How to Add Font size in subtitles in ffmpeg video filter
Solution 1
There are two methods to use subtitles: hardsubs and softsubs.
Hardsubs
The subtitles
video filter can be used to hardsub, or burn-in, the subtitles. This requires re-encoding and the subtitles become part of the video itself.
force_style
option
To customize the subtitles you can use the force_style
option in the subtitles
filter. Example using subtitles file subs.srt
and making font size of 24 with red font color.
ffmpeg -i video.mp4 -vf "subtitles=subs.srt:force_style='Fontsize=24,PrimaryColour=&H0000ff&'" -c:a copy output.mp4
-
force_style
uses the SubStation Alpha (ASS) style fields. -
PrimaryColour
is in hexadecimal in Blue Green Red order. Note that this is the opposite order of HTML color codes. Color codes must always start with&H
and end with&
.
Aegisub
Alternatively, you can use Aegisub to create and stylize your subtitles. Save as SubStation Alpha (ASS) format as it can support font size, font color, shadows, outlines, scaling, angle, etc.
Softsubs
These are additional streams within the file. The player simply renders them upon playback. More flexible than hardsubbing because:
- You do not need to re-encode the video.
- You can have multiple subtitles (various languages) and switch between them.
- You can toggle them on/off during playback.
- They can be resized with any player worth using.
Of course sometimes hardsubs are needed if the device or player is unable to utilize softsubs.
To mux subtitles into a video file using stream copy mode:
ffmpeg -i input.mkv -i subtitles.ass -codec copy -map 0 -map 1 output.mkv
Nothing is re-encoded, so the whole process will be quick and the quality and formats will be preserved.
Using SubStation Alpha (ASS) subtitles will allow you to format the subtitles however you like. These can be created/converted with Aegisub.
Also see
subtitles
video filter documentation- How to burn subtitles into the video
- How to convert subtitle from SRT to ASS format
Solution 2
From the documentation you can use a srt subtitle file and change the size of the font by putting ASS style format KEY=VALUE
pairs separated by ,
. So,
ffmpeg -i input.mp4 -vf subtitles=sub.srt:force_style='FontName=DejaVu Serif,FontSize=24' -vcodec libx264 -acodec copy -q:v 0 -q:a 0 output.mp4
will put the subtitles with DejaVu font and size 24 while keeps the quality of the video. I've tried myself and it worked.
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khizar ansari
Updated on January 15, 2022Comments
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khizar ansari over 2 years
I'm using this command to crop,scale, and then add subtitles as overlay
ffmpeg -i input.avi -vf "[in]crop=in_w:in_h-20:0:0 [crop]; [crop]scale=320:240 [scale];[scale]subtitles=srt.srt" -aspect 16:9 -vcodec libx264 -crf 23 oq.mp4
how can we set font size/color of subtitle ?
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Roland Seuhs about 9 yearsThe question how to change the font size was not answered, please provide syntactically correct example
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llogan about 9 years@RolandSeuhs The answer states that it is not possible with SRT (as far as I know). As for ASS, the actual ASS file dictates the font size; as you can see in the example file.
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LEM over 8 yearsThis works, but be sure that you have created the FC_CONFIG_DIR, FONTCONFIG_FILE and FONTCONFIG_PATH environment variables and the file fonts.conf exists, otherwise it won't work.
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Gabriel Devillers over 3 yearsThis command worked thanks, but only if I enclosed the parameter to
-vf
with double quotes. -
Tony M over 3 yearsThis hardcode sub command works, but like @GabrielDevillers says, only with double quotes around -vf parameter.