[gst-devel] Video mixing problems

[Brandon Lewis]

On Tue, 2010-05-04 at 20:42 +0200, Josep Creus Portolés wrote:
> Hello there,
> 
> We are going to use Premier if I cannot solve this. I don't want it.
> I'm trying to use videomixer, videoscale, videobox and ffdeinterlace to 
> compose a video beginning with tree streams.
> 
> This is the actual script, obviously the xvimagesink filter is 
> substituted by a codec compressor filter.
> 
> gst-launch-0.10 filesrc location="video1.mpg" \
> { ! decodebin2 ! ffdeinterlace ! queue2 ! videocrop left=6 right=8 top=2 
> bottom=6 ! videoscale method=2 ! video/x-raw-yuv, width=454, height=358 
> ! videobox border-alpha=0 alpha=1 right=-266 top=-124 bottom=-94 ! 
> ffmpegcolorspace ! videomixer name=mix ! xvimagesink } \
> { filesrc location="video2.mpg" ! decodebin2 ! ffdeinterlace ! queue2 ! 
> videocrop left=6 right=8 top=2 bottom=6 ! videoscale method=2 ! 
> video/x-raw-yuv, width=268, height=224 ! videobox border-alpha=0 alpha=1 
> left=-452 top=-138 bottom=-214 ! ffmpegcolorspace ! mix. } \
> { multifilesrc location="backgorund.png" num-buffers=102959 ! image/png, 
> framerate=25/1 ! pngdec ! queue2 ! ffmpegcolorspace ! mix. }
> 
> AFAIK, ffdeinterlace only works with I420 colorspace, videocrop, 
> videoscale and videobox has no problem working with it, but it seams 
> that there is no alpha channel, and that makes the chain unusable, only 
> the second video stream is visible with all black bars around. Any ideas 
> on how can I solve this? I've tried using alpha filter, but then the 
> chain is not prerolling at all, whichever method I choose.

videobox has border-alpha and alpha properties and will output AYUV or
ARGB if you tell it to. You may need to insert a caps filter between
videobox and videomixer. You should also look into the alpha and
alphacolor elements.

> 
> Besides that, I don't see GStreamer using the format property at all, 
> how has it to be entered? In GStreamer 0.8 it was something like 
> format=/fourcc/
> 
> And videobox 0.10.16 is supposed to have the autocrop properties, 
> GStreamer web documentation says so, but it have not. To whom I have to 
> report this?
> 
> Oh! I almost forget it, I'm using Ubuntu 9.10.

This shipped with a fairly old gstreamer. See our developer's PPA for
more up-to-date packages.
> 
> Greetings and thanks in advance for any help.
> Josep
> 
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