qtblend transition speedup: request original source format instead of consumer format first to avoid unnecessary yuv->rgba conversions
qtblend transition speedup: request original source format instead of consumer format first to avoid unnecessary yuv->rgba conversions

j-b-m/mlt,mltframework/mlt,mltframework/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,mltframework/mlt,mltframework/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,j-b-m/mlt,mltframework/mlt,j-b-m/mlt