Convert 4k to 1080 (no change in codec)

ffmpeg -i input4kvid.mp4 -vf scale=1920:1080 -c:a copy output1080vid.mp4

Convert h.264 to h.265 (no change in resolution)

ffmpeg -i input.mp4 -c:v libx265 -vtag hvc1 -c:a copy output.mp4

Convert 4k(h.264) to 1080(h.265)

• Downscaling + Change in compression codec

ffmpeg -i input.mp4 -c:v libx265 -vtag hvc1 -vf scale=1920:1080 -crf 20 -c:a copy output.mp4

Compress h.264 with all lang/sub

ffmpeg -i input.mkv -c:v libx264 -crf 23 -c:a copy -c:s copy -map 0:v -map 0:a -map 0:s output.mkv

Options Explained

-i input file name or file path

-c:v libx265 -vtag hvc1` selecting compression. Default is `libx264

-vf scale=1920:1080 specifying output resolution

-c:a copy copy audio as it is without any compression

-preset slow` ask compression algorithm to take more time & look for more areas for compression. Default is `medium`. Other options are `faster`, `fast`, `medium`, `slow`, `slower

-crf 20 Compression quality

-crf 0 high-quality, low compression, large file

-crf 23 default

-crf 51 low-quality, high compression, small file