Audio round-trip latency has multiple additive sources and can be quantified with a loopback pulse test

Round-trip audio latency accumulates across several stages: analog-to-digital conversion, audio buffer size (block samples / sample rate), driver and OS scheduling overhead, DSP computation, and digital-to-analog conversion. On general-purpose computers, OS scheduling adds unpredictable jitter; Bela’s interrupt-driven kernel eliminates scheduler jitter, leaving mainly conversion and buffer delay. Latency is measured by sending a pulse to the audio output, looping it back to the input, and timing the round trip — this gives the actual end-to-end delay affecting performer responsiveness. Latencies above roughly 10-20 ms degrade perceived instrument quality for trained performers. Understanding each source lets a builder reduce the dominant contributor rather than guessing.

Examples

The Bela latency tutorial builds an automatic tester that emits a regular pulse and measures how long it takes to return via a loopback cable. An oscilloscope and patch cable can perform the same measurement externally.

Assessment

Identify three distinct latency sources in a laptop software synthesizer. Explain which are reduced on Bela and which architectural feature achieves each reduction.