How to use the concat to concatenate video files with alpha channel

[christianNeil]

Hello,I am a beginner of Gstreamer. 
I have a problom when I use the 'concat' to concatenate three .mp4 files,the
A.mp4, B.mp4 and C.mp4.
the B.mp4 with a aplha channel.
the A.mp4 and C.mp4 without a aplha channel.


there is my command:
gst-launch-1.0 concat name=c ! queue ! videoconvert !
video/x-raw,format=Y444 !x264enc! qtmux !filesink location=output.mp4  \
filesrc location=a.mp4 ! decodebin ! videoscale
!video/x-raw,width=1280,height=720 ! c. \
filesrc location=b.mp4 ! decodebin ! videoscale
!video/x-raw,width=1280,height=720 ! c. \
filesrc location=c.mp4 ! decodebin ! videoscale
!video/x-raw,width=1280,height=720 ! c.

When I executing this ,I got an error message:
ERROR: from element
/GstPipeline:pipeline0/GstDecodeBin:decodebin1/GstQTDemux:qtdemux0: Internal
data stream error.
Additional debug info:
../gst/isomp4/qtdemux.c(6605): gst_qtdemux_loop ():
/GstPipeline:pipeline0/GstDecodeBin:decodebin1/GstQTDemux:qtdemux0:
streaming stopped, reason not-negotiated (-4)

I don't understand, where did I go wrong?

please help me,
looking forward to your reply .



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