Overlay Video with Alpha Parts on Video

Help/How To
1

Hi,

I apologise if this is covered simply somewhere but I have searched and read all related topics and cannot find a concise answer.

I wish to use a video with Alpha elements (say title simple text with alpha background). I have tried multiple codec conversions through ffmpeg - to png, prores and others but it’s still just black background. The files are .mov files. Note I have one clip that works and it is ProRes codec.

Tried:

  • Changing track blend to “over” for example doesn’t work
  • Applying filters such as Opacity is not effective as it makes the non alpha areas transparent)

I am either not converting into a usable codec or i’m missing something simple?

Please help.

Thanks in advance…

Lee

2

Are you batch-converting existing videos with ffmpeg, or are you wanting to create new videos in Shotcut? I couldn’t figure out the end goal.

Assuming that your goal is to create Text: Simple title videos in Shotcut for use elsewhere, a reliable way to export with an alpha channel is to go to the Export panel, choose the Intermediate > ProRes preset, click the Advanced button, go to the Other tab, and make it contain the following lines:

mlt_image_format=rgb24a
pix_fmt=yuva444p10le
vprofile=4444
vendor=apl0
movflags=+write_colr+faststart

Then export as usual. No special blend modes or filters have to be used on the video tracks. Any video area that doesn’t have pixel data defined will default to transparent alpha.

If you are trying to import video that has an alpha channel, nothing special should have to be done. It should just work. Going to the Properties panel for that clip will determine if the video format is truly an alpha format (like yuva or rgb24a). If it isn’t an alpha format, then it would take a chroma key or similar filter to knock out the background.

3

Why are you doing this? Why not use the file directly in Shotcut? If it does not work, then post the media info of the file.

4

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