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. 


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


PxLGetFeature, PxLSetFeature


Feature ID

Number of Params

Parameters

Units

Restrictions


FEATURE_FRAME_RATE

Frame rate of the video stream

1

fValue

Frames/second

N/A


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.