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reduce file size of mp4 using ffmpeg

ffmpeg -i input.mp4 -vcodec libx264 -crf 24 output.mp4

ffmpeg reduce video size

$ ffmpeg -i "[inputName.mp4]" -vcodec [libx265]  -crf [28] "[outputName.mp4]"
# vcodec: libx265 for HVEC or libx264 for H.264
# crf: ranges form 0-51, (Value > less quality & size), (Value < Higher quality & size, size can get higher than the original size)
# To ouput Matroska/Mkv ad: -f matroska

ffmpeg reduce video size

ffmpeg -i input.mp4 -fs 100M output.mp4

ffmpeg -i input.mp4 -vcodec libx264 -crf 24 output.mp4