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Re: UVC camera control.
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Re: UVC camera control.

The sequence grabber APIs do not allow you access to the UVC controls.

The QTKit APIs do not expose those controls, although the underlying components do have acces to them. You need to file a bug at asking for access to camera controls from QTKit.

In the meantime, you "could" use IOUSBLib to access those, but this is somewhat complicated and you need to have a good understanding of the UVC spec. These controls are all control requests to the IOUSBDevice, so in theory, you can do it.

Your best bet is to get QTKit to expose those APIs. I have requested that, but if more developers ask for it, it might raise the priority.

- Fernando

On Sep 24, 2008, at 10:02 AM, arri wrote:


i'm grabbing frames from a Terratec Terracam X2 webcam. it complies
with the UVC standard, so just works.
however, i'd like to be able to manually control certain features such
as whitebalance, exposure etc. but currently there's no standard
interface to those features in osx, either through sequence grabber or

according to one of the Terratec-developers, on Windows you can
control these camera-features through the MS VideoProcAmp API.

i'm not exactly a usb-device-driver expert, but i'm wondering what the
options are for creating my own interface.
where should i look if i wanted to talk to the camera to control such
features? would it be a feasible task for someone without any
experience in the field? (i'm not afraid and don't mind a little
and is it even possible to do that, while also capturing video from
the device using apples' drivers?
or is it all a little more complicated than i'm hoping/thinking?

posts on Quicktime-API list seem to suggest it's not possible, but
they only look at handling things through VDIG/seqeunce grabber, and
not at talking to the device directly using IOKit.


------ output of USB Prober:

High Speed device @ 2 (0xFD300000):
.............................................   Miscellaneous/Common
Class device: "TerraTec TerraCam X2\000"
   Device Descriptor
   Configuration Descriptor
       Length (and contents):   783
       Number of Interfaces:   5
       Configuration Value:   1
       Attributes:   0x80 (bus-powered)
       MaxPower:   500 ma
       Interface Association   Video/Interface Collection
       Interface #0 - Video/Control
           Alternate Setting   0
           Number of Endpoints   1
           Interface Class:   14   (Video)
           Interface Subclass;   1   (Control)
           Interface Protocol:   0
           VDC (Control) Header
           VDC (Control) Input Terminal
               Length (and contents):   18
               bDescriptorType:   0x24
               bDescriptorSubType:   0x2
               Terminal ID   1
               Input Terminal Type:   0x201 (Camera Sensor)
               Input Terminal ID:   0 [NONE]
               Input Terminal String Index:   0 [NONE]
               Minimum Focal Length   0
               Maximum Focal Length   0
               Ocular Focal Length   0
               Controls Supported   Description
                      Auto Exposure Mode
                      Exposure Time (Relative)
           VDC (Control) Processing Unit
               Length (and contents):   12
               bDescriptorType:   0x24
               bDescriptorSubType:   0x5
               Unit ID:   3
               Source ID:   1
               Digital Multiplier (100X):   0
               Controls Supported   Description
                      White Balance Temperature
                      Power Line Frequency
                      White Balance Temperature, Auto
               Processing Unit String Index:   0 [NONE]
           VDC (Control) Extension Unit
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 >UVC camera control. (From: arri <email@hidden>)

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