Hi Deva,
For one of our ongoing projects, I've been trying to get alpha
blending work in Android on OMAP3EVM. For this we have implemented a simple
Activity in Android that plays a video (on the video1 plane) and displays an
image on the GFX plane. The image is rendered using drawable with some
specific alpha value (to control transparency) . When this app is tested on
the emulator as well as G1 phone (running Android Eclair), we were to see
the expected output (video is viewable through transparent image).
However while testing the same app on OMAP3EVM running Android
(Eclair), the alpha blending never works. We are not able to see the
underlying video plane at all (only the image gets displayed). Based on the
discussion on this thread, I've looked at the liboverlay implementation in
"hardware/ti/omap3/" folder. Apparently by default, LOCAL_ALPHA is disabled
and the GLOBAL_ALPHA value is set to 255 (opaque ??). I've modified the code
to enable LOCAL_ALPHA as well as GLOBAL_ALPHA with some lesser value (100)
and executed the Android activity, but the result is the same.
Since I was not able to do this programmatically, I've tried the
omapdss sysfs entries to manipulate alpha values. The following commands are
issued:
echo "1" > /sys/devices/platform/omapdss/manager0/alpha_blending_enabled
echo "100" > /sys/devices/platform/omapdss/overlay0/global_alpha
Now the applications shows transparent image and video playback underneath.
Some quetsions based on these observations:
1. Is the liboverlay implementation incomplete as far as "color-keying" and
"alpha-blending" are concerned?
2. When I went through the v4l2 code for omap-vout, I do see a comment that
the "global_alpha" is always 255 and cannot be changed. Is this
understanding correct? If so "how did it work when I've set the global_alpha
value using sysfs entry?
3. Do you any specific technical input on "how to get this working with
Android"
4. Is local alpha tested on OMAP3530? Any clues?
I know I'm firing a lot questions. It would be great if we could have some
discussions on these points as well.
Warm Regards,
Anil
On Mon, May 10, 2010 at 4:52 PM, Deva R <[email protected]> wrote:
> hi,
>
> i havent tried per fb or video device level., but should be possible..
>
> can you check with local alpha flags, local to framebuffer and overlay
> devices?
> V4L2_FBUF_FLAG_LOCAL_ALPHA, V4L2_FBUF_FLAG_LOCAL_INV_ALPHA
>
>
> On Mon, May 10, 2010 at 12:37 PM, Svetozar Miuchin
> <[email protected]> wrote:
> > Yes, but what I need to do is make all of the Android's surfaces
> > beneath (and including) the video surface transparent, but leave the
> > global alpha as is for the possible player's media controls. Any
> > ideas?
> >
> > On May 6, 5:20 pm, Deva R <[email protected]> wrote:
> >> you can chose the transparency level by tuning alpha blend..
> >>
> >> on enabling global alpha blending, the final ouptput pixel will be
> arrived as,
> >> output = (framebuffer pixel * alpha + video pixel * (255 - alpha)) /
> 255
> >>
> >> you need to set this alpha field with below ioctl commands..
> >>
> >> ret = v4l2_ioctl(fd, VIDIOC_G_FMT, &fmt);
> >> fmt.fmt.win.global_alpha = alpha & 0xFF;
> >> ret = v4l2_overlay_ioctl(fd, VIDIOC_S_FMT, &fmt);
> >>
> >> you can check complete source in our tree -
> http://git.omapzoom.org/?p=platform/hardware/ti/omap3.git;a=blob;f=li...
> >>
> >> On Thu, May 6, 2010 at 7:55 PM, Svetozar Miuchin
> >>
> >>
> >>
> >> <[email protected]> wrote:
> >> > You mean setting the global alpha to fully transparent? If so, I've
> >> > thought about that, but that destroys the possibility of having on-
> >> > screen media controls.. Right?
> >>
> >> > On May 6, 4:18 pm, Deva R <[email protected]> wrote:
> >> >> You can enable alpha blending in your display driver, so both
> graphics
> >> >> and video overlay blend..
> >>
> >> >> my call sequence for this are like (get fb handle, toggle alpha
> >> >> blending, set the fb options)
> >>
> >> >> v4l2_ioctl(fd, VIDIOC_G_FBUF, &fbuf);
> >> >> fbuf.flags |= V4L2_FBUF_FLAG_GLOBAL_ALPHA;
> >> >> v4l2_ioctl(fd, VIDIOC_S_FBUF, &fbuf);
> >>
> >> >> more info:http://v4l2spec.bytesex.org/spec/r10595.htm-> framebuffer
> flags ->
> >> >> V4L2_FBUF_FLAG_GLOBAL_ALPHA
> >>
> >> >> On Thu, May 6, 2010 at 7:20 PM, Svetozar Miuchin
> >>
> >> >> <[email protected]> wrote:
> >> >> > Hi,
> >> >> > I'm porting Android to a board with hardware video decoding
> support.
> >> >> > The board hardware draws the video into a video layer beneath the
> >> >> > graphic layer. I've implemented a custom media player that passes
> the
> >> >> > calls to the hardware decoders, but I need to make Android's
> surfaces
> >> >> > transparent. Is there any way this is possible with the current
> >> >> > Android architecture? I'm using the Eclair version for MIPS
> >> >> > architectures.
> >> >> > Thanks in advance,
> >> >> > Svetozar
> >>
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