[FFmpeg-user] mp4 files size problem

Cley Faye cleyfaye at gmail.com
Thu Sep 7 17:09:09 EEST 2017

2017-09-07 15:57 GMT+02:00 Daniel <5960761 at gmail.com>:

> Hello Everyone,
> I have tried to convert some videos to mp4 format what has surprised me
> was the size of the videos, After the conversion some videos were 2,3,4
> times bigger then the original wmv files. Here is the command i used to
> convert :  /usr/local/bin/ffmpeg -i video500.wmv -c:a libfdk_aac -c:v
> nvenc_h264  video500.mp4 ; After this command the mp4 file is 630MB  and
> the wmv file is 150MB (you can find attached the ffprobe to bothe files).
> If you can suggest any way on how to keep the quality and make the mp4
> files smaller please let me know .
> ps: On some mp4 videos the bitrate has doubled have no idea why ?

​If you don't supply your own settings, ffmpeg (and/or the underlying
codec) will assume some default values, not necessarily in compliance with
the input. In your case, you probably want (at least) to set the bitrate.
Also, I think that hardware encoder tend to produce bigger file for same
quality (and worse quality for same size), but this might not be accurate

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