Latency refers to a short period of delay (usually measured in milliseconds) required for the conversion between analog and digital representations of the sound data. Devices such as computers can only process digital data. Thus, the analog data it receives on microphone or line-in inputs must be converted to digital data. After processing of data, the processed data must be converted back to an analog signal before it can be output to speakers and played back.
This conversion between analog and digital takes a short amount of time, which is known as latency. Although this process consumes a very small interval, it can have a cumulative effect if the data is handed off by several layers of software.
One example of latency is a musical keyboard connected to a computer. When the user hits a key, an audio signal, which is analog, is transferred along the connecting wire in the form of electrical current. The computer would then convert the signal to a digital format and process it according to any settings input by the user. After the processing is complete, the processed digital signal is converted to an analog sound wave (represented by current in the wire), which is then sent to the speaker.
Latency in Computer Audio
Latency can be a particular problem in current Microsoft Windows audio platforms, but is much less so in Apple's Mac OS X and most Linux operating systems[dubious â€“ discuss]. A popular workaround is Steinberg's ASIO, which bypasses these layers and connects audio signals directly to the sound card's hardware. Most professional and semi-professional audio applications utilize the ASIO driver, allowing Windows users to work with audio in real time, i.e. digital multitrack recording.
Latency in Broadcast
Audio latency can also be experienced in broadcast systems where someone is contributing to a live broadcast over a satellite or similar link with high delay, where the person in the main studio has to wait for the contributor at the other end of the link to react to questions. Latency in this context could be between several hundred milliseconds and a few seconds. Dealing with audio latencies as high as this takes special training in order to make the resulting combined audio output reasonably acceptable to the listeners. Wherever practical, it is important to try to keep live production audio latency low throughout the production system in order to keep the reactions and interchange of participants as natural as possible. A latency of 10 milliseconds or better is the target for audio circuits within professional production structures, local circuits should ideally have a latency of 1 millisecond or better.