On Sun, 15 Feb 2009, Hans de Goede wrote: > Hans Verkuil wrote: > > On Sunday 15 February 2009 10:08:04 Hans de Goede wrote: > >> kilgota@xxxxxxxxxxxxxxxxxxxxxx wrote: > >>> On Sat, 14 Feb 2009, Hans Verkuil wrote: > >>>> On Saturday 14 February 2009 22:55:39 Hans de Goede wrote: > >>>>> Adam Baker wrote: > >>>> OK, make it a buffer flag. I've got to agree that it makes more sense > >>>> to do > >>>> it that way. > >>>> > >>> The most particular problem is that some of the cameras require byte > >>> reversal of the frame data string, which would rotate the image 180 > >>> degrees around its center. Others of these cameras require reversal of > >>> the horizontal lines in the image (vertical 180 degree rotation of the > >>> image across a horizontal axis). > >>> > >>> The point is, one can not tell from the Vendor:Product number which of > >>> these actions is required. However, one *is* able to tell immediately > >>> after the camera is initialized, which of these actions is required. > >>> Namely, one reads and parses the response to the first USB command sent > >>> to the camera. > >> Ack, but the problem later was extended by the fact that it turns out > >> some cams have a rotation detection (gravity direction) switch, which > >> means you can flip the cam on its socket while streaming, and then the > >> cam will tell you its rotation has changed, that makes this a per frame > >> property rather then a static property of the cam. Which lead to this > >> discussion, but we (the 2 Hans 's) agree now that using the flags field > >> in the buffer struct is the best way forward. So there is a standard now, > >> simply add 2 buffer flags to videodev2.h, one for content is h-flipped > >> and one for content is v-flipped and you are done. > > > > I think we should also be able to detect 90 and 270 degree rotations. Or at > > the very least prepare for it. It's a safe bet to assume that webcams will > > arrive that can detect portrait vs landscape orientation. > > Handling those (esp on the fly) will be rather hard as width and height then > get swapped. So lets worry about those when we need to. We will need an > additional flag for those cases anyways. Why would you need to worry about width and height getting swapped? Meta-data about the frame would indicate it's now in portrait mode vs landscape mode, but the dimentions would be unchanged. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
