Take a screenshot with subtitles of every mkv file in the directory, at 10 seconds after the video starts

mkvScreenshot.bat

rem Take a screenshot with subtitles of every mkv file in the directory, 
rem at 10 seconds after the video starts

@echo off
SET count=1
FOR /f "tokens=*" %%G IN ('dir /b') DO (call :subroutine "%%G")
GOTO :eof

:subroutine
 set tmp=%1
 set ext="%tmp:~-5%
 IF %ext%==".mkv" (
   set fn=%tmp:~0,-5%
   echo Take screen shot %fn%.mkv
   ffmpeg -i %1 -map 0:s:0 %fn%.srt
   ffmpeg -ss 00:00:10 -copyts -i %1 -vf subtitles=%fn%.srt" -vframes 1 %fn%.jpg"
 )
 set /a count+=1
 GOTO :eof