5.4.1 Control Logic

26.4483GPPCodec for Enhanced Voice Services (EVS)Jitter Buffer ManagementRelease 17TS

Figure 3: Control Logic of the EVS Jitter Buffer Management Solution

The Control Logic module compares the playout delay with the target playout delay as outlined in Figure 3. If the difference exceeds a threshold, it triggers adaptation to modify the playout delay and therefore also the depth of the De-Jitter Buffer. Different types of adaptation are supported and selected in a signal-adaptive manner. During comfort noise (SID-flag is active), frame-based adaptation will be triggered and executed by the De-Jitter Buffer module. During active periods, signal-based adaptation is triggered and executed by the Time Scale Modification module.

An initialization phase is used at startup. The JBM solution outputs audio samples before receiving and decoding the first frame which is received with some network delay. During this initialization phase the audio decoder is not used yet and PCM buffers are returned filled with zero samples.