Proxies with Alpha channel

Next are some examples of tested and working configurations that maintain the alpha channel:

Proxy #1
	Scale factor: 1/4
	Rescaled to project size (FFMPEG only) = unchecked
	File Format: FFMPEG | qt
	Video Preset-->
		Compression: png.qt
		Bitrate: 0
		Quality: -1
		Pixels: rgba (or rgba64be)
	
	
Proxy #2
	Scale factor: 1/4
	Rescaled to project size (FFMPEG only) = unchecked
	File Format: FFMPEG | qt
	Video Preset-->
		Compression: magicyuv.qt
		Bitrate: 0
		Quality: -1
		Pixels: yuva444p
	
	
Proxy #3
	Scale factor: 1/4
	Rescaled to project size (FFMPEG only) = unchecked
	File Format: FFMPEG | qt
	Video Preset-->
		Compression: openjpeg.qt
		Bitrate: 0
		Quality: -1
		Pixels: yuva420p
	
	
Proxy #4
	Scale factor: 1/4
	Rescaled to project size (FFMPEG only) = unchecked
	File Format: FFMPEG | pro
	Video Preset-->
		Compression: prores_4444.pro
		prores_4444xq.pro
		Bitrate: 0
		Quality: -1
		Pixels: yuva444p10le
	
	
Proxy #5
	Scale factor: 1/4
	Rescaled to project size (FFMPEG only) = unchecked
	File Format: FFMPEG | mkv
	Video Preset-->
		Compression: user_ffvhuff.mkv
		Bitrate: 0
		Quality: -1
		Pixels: yuva4--p
				   yuva4--p--le