Hi Sylwester, On Thursday 24 November 2011 16:53:12 Sylwester Nawrocki wrote: > On 11/24/2011 03:00 PM, Laurent Pinchart wrote: > > On Thursday 24 November 2011 13:22:10 Hans Verkuil wrote: > >> On Thursday, November 24, 2011 13:06:09 Laurent Pinchart wrote: > >>> On Thursday 24 November 2011 12:49:00 Hans Verkuil wrote: > >>>> On Thursday, November 24, 2011 12:39:54 Sylwester Nawrocki wrote: > >>>>> On 11/24/2011 12:09 PM, Laurent Pinchart wrote: > >>>>>> On Thursday 24 November 2011 12:00:45 Hans Verkuil wrote: > >>>>>>> On Thursday, November 24, 2011 11:53:16 Sylwester Nawrocki wrote: > >> Well, if that's the case, then we already have an API for that > >> (http://hverkuil.home.xs4all.nl/spec/media.html#v4l2-window, field > >> global_alpha). > >> > >> It was my understanding that this is used with a mem2mem device where > >> you just want to fill in the alpha channel to the desired value. It's > >> not used inside the device at all (that happens later in the pipeline). > > > > OK, now I understand. Maybe the documentation should describe this a bit > > more explicitly ? > > I've modified the control description so now it is: > > V4L2_CID_ALPHA_COMPONENT > integer > What about clarifying it further with something like "When a mem-to-mem device produces a frame format that includes an alpha component (e.g. _packed RGB image_ formats), the alpha value is not defined by the mem-to-mem input data. This control lets you select the alpha component value of all pixels in such a case. It is applicable to any pixel format that contains an alpha component." > And the part below Table 2.6 > > Bit 7 is the most significant bit. The value of a = alpha bits is undefined > when reading from the driver, ignored when writing to the driver, except > when alpha blending has been negotiated for a Video Overlay or Video > Output Overlay or when alpha component has been configured for a Video > Capture by means of V4L2_CID_ALPHA_COMPONENT control. -- Regards, Laurent Pinchart -- 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
