Subtitles not working on Azure Function

[keke1210]

I have deployed an azure function with ffmpeg.exe. The function adds audio and srt/ass subtitles to a video.
When I test locally this code works (running on azurite). When I deploy The audio is added to the video but the subtitles don't show up. I've tried with SRT and ASS but they both don't work using this code.

What am I doing wrong?

await FFMpegArguments
 .FromFileInput(videoInputPath, true, options =>
 {
     options.WithCustomArgument("-stream_loop -1");
 })
 .AddFileInput(audioPath, true)
 .OutputToFile(videoOutputPath, true, (options) =>
 {
     options.WithDuration(thread.AudioData.TotalAudioDuration);

     options.WithVideoCodec(VideoCodec.LibX264);   // Re-encode video using x264 codec
     options.WithAudioCodec(AudioCodec.Aac);       // Re-encode audio to AAC
     options.WithSpeedPreset(Speed.VeryFast);
     options.UsingShortest(true);

     options.WithVideoFilters((videoOptions) =>
     {
         videoOptions.HardBurnSubtitle(SubtitleHardBurnOptions.Create(subtitlesFile));
     });
 }).ProcessAsynchronously();

Here's the command it creates on Azure function:

-stream_loop -1 -i "C:\local\Temp\videoTempPath.mp4" -i "C:\local\Temp\audioTempPath.mp3" -t 00:00:22.8160000 -c:v libx264 -c:a aac -preset veryfast -shortest -vf "subtitles='C\:\\local\\Temp\\subtitles.srt'" "C:\local\Temp\output.mp4" -y