Hi Sylwester, On Friday 25 November 2011 14:24:47 Sylwester Nawrocki wrote: > On 11/25/2011 01:57 PM, Laurent Pinchart wrote: > > 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." > > Thanks for the help. Since there are also mem-to-mem devices that account > an input alpha when producing an output frame (e.g. S5P SoC G2D IP block > supports alpha blending), I would change that to: > > > "When a mem-to-mem device produces a frame format that includes an alpha > component (e.g. _packed RGB image_ formats) and 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. It is applicable to any pixel format > that contains an alpha component." That sounds good to me. > > OR > > "When data format of a frame produced by a mem-to-mem device includes an > alpha component (e.g. _packed RGB image_ formats) and 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. The control is applicable to any > pixel format that contains an alpha component." > > How do you think ? > > >> 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
