I’m a little bit confused…
According to several reference sites, CRF=0 is true lossless (in the same color space).
https://trac.ffmpeg.org/wiki/Encode/H.264 said:
The range of the CRF scale is 0–51, where 0 is lossless
https://www.oodlestechnologies.com/blogs/H.264-Basics-%3A-CRF-Guide said:
0 is lossless (Lower the value, higher is the quality)
https://forum.videohelp.com/threads/358901-is-x264lossless-really-lossless said:
Yes it’s truly lossless in the same colorspace
(…)
When people talk about “lossless” codecs in terms of video, it refers to the decoded output. So the decoded output of say, a lagarith lossless encode in YUV 4:2:0 will be the same as the decoded output of x264 crf0 YUV 4:2:0 using intra only, or the decoded output of x264 crf0 YUV 4:2:0 long GOP + some slower settings. The only difference in terms of quality will be the last one will be smaller in filesize . The decoded output and uncompressed filesize will be exactly the same for all 3