On Thursday, November 24, 2011 13:06:09 Laurent Pinchart wrote: > 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. 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). Regards, Hans > > > >>> + </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 ? > > -- 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
