Some Tibetan characters aren't rendered correctly with ffmpeg.

[张一环]

 I'm trying to use ffmpeg drawtext filter to render Tibetan text to videos. But some characters aren't rendered correctly.

what I expected render output:



Actual render output:






As you can see the first character was distorted.


( I'm a newbee to a mailing list, don't know if images are supported, so here's 
a stackoverflow link if images above aren't displayed:
https://stackoverflow.com/questions/62458321/ffmpeg-drawtext-support-for-tibetan-fonts
 )


Here's my ffmpeg command line:


ffmpeg -i input.mp4 -filter_complex 
"drawtext=fontsize=80:fontcolor=black:fontfile=himalaya.ttf:shadowx=1:shadowy=1:text='སྤྱི་སྟེགས':x=0:y=0"
 -c:v libx264 -b:v 400k -c:a copy output.mp4

The font himalaya.ttf (Microsoft Himalaya) is the default built-in font for 
Tibetan on Windows. (See 
https://docs.microsoft.com/en-us/typography/font-list/microsoft-himalaya )


I tried many other Tibetan fonts, and many ffmpeg versions, problem exists 
anyway.


All of those fonts are rendered correctly in other places such as a web browser.



I wonder is this a bug or I missed some configuration? and who should I 
contact for support, you or ffmpeg people?


Thank you!