[gst-devel] Need help using gst-launch to display a PNG image, Part 3+

[Bill West]

Hi All,

I followed Tim's advice on using gst-launch to display a PNG file, and
Luciana's fix for getting my PNG to "mix" with a video stream (thanks again
to you both), but doing that, I discovered that the PNG file, which has a
transparent alpha component, is showing opaque, so the video never shows
thru.  (I know it's there though, 'cause if I draw the video on top of the
PNG instead of underneath it, it shows fine.

The command I'm using is:

gst-launch-0.10 filesrc location=overlay.png ! pngdec ! ffmpegcolorspace !
videoscale ! imagefreeze ! videomixer name=mix ! autovideosink  videotestsrc
! video/x-raw-yuv, width=320, height=240 ! mix.

Looking at the documentation, the only possible solution I could find is an
element called "alphacolor", but nowhere placed in the pipeline does it
work, so I'm stumped again.

So, that's my main question:  how to I get a PNG file WITH transparent
sections to properly render?

And, if I could ask a few more questions, I'd appreciate it (my boss says
I'm taking too long at this :)...

2.  we have ALSA audio, and I see there's an element called "alsasink",
though I couldn't find much documentation on it.  Is there a way with
alsasink to specify the output channel?  (our card has 8, so 4 stereo
pairs).

3.  Is there a way to have the other PNG images fade in and fade out of the
window to/from black?

4.  Is there a way to loop between two particular frames on a video?

5.  Is videobox the best way to position my video behind the overlay PNG?  I
got it to work kind of, but there were artifacts, like everything to the
left and above the video is black.

6.  I thought someone must have written a translator that takes a gst-launch
command line and converts it to the equivalent C code, but couldn't find
one.  Did I just not look in the right place?

Sorry for the pile of questions, but as I say, the heat is on, and these are
all problems I'd better solve soon, or I'm back to using straight X11 and
OpenGL, and I guess libxine to pull apart my video into frames.

Thanks, thanks, thanks!

Bill.
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