1 research outputs found
Low Latency Audio Processing
PhDLatency in the live audio processing chain has become a concern for audio engineers and
system designers because significant delays can be perceived and may affect synchronisation
of signals, limit interactivity, degrade sound quality and cause acoustic feedback.
In recent years, latency problems have become more severe since audio processing has
become digitised, high-resolution ADCs and DACs are used, complex processing is
performed, and data communication networks are used for audio signal transmission in
conjunction with other traffic types. In many live audio applications, latency thresholds
are bounded by human perceptions. The applications such as music ensembles and live
monitoring require low delay and predictable latency. Current digital audio systems either
have difficulties to achieve or have to trade-off latency with other important audio
processing functionalities.
This thesis investigated the fundamental causes of the latency in a modern digital audio
processing system: group delay, buffering delay, and physical propagation delay and
their associated system components. By studying the time-critical path of a general
audio system, we focus on three main functional blocks that have the significant impact
on overall latency; the high-resolution digital filters in sigma-delta based ADC/DAC,
the operating system to process low latency audio streams, and the audio networking to
transmit audio with flexibility and convergence.
In this work, we formed new theory and methods to reduce latency and accurately predict
latency for group delay. We proposed new scheduling algorithms for the operating
system that is suitable for low latency audio processing. We designed a new system
architecture and new protocols to produce deterministic networking components that
can contribute the overall timing assurance and predictability of live audio processing.
The results are validated by simulations and experimental tests. Also, this bottom-up
approach is aligned with the methodology that could solve the timing problem of general
cyber-physical systems that require the integration of communication, software and
human interactions