ffmpeg convert from H.264 (High 4:4:4 Profile) to H.265 (Main Profile)

Question

How can I convert a video from H.264 (High 4:4:4 Profile) to H.265 (Main Profile 4:2:0) using ffmpeg?

I can't do that with this command: ffmpeg -i input.mkv -c:v hevc_nvenc -c:a copy output2.mkv

That'd return an error, does not recognize the source format

Answer 1

Get an error:

Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> hevc (libx265))
Stream #0:1 -> #0:1 (copy)
Stream #0:3 -> #0:2 (subrip (srt) -> ass (ssa))
Press [q] to stop, [?] for help
[h264 @ 0000019d020a5000] gray chroma
[h264 @ 0000019d020a5000] error while decoding MB 61 26, bytestream 388357
[h264 @ 0000019d020a5000] concealing 5028 DC, 5028 AC, 5028 MV errors in I frame
[libx265 @ 0000019d020a8340] Error setting preset/tune 'placebo'/(null).
[libx265 @ 0000019d020a8340] Possible presets: ultrafast superfast veryfast 
faster fast medium slow slower veryslow placebo
[libx265 @ 0000019d020a8340] Possible tunes: psnr ssim grain zerolatency 
fastdecode animation
Error initializing output stream 0:0 -- Error while opening encoder for output 
stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!