Supported by ...


All Pixelink cameras.


Description


The frame interval and the required bandwidth on the communication bus are fixed by the Frame Rate value. The available frame rate range depends on the bus technology, the current exposure time, pixel format, ROI and/or pixel addressing.  Programmers are recommended to check the minimum and maximum value after one of these parameters has been changed.


When continuous auto frame rate is off, the frame rate can be set to any value within the permitted range. The camera will use this value as a ‘target’ frame rate. However, if for instance the current exposure is sufficiently long that is not possible to achieve the target frame rate, then the camera will use a lesser frame rate (until such time as the exposure is lowered). Querying FEATURE_ACTUAL_FRAME_RATE will return the frame rate that the camera will use for streaming image data.


After a change to ROI, pixel format or pixel addressing mode, the camera will attempt to maintain the same frame rate; Or, when this is not possible, the closest possible frame rate. 


When continuous auto frame rate is on, the camera selects what it believes to be a "good" frame rate, taking into account factors like exposure time and the interface. In this mode we attempt to avoid dropped/lost frames, and so the camera will choose a frame rate that reduces the likelihood of that happening. 


Please note: For some older FireWire cameras, the exposure time (Shutter) is limited by the frame rate value dynamically. For these cameras, when continuous auto frame rate is off and the Frame Rate value is changed, the minimum and maximum limits on the Shutter control will change accordingly.  The Shutter value will be forced to lie within these limits.  



API Control

PxLGetFeaturePxLSetFeature


Feature ID
Number of Params
Parameters
Units
Restrictions
FEATURE_FRAME_RATE
Frame rate of the video stream
1
fValue
Frames/second
N/A


Note: To turn the frame rate control OFF, set the FEATURE_FLAGS to FEATURE_FLAG_OFF. Turning frame rate control off, has the same effect as enabling continuous auto adjustment; whereby the camera will choose the frame rate – maximizing its value while avoiding dropped/lost frames.


Note: The stream state must be off (STREAM_OFF) to modify this feature. See PxLSetStreamState.


 

 Feature Flags


Camera
Presence
Read Only
Auto
Manual
One-time Auto
Off
CiD
All Cameras
Yes
No
No
Yes
No
Yes
Yes


Parameters
 
 

Camera
Parameter
Unit
Type
Min
Max
Default
Step Size
Comments
All
Frame Rate
fps
Absolute
2
Varies
Max ISO
Varies
Step Size varies with the number of rows in the image.  It is essentially the readout time of one row.  The max frame rate is a function of the shutter speed, ROI, pixel format, trigger settings, interface bandwidth, the capabilities of the driver and the quality of the cables used.