About YUV Videos

[VideoFan576]

Let's say I have a short video with YUV 4:4:4 and 10bit depth, and I convert it to a FFV1 with YUV 4:2:0 and 8bit depth. Is the FFV1 lossless? Will the colors be the same?

If so, how do I convert videos while changing the chroma subsampling and bit depth without losing quality and get the right colors?

[pandy]

FFV1 is lossless but conversion from YUV 4:4:4 10b to YUV 4:2:0 8b is lossy - colors can be the same or similar (within 8 bit accuracy) - depends on your YUV 4:4:4 10b source - if your source is 8 bit converted to 10 bit and after back to 8 bit then there is chance that in overall conversion will be lossless.

[jagabo]

Say you have a 1920x1080 YUV 4:4:4 frame. All three channels have 1920x1080 resolution. But when you convert that to YUV 4:2:0 the chroma channels (U and V) are reduced to 960x540. This is a lossy conversion.

https://en.wikipedia.org/wiki/Chroma_subsampling

Here's a sample where 4:4:4 was converted to 4:2:0:
https://forum.videohelp.com/threads/319360-DVD-LAB-PRO-color-map#post1977264

10 bit video has a range of 1024 different values (0 to 1023) for each component (Y, U, and V). Converting that to 8 bits (typically done by dividing the 10 bit values by 4) reduces the range to only 256 different values (0 to 255). That is a lossy conversion.