Real time device driver interface apparatus and method therefor

Abstract

A method and apparatus for interfacing a device driver in real time applications are provided. On input, the device driver is probed to determine a data sample block size supported by the device driver. The device driver delivers data samples to a buffer at each interrupt. The buffer is accessed to determine the presence of data in at least one buffer entry, or block. At each such access, a first counter is incremented to point to a next buffer entry to be accessed. One or more buffer entries are filled at each interrupt, with any data samples not sufficient to fill an entry held by the device driver until a subsequent interrupt. A second counter is incremented by the number of entries filled by the device driver. The size of each block in the buffer is incremented until the number of data samples held by the device driver between each interrupt corresponds to the size of the block, wherein each of the first and second counters increment by one, on each access to the buffer. On output, a display cursor is synchronized with an audio signal being played by storing, in a buffer, a frame number associated with each block of data samples sent to the device driver. A head pointer tracks each entry in the buffer as the frame number is stored. As each corresponding frame is played a tail pointer is incremented to point to the buffer entry containing the frame number of a next set of data samples to be played. If the position of the display cursor corresponds to a frame earlier than the position of the last frame output by the device driver, the position of the cursor is repeatedly updated until the cursor position coincides with the position of the last frame output by the device driver.