Hello, On Tuesday, 30 October 2018 17:48:12 EET Kieran Bingham wrote: > On 30/10/2018 14:36, Jiri Slaby wrote: > > Hi, > > > > I have a Dell Lattitude 7280 with two webcams. The standard one works > > fine (/dev/video0). The other one is an IR camera (/dev/video1). The > > camera proper works fine and produces 340x374 frames. But there is an IR > > led supposed to light the object. The video is 30fps, but the LED seems > > to emit light only on half of the frames, i.e. on every second frame (15 > > fps). This makes the video blink a lot. The two consecutive frames look > > like: > > https://www.fi.muni.cz/~xslaby/sklad/mpv-shot0002.jpg > > https://www.fi.muni.cz/~xslaby/sklad/mpv-shot0003.jpg > > > > Do you have any ideas what to check/test? > > I have an HP Spectre with IR camera, and it also 'flashes' alternate frames. > > I assumed this was something to do with controlling the lighting for > face recognition some how. > > I'm fairly sure we don't control the 'IR flash' from the UVC. > > I wonder if there is a control parameter for the IR led in the > extension-units? [snip] > > VideoControl Interface Descriptor: > > bLength 18 > > bDescriptorType 36 > > bDescriptorSubtype 2 (INPUT_TERMINAL) > > bTerminalID 11 > > wTerminalType 0x0201 Camera Sensor > > bAssocTerminal 0 > > iTerminal 0 > > wObjectiveFocalLengthMin 0 > > wObjectiveFocalLengthMax 0 > > wOcularFocalLength 0 > > bControlSize 3 > > bmControls 0x00000000 > > VideoControl Interface Descriptor: > > bLength 11 > > bDescriptorType 36 > > bDescriptorSubtype 5 (PROCESSING_UNIT) > > Warning: Descriptor too short > > bUnitID 9 > > bSourceID 11 > > wMaxMultiplier 0 > > bControlSize 2 > > bmControls 0x00000000 > > iProcessing 0 > > bmVideoStandards 0x09 > > None > > SECAM - 625/50 > > VideoControl Interface Descriptor: > > bLength 9 > > bDescriptorType 36 > > bDescriptorSubtype 3 (OUTPUT_TERMINAL) > > bTerminalID 8 > > wTerminalType 0x0101 USB Streaming > > bAssocTerminal 0 > > bSourceID 10 > > iTerminal 0 > > VideoControl Interface Descriptor: > > bLength 25 > > bDescriptorType 36 > > bDescriptorSubtype 6 (EXTENSION_UNIT) > > bUnitID 12 > > guidExtensionCode {45b5da73-23c1-4a3d-a368-610f078c4397} > > bNumControl 0 > > bNrPins 1 > > baSourceID( 0) 9 > > bControlSize 0 > > iExtension 0 This extension unit is strange, it exposes no control. > > VideoControl Interface Descriptor: > > bLength 27 > > bDescriptorType 36 > > bDescriptorSubtype 6 (EXTENSION_UNIT) > > bUnitID 10 > > guidExtensionCode {1229a78c-47b4-4094-b0ce-db07386fb938} > > bNumControl 2 > > bNrPins 1 > > baSourceID( 0) 12 > > bControlSize 2 > > bmControls( 0) 0x00 > > bmControls( 1) 0x06 > > iExtension 0 This one exposes two controls, which are likely used to control the IR light. I however suspect that the controls merely expose an indirect way to read/ write internal registers, so we would really need to capture a USB trace when using the device in Windows (assuming that the machine is shipped with software that can control the IR light). [snip] -- Regards, Laurent Pinchart
