pa_timing_info Struct Reference

A structure for all kinds of timing information of a stream. More...

Data Fields
struct timeval	timestamp
	The time when this timing info structure was current.
int	synchronized_clocks
	Non-zero if the local and the remote machine have synchronized clocks.
pa_usec_t	sink_usec
	Time in usecs a sample takes to be played on the sink.
pa_usec_t	source_usec
	Time in usecs a sample takes from being recorded to being delivered to the application.
pa_usec_t	transport_usec
	Estimated time in usecs a sample takes to be transferred to/from the daemon.
int	playing
	Non-zero when the stream is currently not underrun and data is being passed on to the device.
int	write_index_corrupt
	Non-zero if write_index is not up-to-date because a local write command that corrupted it has been issued in the time since this latency info was current .
int64_t	write_index
	Current write index into the playback buffer in bytes.
int	read_index_corrupt
	Non-zero if read_index is not up-to-date because a local pause or flush request that corrupted it has been issued in the time since this latency info was current.
int64_t	read_index
	Current read index into the playback buffer in bytes.
pa_usec_t	configured_sink_usec
	The configured latency for the sink.
pa_usec_t	configured_source_usec
	The configured latency for the source.
int64_t	since_underrun
	Bytes that were handed to the sink since the last underrun happened, or since playback started again after the last underrun.

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Detailed Description

A structure for all kinds of timing information of a stream.

See pa_stream_update_timing_info() and pa_stream_get_timing_info(). The total output latency a sample that is written with pa_stream_write() takes to be played may be estimated by sink_usec+buffer_usec+transport_usec. (where buffer_usec is defined as pa_bytes_to_usec(write_index-read_index)) The output buffer which buffer_usec relates to may be manipulated freely (with pa_stream_write()'s seek argument, pa_stream_flush() and friends), the buffers sink_usec and source_usec relate to are first-in first-out (FIFO) buffers which cannot be flushed or manipulated in any way. The total input latency a sample that is recorded takes to be delivered to the application is: source_usec+buffer_usec+transport_usec-sink_usec. (Take care of sign issues!) When connected to a monitor source sink_usec contains the latency of the owning sink. The two latency estimations described here are implemented in pa_stream_get_latency(). Please note that this structure can be extended as part of evolutionary API updates at any time in any new release.

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Field Documentation

pa_usec_t pa_timing_info::configured_sink_usec

The configured latency for the sink.

Since:

0.9.11

pa_usec_t pa_timing_info::configured_source_usec

The configured latency for the source.

Since:

0.9.11

int pa_timing_info::playing

Non-zero when the stream is currently not underrun and data is being passed on to the device.

Only for playback streams. This field does not say whether the data is actually already being played. To determine this check whether since_underrun (converted to usec) is larger than sink_usec.

int64_t pa_timing_info::read_index

Current read index into the playback buffer in bytes.

Think twice before using this for seeking purposes: it might be out of date a the time you want to use it. Consider using PA_SEEK_RELATIVE_ON_READ instead.

int pa_timing_info::read_index_corrupt

Non-zero if read_index is not up-to-date because a local pause or flush request that corrupted it has been issued in the time since this latency info was current.

int64_t pa_timing_info::since_underrun

Bytes that were handed to the sink since the last underrun happened, or since playback started again after the last underrun.

playing will tell you which case it is.

Since:

0.9.11

pa_usec_t pa_timing_info::sink_usec

Time in usecs a sample takes to be played on the sink.

For playback streams and record streams connected to a monitor source.

pa_usec_t pa_timing_info::source_usec

Time in usecs a sample takes from being recorded to being delivered to the application.

Only for record streams.

int pa_timing_info::synchronized_clocks

Non-zero if the local and the remote machine have synchronized clocks.

If synchronized clocks are detected transport_usec becomes much more reliable. However, the code that detects synchronized clocks is very limited and unreliable itself.

struct timeval pa_timing_info::timestamp

The time when this timing info structure was current.

pa_usec_t pa_timing_info::transport_usec

Estimated time in usecs a sample takes to be transferred to/from the daemon.

For both playback and record streams.

int64_t pa_timing_info::write_index

Current write index into the playback buffer in bytes.

Think twice before using this for seeking purposes: it might be out of date a the time you want to use it. Consider using PA_SEEK_RELATIVE instead.

int pa_timing_info::write_index_corrupt

Non-zero if write_index is not up-to-date because a local write command that corrupted it has been issued in the time since this latency info was current .

Only write commands with SEEK_RELATIVE_ON_READ and SEEK_RELATIVE_END can corrupt write_index.