Multimedia driver support in the FreeBSD operating system

In this paper we will discuss the motivation, design, implementation issues, and applications for the audio and the video acquisition drivers which are available in FreeBSD [1]. Both systems have been designed from scratch, with special attention paid to the effective transfer and synchronization of data between the hardware and advanced applications. The main focus in the design of the audio driver was for supporting multimedia applications, which often require full duplex operation and have strict synchronization requirements. This suggested the definition of a new software interface, simpler to use than the previously existing OSS (Voxware) driver. The driver is backward compatible with the OSS API due to the large base of applications that use this API. The video acquisition driver focuses on providing flexible access to the acquisition device and the ability to suit the needs of different applications, from simple TV viewers to video conferencing programs. The driver provides memory mapped access to the capture buffer, flexible support for synchronization with the application, and supports the various capture formats and scaling capabilities that are available from the video acquisition hardware.