Thanks a lot for your reply. I'm actually feeding the x264/265 GUI with an avisynth script. I will remove the converttoyv12 line and test this ASAP. ...

Original video files are h264, 8bits.Editing with Vegas (which works with RGB internally if I'm not mistaken) Outputting MagicYUV file from VegasEnco...

Thanks a lot for your reply. As a side question, I always encode my projects by using an external encoder (either x264 or x265) and magicyuv as inter...