Abstract
Streaming media applications provide an interesting mix of requirements that include not necessarily hard real time support, but rather, guarantees for the resources used by such applications. This paper describes our experience in enabling a Personal Video Recorder (PVR) application (performing record and playback of live and pre-recorded streams) on a Linux based embedded platform. We found that while the standard Linux kernel may not be applicable

for hard real time applications it is quiet well suited as a platform for implementing media streaming applications. While we observed that the operations like playback of video streams is perfect, the functions such as simultaneous record and playback of multiple video streams, time-shift operations etc., do require specialized support that is not directly provided by the Linux kernel. In this paper we describe areas that we identified, in the Linux kernel and the application, and approaches to tackle the same to improve performance of the application, with regard to the above operations. Primarily these include, (1) application buffering model and I/O mechanism (using direct I/O vs. buffered I/O) (2) the file system used for media streaming (3) soft real time enhancements to the kernel (4) reducing time taken for I/Os to the hard disk (5) using fast data transfer modes for disk devices.

Author Thiruvengada Govindan

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