On 11/24/2011 01:06 PM, 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: >>>>>> 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). I'm not sure if it was the intention. If pixel format has alpha component this control would set per-pixel alpha to an arbitrary control value. If the pixel format doesn't have alpha, then what this control would do - I'm not sure. > >> 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 More precisely it sets a per-pixel alpha to some arbitrary value. For instance in this case the A value for each pixel with ARGB8888 pixel format would be 128. > 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 ? Although V4L2_CID_GLOBAL_ALPHA sounds good, V4L2_CID_ALPHA_COMPONENT reflects more precisely what was my intention. The control was supposed to set the alpha component for ARGB formats. -- Regards, Sylwester -- 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
