"“lossless” in Shotcut export does not imply the image goes through the engine untouched. It simply means that the codec is lossless or in lossless mode. The engine does not support every pixel format and color space in existence – only a few. Often sources get converted going through the engine. In your case, the source is RGB, but the engine defaults to yuv422 unless it has an mlt_image_format specified in Export > Other. For your 6SrK4.mp4, you would need mlt_image_format=rgb24 Also, in order to avoid image changes, you must use a Video Mode that matches the source and must not use any effecs (multiple video tracks, transitions, filters). (A mismatching video mode can cause automatic deinterlace, colorspace conversion, scaling, and padding)."
–source: https://forum.shotcut.org/t/lossless-annoyances/18344
"“lossless” in Shotcut export does not imply the image goes through the engine untouched. It simply means that the codec is lossless or in lossless mode. The engine does not support every pixel format and color space in existence – only a few. Often sources get converted going through the engine. In your case, the source is RGB, but the engine defaults to yuv422 unless it has an mlt_image_format specified in Export > Other. For your 6SrK4.mp4, you would need mlt_image_format=rgb24 Also, in order to avoid image changes, you must use a Video Mode that matches the source and must not use any effecs (multiple video tracks, transitions, filters). (A mismatching video mode can cause automatic deinterlace, colorspace conversion, scaling, and padding)." –source: https://forum.shotcut.org/t/lossless-annoyances/18344