronization is accomplished in digital audio applications through sequence numbers and buffers.
Sequence numbers allow receivers to detect losses and correctly reassemble the sequence of audio samples. Receivers also buffer data as it arrives, thus delaying presentation to the user by a small amount of time. Applications attempt to delay presentation enough to allow delayed packets to arrive before they must be presented to the user. The amount of delay applied to the audio packets is altered to compensate for perceived changes in network performance. The basic feature of audio which is used for synchronization is the talk spurt .