While encoder parameters for lossless encoding are set correctly, output is not lossless due to pixel format being set to `AV_PIX_FMT_YUV420P` which is inherently lossy due to chroma subsampling. This was reported in T61569 and was merged to T57397, but there were 2 bugs - one for encoding and one for decoding. Set pixel format to `AV_PIX_FMT_YUV444P` when rendering lossless H264 files. This format isn't available in `codec->pix_fmts[0]` and it looks, that it has to be hard-coded. Reviewed By: sergey Differential Revision: D11458