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Implementation and Quantitative Analysis of a Real-time Sound Architecture

出版	Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009
URL	http://books.google.com.hk/books?id=PjxInQAACAAJ&hl=&source=gbs_api

註釋Several available free software audio solutions were analyzed, and Jackdmp--a C++ reimplementation of the renowned JACK Audio Connection Kit--was selected as the most appropriate solution for a real-time audio architecture on DROPS. The JACK sound architecture provides the lowest processing latency possible on a desktop computer for a given set of sound card parameters. It reduces the latency jitter caused by software to zero and synchronizes streams at sample accuracy. A real-time admission scheme for JACK clients is proposed. The execution time of different typical JACK clients was analyzed with measurements to validate the assumptions the proposal is based on, but also to gain further knowledge about their timing behavior. The measurements showed that the condition set by Paul Davis--the time to process a client must be a linear function of the buffer size--holds for all tested clients. Jackdmp was ported to DROPS. The developed design of the port and its implementation is documented here. Measurements showed that--although the real-time performance of the Linux kernel is continuously being improved in the mainline and on special external branches--DROPS can provide a signaling latency that is two times lower on average than the values that can be achieved on the same machine running with a low latency patched Linux kernel. Thus, it can be stated that DROPS is well-suited for real-time audio processing and that the pursued path to use it as the foundation of a truly real-time capable audio workstation should be followed.