ALSA project - the C library reference

Timer interface

Timer interface is designed to use internal timers in sound hardware, but it can be driven with any timer.

# General overview

The timer implementation uses ring buffer to store information about timing events. In this buffer is recorded count of ticks and current tick resolution in nanoseconds.

# Opening

Timer devices can be opened in two ways. When SND_TIMER_OPEN_NONBLOCK flag is used, then the open functions return immediately with -EBUSY error code when resources are occupied with another application. When SND_TIMER_OPEN_NONBLOCK is not used (by default) the open functions block the application requesting device until resources are not free.

# Events

Events are read via snd_timer_read() function.

# Examples

The full featured examples with cross-links:

Simple timer test program
  example code

  This example shows opening a timer device and reading of timer events.