How to change ffmpeg default font size?

Linux and Unix-Like Ubuntu
1

Hello,

I have a problem with Greek subtitle font size when I map a subtitle file into a video in ffmpeg .

I ran below code:

ffmpeg -i video.mp4 -sub_charenc CP1253 -i video_sub.srt -c:v copy -c:a copy \ 
-c:s mov_text -metadata:s:s:0 language=gr mapped_video.mp4

When I play it in VLC, it gives very small subtitle size.

Then I tried to increase subtitle fontsize but no luck.

ffmpeg -strict -2 -i video.mp4 -sub_charenc CP1253 -vf subtitles=video_sub.srt:force_style='Fontsize=30' \ 
-qscale:v 3 -c:v copy -c:a copy -c:s mov_text -metadata:s:s:0 language=gr mapped_video.mp4

Also tried this one but failed again:

ffmpeg -strict -2 -i video.mp4 -sub_charenc CP1253 -vf "subtitles=video_sub.srt:force_style='Fontsize=30'" \
-qscale:v 3 -c:v copy -c:a copy -c:s mov_text -metadata:s:s:0 language=gr mapped_video.mp4

As default fontsize in ffmpeg is 16, this time I increased fontsize from 16 to 30 in vf_drawtext.c file, then I reconfigured ffmpeg and replaced new ffmpeg binary file but nothing changed.

PS: I tested below code as -vf is invalid when -c:v copy is selected..

ffmpeg -strict -2 -i video.mp4 -sub_charenc CP1253 -vf subtitles=video_sub.srt:force_style='Fontsize=30' \ 
-qscale:v 3 -c:v libx264 -c:a copy -c:s mov_text -metadata:s:s:0 language=gr mapped_video.mp4

Could you please explain how I may do this?

Thanks
Boris

2

Please post your system details.

Thanks.

3

Hello Neo,
Here you are:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.5 LTS
Release:        14.04
Codename:       trusty

Linux bv0791 3.13.0-119-generic #166-Ubuntu SMP Wed May 3 12:18:55 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Kind regards
Boris