FFMPEG - Merging Videos with Transparency

Question

I am trying to merge two videos together, both have transparency, using the command

ffmpeg.exe -i person2.mov -vf \"[in] scale=iw/2:ih/2,fade=out:300:30:alpha=1, pad

Answer 1

You did not specify a video codec for the output, so it is using the default video codec for .mov files which is H.264 (libx264 encoder). However H.264 does not support an alpha channel. If you want transparency in your output video you will need to specify an output video codec that supports an alpha channel, such as the one used for your input, i.e. QuickTime Animation RLE (qtrle). To do this, add the option -c:v qtrle before the output file name. Another codec that supports an alpha channel and can be stored in .mov files is png.

You can check the list of encoders supported by your ffmpeg with ffmpeg -encoders. A command like ffmpeg -h encoder=qtrle will list information specific to that encoder, including the supported pixel formats. A pixel format that includes the string argb, rgba, abgr, bgra, gbra, or yuva has an alpha channel.