There is a strong tendency towards using modern Personal Computers for various tasks they are not designed for. This also includes audio and video processing. Audio and Video data is real-time data. It needs to be dispatched within predefined and fixed time windows to avoid perceivable lags and dropouts. Neglecting this very fact, today's software solutions are built on General Purpose Operating Systems that do not guarantee any timing behaviour.

Target of this project is creating an open-source versatile real-time capable data aquisition, routing and manipulation framework. The “Audio” part in the name refers to the concepts' suitability for audio recording.

The goal of the software design is to maximize reliability. No sample must be lost during data aquisition or manipulation. Of course, one can't eliminate the possibility of too slow hardware, disk failure, network packet or connection loss and similar events. In these cases, the software must report an error immediately.

This paper describes a way to use a hard real-time operating system for the tricky task of reliably recording and reproducing audio samples and video frames. It relies on a working implementation. This implementation uses the Linux operating system, extended with real-time capabilities by RTLinux/Free. It is directed towards software developers with Linux knowledge. The concept described relies on Linux kernel mechanisms, real-time specific programming and hardware management.

Read full paper (PDF download)

 
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