[Kdenlive-devel] [Mlt-devel] Qt based text producer

[Dan Dennedy]

2009/7/11 Marco Gittler <g.marco at freenet.de>:
>
> Am 10.07.2009 um 23:53 schrieb Dan Dennedy:
>
>> 2009/7/10 Marco Gittler <g.marco at freenet.de>:
>>>
>>> @dan th title should be created with alpha channel.
>>> how can i test in melt  to overlay this title over a video ?
>>
>> Please make sure that your new producer only produces mlt_image_rgb24a
>> and indicates it. Do not worry about conversion to mlt_image_yuv422
>> anymore.
>>
>>> melt kdenlivetitle:try.kdenlivetitle -track video.avi -attach
>>> transition:mix
>>> -> does not work :(
>>
>> add "*.kdenlivetitle=kdenlivetitle" to core/loader.dict
>>
>> melt video.avi -filter watermark:try.kdenlivetitle composite.progressive=1
>
> nice, this works for pixbuf pictures. but with the kdenlivetitle :no overlay
> as standalone prodcuer the titleplayer works very well.
>
> does mlt_image_rgb24a, also include (like the name seems to say) the alpha
> channel ?

Yes.

> it seems the alpha will not be set.

If you return mlt_image_rgb24a and do not include the alpha channel
byte per pixel, then the image will skewed because downstream
functions expect 4 bytes per pixel. Producer qimage supports this, but
it must convert ARGB to RGBA. Maybe something in the way you render is
writing alpha channel byte as 0xff.

> or must i copy the alpha channel to an extra buffer and set this then to
> "alpha" as property ?

This is possible, but it only makes sense if the alpha channel is a
separate picture, which is not typical for Qt.

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