AYUV text overlay

[Lane Brooks]

Sebastian,

Looking through the git log, it looks like you added support for the
AYUV format in the pango textoverlay element.

It does not quite behave how I was hoping it would, so I wanted to
discuss it with you to understand the current implementation.

If I create a completely transparent background image, I was hoping that
textoverlay would still overlay the requested text appropriately, but
the current implementation leaves the resulting image (including the
text overlay) completely transparent (so the text is invisible). You can
see this by running this pipeline:

gst-launch videotestsrc pattern=white !
video/x-raw-yuv,format=\(fourcc\)AYUV ! alpha alpha=0.0 ! textoverlay
text=Testing auto-resize=False font-desc=60px ! videomixer !
ffmpegcolorspace ! autovideosink

Attached is a patch that changes the alpha compositing behavior to use a
"A OVER B" scheme (http://en.wikipedia.org/wiki/Alpha_compositing).  Can
you comment on this approach? With this patch, the above pipeline works
like I want it to in that the text overlays and is visible regardless of
alpha of the background image. I am not sure, however, the reasons for
the current implementation and what advantages it has.

In case there is confusion, if you run the above pipeline with and
without this patch, you will instantly see the difference. Without this
patch, you get a completely transparent image and the text overlay is
invisible. With the patch you get a transparent image everywhere except
for the text in the overlay.

If the behavior from this patch is considered the appropriate behavior,
I can also fix the the RGBA/ABGR path to do the same thing.

Thanks,
Lane



------------------------------------------------------------------------------
Gaining the trust of online customers is vital for the success of any company
that requires sensitive data to be transmitted over the Web.   Learn how to
best implement a security strategy that keeps consumers' information secure
and instills the confidence they need to proceed with transactions.
http://p.sf.net/sfu/oracle-sfdevnl 
_______________________________________________
gstreamer-devel mailing list
[hidden email]
https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

[Tim-Philipp Müller-2]

On Mon, 2011-01-10 at 23:31 -0700, Lane Brooks wrote:

Hi Lane,

> [textoverlay] does not quite behave how I was hoping it would (...)
>
> If I create a completely transparent background image, I was hoping that
> textoverlay would still overlay the requested text appropriately, but
> the current implementation leaves the resulting image (including the
> text overlay) completely transparent (so the text is invisible). (...)
>
> Attached is a patch that changes the alpha compositing behavior (...)

Please could you open a bug for this in bugzilla and attach your patch
there, so it doesn't get overlooked? Thanks!

http://gstreamer.freedesktop.org/bugs/

Cheers
-Tim



------------------------------------------------------------------------------
Gaining the trust of online customers is vital for the success of any company
that requires sensitive data to be transmitted over the Web.   Learn how to
best implement a security strategy that keeps consumers' information secure
and instills the confidence they need to proceed with transactions.
http://p.sf.net/sfu/oracle-sfdevnl 
_______________________________________________
gstreamer-devel mailing list
[hidden email]
https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

[Lane Brooks]

On 01/11/2011 02:13 AM, Tim-Philipp Müller wrote:

> On Mon, 2011-01-10 at 23:31 -0700, Lane Brooks wrote:
>
> Hi Lane,
>
>> [textoverlay] does not quite behave how I was hoping it would (...)
>>
>> If I create a completely transparent background image, I was hoping that
>> textoverlay would still overlay the requested text appropriately, but
>> the current implementation leaves the resulting image (including the
>> text overlay) completely transparent (so the text is invisible). (...)
>>
>> Attached is a patch that changes the alpha compositing behavior (...)
>
> Please could you open a bug for this in bugzilla and attach your patch
> there, so it doesn't get overlooked? Thanks!
>

I am happy to file a bug with this patch. Is bugzilla where you prefer
the discussion take place on what the desired overlay behavior should
be? In other words, I am not sure the reasons and advantages of the
current implementation, so I wanted to first understand that prior to
seeking the application of my patch.

Lane

------------------------------------------------------------------------------
Gaining the trust of online customers is vital for the success of any company
that requires sensitive data to be transmitted over the Web.   Learn how to
best implement a security strategy that keeps consumers' information secure
and instills the confidence they need to proceed with transactions.
http://p.sf.net/sfu/oracle-sfdevnl 
_______________________________________________
gstreamer-devel mailing list
[hidden email]
https://lists.sourceforge.net/lists/listinfo/gstreamer-devel