Hi Hans, 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: > > >>> This control is intended for video capture or memory-to-memory > > >>> devices that are capable of setting up the alpha conponent to > > >>> some arbitrary value. > > >>> The V4L2_CID_COLOR_ALPHA control allows to set the alpha channel > > >>> globally to a value in range from 0 to 255. > > >>> > > >>> Signed-off-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx> > > >>> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > > >>> --- > > >>> > > >>> Documentation/DocBook/media/v4l/controls.xml | 20 > > >>> ++++++++++++++------ .../DocBook/media/v4l/pixfmt-packed-rgb.xml > > >>> > > >>> | 7 +++++-- drivers/media/video/v4l2-ctrls.c | > > >>> > > >>> 7 +++++++ include/linux/videodev2.h | 6 > > >>> +++--- 4 files changed, 29 insertions(+), 11 deletions(-) > > >>> > > >>> diff --git a/Documentation/DocBook/media/v4l/controls.xml > > >>> b/Documentation/DocBook/media/v4l/controls.xml index 3bc5ee8..7f99222 > > >>> 100644 > > >>> --- a/Documentation/DocBook/media/v4l/controls.xml > > >>> +++ b/Documentation/DocBook/media/v4l/controls.xml > > >>> @@ -324,12 +324,6 @@ minimum value disables backlight > > >>> compensation.</entry> > > >>> > > >>> (usually a microscope).</entry> > > >>> > > >>> </row> > > >>> <row> > > >>> > > >>> - <entry><constant>V4L2_CID_LASTP1</constant></entry> > > >>> - <entry></entry> > > >>> - <entry>End of the predefined control IDs (currently > > >>> -<constant>V4L2_CID_ILLUMINATORS_2</constant> + 1).</entry> > > >>> - </row> > > >>> - <row> > > >>> > > >>> <entry><constant>V4L2_CID_MIN_BUFFERS_FOR_CAPTURE</constant></e > > >>> ntry > > >>> > > >>> > <entry>integer</entry> > > >>> > > >>> <entry>This is a read-only control that can be read by the > > >>> application > > >>> > > >>> @@ -345,6 +339,20 @@ and used as a hint to determine the number of > > >>> OUTPUT buffers to pass to REQBUFS. > > >>> > > >>> The value is the minimum number of OUTPUT buffers that is necessary > > >>> for hardware to work.</entry> > > >>> > > >>> </row> > > >>> > > >>> + <row id="v4l2-color-alpha"> > > >>> + <entry><constant>V4L2_CID_COLOR_ALPHA</constant></entry> > > >>> + <entry>integer</entry> > > >>> + <entry> Sets the color alpha component on the capture device. > > >>> It is + applicable to any pixel formats that contain the alpha > > >>> component, + e.g. <link linkend="rgb-formats">packed RGB image > > >>> formats</link>. + </entry> > > > > > > As the alpha value is global, isn't it applicable to formats with no > > > alpha component as well ? > > > > Hmm, I can't say no.. The control was intended as a means of setting up > > the alpha value for packed RGB formats: > > http://linuxtv.org/downloads/v4l-dvb-apis/packed-rgb.html#rgb-formats > > > > However it could well be used for formats with no alpha. Do you think > > the second sentence above should be removed or should something else be > > added to indicate it doesn't necessarily have to have a connection > > with ARGB color formats ? I think we should make it explicit that this global alpha value is applied in addition to a possibly per-pixel alpha value (if available in the selected format). > Huh? How can this be used for formats without an alpha channel? If my understanding is correct, this control sets a global alpha value for the whole overlay. For instance, with V4L2_CID_COLOR_ALPHA set to 0.5, an overlay using a non-alpha format (such as YUYV), or an overlay using an alpha format with the alpha value set to 1 for every pixel, would be half transparent. In other words, the resulting alpha value is the product of the global alpha value and the per-pixel alpha value. Non-alpha formats have an implicit per- pixel alpha value equal to 1 for every pixel. > > >>> + </row> > > >>> + <row> > > >>> + <entry><constant>V4L2_CID_LASTP1</constant></entry> > > >>> + <entry></entry> > > >>> + <entry>End of the predefined control IDs (currently > > >>> + <constant>V4L2_CID_COLOR_ALPHA</constant> + 1).</entry> > > >>> + </row> > > >>> > > >>> <row> > > >>> > > >>> <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry> > > >>> <entry></entry> > > >>> > > >>> diff --git a/Documentation/DocBook/media/v4l/pixfmt-packed-rgb.xml > > >>> b/Documentation/DocBook/media/v4l/pixfmt-packed-rgb.xml index > > >>> 4db272b..da4c360 100644 > > >>> --- a/Documentation/DocBook/media/v4l/pixfmt-packed-rgb.xml > > >>> +++ b/Documentation/DocBook/media/v4l/pixfmt-packed-rgb.xml > > >>> @@ -428,8 +428,11 @@ colorspace > > >>> <constant>V4L2_COLORSPACE_SRGB</constant>.</para> > > >>> > > >>> <para>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 > > >>> > > >>> -<link linkend="overlay">Video Overlay</link> or <link > > >>> -linkend="osd">Video Output Overlay</link>.</para> > > >>> +<link linkend="overlay">Video Overlay</link> or <link linkend="osd"> > > >>> +Video Output Overlay</link> or when global alpha has been configured > > >>> +for a <link linkend="capture">Video Capture</link> by means of > > >>> +<link linkend="v4l2-color-alpha"> <constant>V4L2_CID_COLOR_ALPHA > > >>> +</constant> </link> control.</para> > > >>> > > >>> <example> > > >>> > > >>> <title><constant>V4L2_PIX_FMT_BGR24</constant> 4 × 4 > > >>> pixel > > >>> > > >>> diff --git a/drivers/media/video/v4l2-ctrls.c > > >>> b/drivers/media/video/v4l2-ctrls.c index 5552f81..bd90955 100644 > > >>> --- a/drivers/media/video/v4l2-ctrls.c > > >>> +++ b/drivers/media/video/v4l2-ctrls.c > > >>> @@ -466,6 +466,7 @@ const char *v4l2_ctrl_get_name(u32 id) > > >>> > > >>> case V4L2_CID_ILLUMINATORS_2: return "Illuminator 2"; > > >>> case V4L2_CID_MIN_BUFFERS_FOR_CAPTURE: return "Minimum Number of > > >>> Capture Buffers"; case V4L2_CID_MIN_BUFFERS_FOR_OUTPUT: return > > >>> "Minimum Number of Output Buffers"; > > >>> > > >>> + case V4L2_CID_COLOR_ALPHA: return "Color Alpha"; > > >> > > >> I prefer CID_ALPHA_COLOR and string "Alpha Color". I think it is more > > >> natural than the other way around. > > > > OK, I guess you're right. And Google returns about twice as many hits for > > "alpha color" than for "color alpha"... > > > > > I'm not too found of "color" in the name. Is the alpha value considered > > > as a color ? > > > > Certainly it isn't, but Alpha alone looks a bit odd. It's too generic > > IMHO. > > How about V4L2_CID_ALPHA_COMPONENT? Or V4L2_CID_GLOBAL_ALPHA ? -- 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
