260715-ass字幕文件转为rgb与alpha视频

#! pwsh.exe
# ass字幕文件转为rgb与alpha视频
# 在DaVinci中使用时, edit界面中rgb拖入时间线, fusion界面中将alpha视频作为rgb视频的mask输入, 然后调整rgb视频settings-channel为Luminance即可.
# nvenc的av1编码似乎不支持444, 难以理解...
ffmpeg -y -hide_banner `
-i Input.mkv `
-filter_complex "[0:v]format=rgba,colorchannelmixer=rr=0:gg=0:bb=0:aa=0,ass=Input.ass:fontsdir=./font:alpha=1[sub]; `
[sub]split=2[rgb_in][alpha_in]; [rgb_in]format=yuv444p16le[v_rgb]; [alpha_in]alphaextract,format=p010le[v_alpha]" `
-map "[v_rgb]" -c:v hevc_nvenc -profile:v rext -rc vbr -cq 18 -b:v 0 -maxrate 38400k -bufsize 76800k -multipass fullres -preset p7 -tune hq -color_primaries bt709 -color_trc bt709 -colorspace bt709 -map_metadata -1 -map_metadata:s:v -1 -an Output_RGB.mp4 `
-map "[v_alpha]" -c:v hevc_nvenc -profile:v main10 -rc vbr -cq 18 -b:v 0 -maxrate 38400k -bufsize 76800k -multipass fullres -preset p7 -tune hq -map_metadata -1 -map_metadata:s:v -1 -an Output_Alpha.mp4