[linux-uvc-devel] Combining interlaced images

[James Fidell]

This may be borderline off-topic for which I apologise, but I know of
no other source of UVC knowledge that I can ask.

I have a camera that I'm trying to get to work which is almost, but not
entirely UVC-compliant as far as I can tell. The only non-compliance I
can find is that it claims a "vendor-specific" class rather than the
expected video class.

I have reached the point where I can get video from the camera, but
I'm unsure of how to interpret the interlacing flags in the video
descriptor and I've been able to turn up any explanation via google.
The UVC specification doesn't seem particularly helpful in this respect
either. This is what I believe are the relevant parts of the
descriptor set:

VideoStreaming Interface Descriptor:
bLength 27
bDescriptorType 36
bDescriptorSubtype 4 (FORMAT_UNCOMPRESSED)
bFormatIndex 1
bNumFrameDescriptors 2
guidFormat
{59555932-0000-1000-8000-00aa00389b71}
bBitsPerPixel 16
bDefaultFrameIndex 1
bAspectRatioX 0
bAspectRatioY 0
bmInterlaceFlags 0x00
Interlaced stream or variable: No
Fields per frame: 2 fields
Field 1 first: No
Field pattern: Field 1 only
bCopyProtect 0
VideoStreaming Interface Descriptor:
bLength 30
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 1
bmCapabilities 0x00
Still image unsupported
wWidth 640
wHeight 960
dwMinBitRate 3809017920
dwMaxBitRate 3809017920
dwMaxVideoFrameBufferSize 5111808
dwDefaultFrameInterval 333333
bFrameIntervalType 1
dwFrameInterval( 0) 333333
VideoStreaming Interface Descriptor:
bLength 30
bDescriptorType 36
bDescriptorSubtype 5 (FRAME_UNCOMPRESSED)
bFrameIndex 2
bmCapabilities 0x00
Still image unsupported
wWidth 640
wHeight 960
dwMinBitRate 3809017920
dwMaxBitRate 3809017920
dwMaxVideoFrameBufferSize 5111808
dwDefaultFrameInterval 333333
bFrameIntervalType 1
dwFrameInterval( 0) 333333


Can anyone explain what the bmInterlaceFlags "Interlaced stream or
variable" and "Field pattern" mean?

Also, the vendor claims the camera is 1280x960, but the width and height
values give 640x960. I might have expected 1280x480 for an interlaced
field. Is there an explanation for the size being 640x960?

Thanks,
James

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[James Fidell]

Post by James Fidell
This may be borderline off-topic for which I apologise, but I know of
no other source of UVC knowledge that I can ask.

Ignore this. I've cracked it :)

James


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