ffmpeg-使用默认字幕将mkv转换为mp4

Question

What is best way to convert mkv to mp4, with default subtitle (that mkv have), and keep same quality of video / audio ?

Currently I'm using this command

ffmpeg -y -i filename.mkv -vf subtitles='filename.mkv' -disposition:s default+forced -c:v libx264 -c:a libmp3lame -crf 27 -preset ultrafast filename.mp4

But the command still not perfect, the mkv have better quality than mp4 generated. Any advise?

Thanks

Answer 1

your preset is lowest possible quality, and crf could be lower, 18 is more or less lossless, this will make the transcoding slower. of course So suggest -crf 18 and -preset slow

If you aren't bothered about which codecs you use you could just copy everything into the mp4 container, which would be megaquick