spa_io_clock Struct Reference

Absolute time reporting. More...

#include <spa/node/io.h>

Data Fields
uint32_t	flags
	Clock flags.
uint32_t	id
	Unique clock id, set by host application.
uint64_t	nsec
	Time in nanoseconds against monotonic clock (CLOCK_MONOTONIC).
struct spa_fraction	rate
	Rate for position/duration/delay/xrun.
uint64_t	position
	Current position, in samples @ rate.
uint64_t	duration
	Duration of current cycle, in samples @ rate.
int64_t	delay
	Delay between position and hardware, in samples @ rate.
double	rate_diff
	Rate difference between clock and monotonic time, as a ratio of clock speeds.
uint64_t	next_nsec
	Estimated next wakeup time in nanoseconds.
struct spa_fraction	target_rate
	Target rate of next cycle.
uint64_t	target_duration
	Target duration of next cycle.
uint32_t	target_seq
	Seq counter.
uint32_t	cycle
	incremented each time the graph is started
uint64_t	xrun
	Estimated accumulated xrun duration.

Detailed Description

Absolute time reporting.

Nodes that can report clocking information will receive this io block. The application sets the id. This is usually set as part of the position information but can also be set separately.

The clock counts the elapsed time according to the clock provider since the provider was last started.

Driver nodes are supposed to update the contents of SPA_IO_Clock before signaling the start of a graph cycle. These updated clock values become visible to other nodes in SPA_IO_Position. Non-driver nodes do not need to update the contents of their SPA_IO_Clock.

The host generally gives each node a separate spa_io_clock in SPA_IO_Clock, so that updates made by the driver are not visible in the contents of SPA_IO_Clock of other nodes. Instead, SPA_IO_Position is used to look up the current graph time.

A node is a driver when spa_io_clock::id in SPA_IO_Clock and spa_io_position.clock.id in SPA_IO_Position are the same.

Field Documentation

flags

uint32_t spa_io_clock::flags

Clock flags.

id

uint32_t spa_io_clock::id

Unique clock id, set by host application.

Examples

midi-src.c.

nsec

uint64_t spa_io_clock::nsec

Time in nanoseconds against monotonic clock (CLOCK_MONOTONIC).

This fields reflects a real time instant in the past. The value may have jitter.

rate

struct spa_fraction spa_io_clock::rate

Rate for position/duration/delay/xrun.

Examples

midi-src.c.

position

uint64_t spa_io_clock::position

Current position, in samples @ rate.

Examples

midi-src.c.

duration

uint64_t spa_io_clock::duration

Duration of current cycle, in samples @ rate.

Examples

audio-dsp-filter.c, audio-dsp-src.c, and midi-src.c.

delay

int64_t spa_io_clock::delay

Delay between position and hardware, in samples @ rate.

rate_diff

double spa_io_clock::rate_diff

Rate difference between clock and monotonic time, as a ratio of clock speeds.

next_nsec

uint64_t spa_io_clock::next_nsec

Estimated next wakeup time in nanoseconds.

This time is a logical start time of the next cycle, and is not necessarily in the future.

target_rate

struct spa_fraction spa_io_clock::target_rate

Target rate of next cycle.

target_duration

uint64_t spa_io_clock::target_duration

Target duration of next cycle.

target_seq

uint32_t spa_io_clock::target_seq

Seq counter.

must be equal at start and end of read and lower bit must be 0

cycle

uint32_t spa_io_clock::cycle

incremented each time the graph is started

xrun

uint64_t spa_io_clock::xrun

Estimated accumulated xrun duration.

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The documentation for this struct was generated from the following file:

• spa/node/io.h