PsychVideoCapture -- Video capture support
Psychtoolbox has built-in
Screen-Subfunctions that allow you
to control and use standard video capture equipment to capture
live video from a camera or other supported video source in
real-time with low latency.
This is useful for studies on (manipulated) visual feedback,
e.g., action-perception studies, as well as for future
applications like vision based eye-trackers.
The M-Files in this folder use the
Screen - Low-level functions
to provide more convenient high-level access to standard video
capture tasks, e.g., setup of the camera or a video feedback
loop with low and controlled latency.
THIS IS EXPERIMENTAL CODE FOR NOW! It is well tested and known
to work perfectly on Linux, but support on
MacOS-X and Windows
is not yet as feature rich, flexible and mature as on Linux.
Especially, the OS-X and Windows versions are not as extensively
tested. Some of the functions here are work in progress, useful,
but not finished.
OS-X & Windows: We use the Sequence-Grabber API of Apples Quicktime
for video capture on OS-X and Windows. On Windows, you'll need
to install a Quicktime compatible video digitizer component, e.g.,
WinVDIG, which can be freely downloaded from
http://www.vdig.com/WinVDIG/
On
MacOS-X 10.4, video digitizers are already installed.
Windows and
MacOS-X support USB-Webcams, Firewire digital cameras
conforming to the IIDC 1.0 machine vision camera specification,
standard framegrabber cards and standard digital video cameras.
-> Everything that is supported by the operating system.
On Linux, currently only Firewire digital cameras are supported that
conform to the IIDC 1.0 machine vision camera specification.
Internally we use the excellent and free
LibDC1394 library. See
http://damien.douxchamps.net/ieee1394/libdc1394/index.php
for information, forums and links to the IIDC-Spec.
A list of supported cameras can be found here:
http://damien.douxchamps.net/ieee1394/cameras/index.php
The Linux version is the most mature and well-tested one. It allows
very convenient and fine-grained control over many aspects and
settings of the cameras, it reliably can drive multiple cameras
in parallel (tested with two cameras) and it has excellent timing,
very low capture latency and highly accurate built-in timestamping
code. The reported timestamps are accurate to a few dozen microseconds.
You will need Linux kernel 2.4.21 or later or Linux 2.6.16
or later for best performance, but these are part of any recent
distribution.
All IIDC compliant cameras should work. For the Basler A602f greyscale
high performance camera and the cheap and good Unibrain Fire-i camera,
the
PsychCamSettings - Tool provides especially convenient access to
the camera settings.
All cameras supported by the operating system are supported, but there
is only very limited support for changing camera settings and accessing
special features. Capture works reliably, but the capture latency is
pretty much unknown and the timing mechanisms for retrieving capture
timestamps are hidden in Apples Quicktime implementation and therefore
their reliability and internal working is unknown.
PsychCamSettings - Function for programmatically querying and setting
camera parameters like exposure time, gain, brightness
color saturation and such. Can also estimate the
internal latency of the camera for known models,
currently Basler A602f and Unibrain Fire.i
PsychGetCamIdForSpec - Return deviceIndex of a specified camera.
PsychOpenEyes - Control interface for PTB's integrated vision based
eyetracker, based on the
OpenEyes toolkit.
- Interactive tool for setting up a camera and writing
the final settings into a .mat file for later use
by experiment scripts.
PsychVideoDelayLoop - Full, feature rich implementation of a live
video feedback loop with controllable latency.
See its help for a list of features.
Psychtoolbox/Contents.m
The following 8 page(s) belong to PsychVideoCapture