AZ_BATCH_APP_PACKAGE not working

Hi All,

Trying to run this command -
string taskCommandLine = string.Format(@"cmd /c %AZ_BATCH_APP_PACKAGE_ffmpeg#4.3%\ffmpeg-4.3-win64-static\bin\ffmpeg.exe -i {0} {1}", inputMediaFile, outputMediaFile);

But the inside batch task stderr.txt file I'm getting "System cannot find the path specified" every time. But when I tried a different command to test "cmd /c echo test > sample.txt" then it worked and uploaded the file into the destination blob. Please help me!!!