While working with virtual instruments and live input monitored tracks, it is important for audio to be streamed at low latency in order to minimize delay.
Although SONAR supports streaming audio at very low latency, there are cases where internal buffering can cause additional latency. The most common scenario is when using plug-ins that require Automatic Plug-in Delay Compensation (PDC). PDC is the process of delay compensating other normal tracks so they are synchronized with the delayed audio produced by the plug-ins.
Whenever delay compensation takes place on a track that has a live input (an input monitored track or synth track), it is delayed by the required amount to synchronize it with other tracks. In some cases, the delay can be noticeable and make live tracking difficult.
The Live Input PDC Override toggle lets you disable delay compensation on live tracks, thereby removing the latency during playback and recording of such tracks. Since it's a toggle, you can quickly turn it on to complete your tracking at low latency, and turn it off when finished to hear the track compensated as normal.
Regardless of whether Live Input PDC Override is enabled or disabled, recorded audio is placed on the timeline at the correct position as recorded.
Live Input PDC Override is ignored during a bounce/export or freeze operations.
Tip: You can control which tracks are delay overridden by enabling input monitoring only for those tracks. For more information, see Input monitoring.
Цитата из хелпа в Sonar X1 PE