PsychPortAudio(‘GetStatus’)

Psychtoolbox>PsychPortAudio.{mex*} subfunction

Returns ‘status’, a struct with status information about the current state of
device ‘pahandle’.
The struct contains the following fields:
Active: Can be 1 if playback or recording is active, or 0 if playback/recording
is stopped or not yet started.
RequestedStartTime: Is the requested start time of the audio stream after start
of playback/recording. StartTime: Is the real start time of the audio stream
after start of playback/recording. If both, playback and recording are active
(full-duplex mode), it is the start time of sound playback, ie an estimate of
when the first sample hit the speakers. Same goes for pure playback.
CaptureStartTime: Start time of audio capture (if any is active) - an estimate
of when the first sound sample was captured. In pure capture mode, this is
nearly identical to StartTime, but whenever playback is active, StartTime and
CaptureStartTime will differ. CaptureStartTime doesn’t take the user provided
‘LatencyBias’ into account.
RequestedStopTime: The requested stop / sound offset time for playback of
sounds, as selected via the ‘stopTime’ paramter in the ‘Start’,
‘RescheduleStart’ or ‘Stop’ function. This will show a very large (~ infinite)
value if no stop time has been sprecified.
EstimatedStopTime: Estimated time when sound playback has stopped. This is an
estimate of when exactly the last audio sample will leave the speaker. The value
is zero as long as the estimate isn’t available. Due to the latency involved in
sound playback, the value may become available a few msecs before or after
actual sound offset.
CurrentStreamTime: Estimate of when the most recently submitted sample will hit
the speaker. This corresponds roughly to ‘PositionSecs’ below, but in absolute
realtime.
ElapsedOutSamples: Total number of samples played out since start of playback.
This count increments monotonically from start of playback to stop of playback.
This denotes the absolute sample position that will hit the speaker at time
‘CurrentStreamTime’.
PositionSecs is an estimate of the current stream playback position in seconds
within the current playback loop of the current buffer. it’s not totally
accurate, because it measures how much sound has been submitted to the sound
system, not how much sound has left the speakers, i.e., it doesn’t take driver
and hardware latency into account.
SchedulePosition: Current position in a running schedule, if any.
XRuns: Number of dropouts due to buffer overrun or underrun conditions. This is
not perfectly reliable, as the algorithm can miss some dropouts. Iow.: A
non-zero or increasing value means that audio glitches during playback or
capture happened, but a zero or constant value doesn’t mean everything was
glitch-free, because some glitches can’t get reliably detected on some operating
systems or audio hardware.
TotalCalls, TimeFailed and BufferSize are only for debugging of PsychPortAudio
itself.
CPULoad: How much load does the playback engine impose on the CPU? Values can
range from 0.0 = 0% to 1.0 for 100%. Values close to 1.0 indicate that your
system can’t handle the load and timing glitches or sound glitches are likely.
In such a case, try to reduce the load on your system.
PredictedLatency: Is the latency in seconds of your driver+hardware combo. It
tells you, how far ahead of time a sound device must be started ahead of the
requested onset time via PsychPortAudio(‘Start’…) to make sure it actually
starts playing in time. High quality systems like Linux or MacOS/X may allow
values as low as 5 msecs or less on standard hardware. Other operating systems
may require dozens or hundreds of milliseconds of headstart. Caution: In
full-duplex mode, this value only refers to the latency on the sound output, not
in the sound input! Also, this is just an estimate, not 100% reliable.
LatencyBias: Is an additional bias setting you can impose via
PsychPortAudio(‘LatencyBias’, pahandle, bias); in case our drivers estimate is a
bit off. Allows fine-tuning.
SampleRate: Is the sampling rate for playback/recording in samples per second
(Hz).
OutDeviceIndex: Is the deviceindex of the playback device, or -1 if not opened
for playback. You can pass OutDeviceIndex to PsychPortAudio(‘GetDevices’, [],
OutDeviceIndex)); to query information about the device.
InDeviceIndex: Is the deviceindex of the capture device, or -1 if not opened for
capture.
RecordedSecs: Is the total amount of recorded sound data (in seconds) since
start of capture.
ReadSecs: Is the total amount of sound data (in seconds) that has been fetched
from the internal buffer. The difference between RecordedSecs and ReadSecs is
the amount of recorded sound data pending for retrieval.

###See also: Open GetDeviceSettings