Cannot Burn-In PGS Subtitles

Start by reproducing the conversion with the reported FastFlix subtitle settings and review the logged FFmpeg command, especially the subtitles filter and selected stream. Trace the burn-in path from that command generation point; done means a file with the selected PGS subtitles visibly rendered and conversion completing without the filter error.

FastFlix Version:
v6.2.1

Operating System:
Windows 11 24H2

Describe the bug
Cannot Burn PGS Subs into video

To Reproduce
I've loaded a file into the standard profile, selected Preserve & Burn-In under Subs and left everything else alone and when I hit convert it errors out.

Screenshots
The screen shots are Media Info for the file to see all the streams and the Subtitle settings

Logs (If applicable) In FastFlix you can go to Help > Open Log Directory and sort by latest to find the newest log file to add here.

2026-09-15 20:36:00,644 - Using work dir: C:\Users\User\AppData\Roaming\FastFlix\temp_20260915_ab40b5636b07eada
2026-09-15 20:36:00,645 - command output file set to: C:\Users\User\AppData\Roaming\FastFlix\temp_20260915_ab40b5636b07eada\encoder_output_dbaabe629a15.log
2026-09-15 20:36:00,645 - command error output file set to: C:\Users\User\AppData\Roaming\FastFlix\temp_20260915_ab40b5636b07eada\encoder_error_output_90c6a6ae303d.log
2026-09-15 20:36:00,646 - Running command: ['C:\Users\User\AppData\Roaming\FFmpeg\bin\ffmpeg.exe', '-y', '-i', 'D:\Sources\Working\title_t01.mkv', '-max_muxing_queue_size', '1024', '-filter_complex', "[0:0]subtitles='D\:\\Sources\\Working\\title_t01.mkv':si=3:original_size=1920x1080[v]", '-map', '[v]', '-c:v', 'libx265', '-pix_fmt', 'yuv420p10le', '-x265-params', 'aq-mode=2:repeat-headers=0:strong-intra-smoothing=1:bframes=4:b-adapt=2:frame-threads=0:colorprim=bt709:transfer=bt709:colormatrix=bt709:hdr10_opt=0:hdr10=0:chromaloc=0', '-crf:v', '22', '-preset:v', 'medium', '-map_metadata', '-1', '-map_chapters', '0', '-map', '0:1', '-metadata:s:1', 'title=Stereo', '-metadata:s:1', 'handler=Stereo', '-metadata:s:1', 'language=jpn', '-c:1', 'copy', '-disposition:1', 'default', '-map', '0:2', '-metadata:s:2', 'title=Stereo', '-metadata:s:2', 'handler=Stereo', '-metadata:s:2', 'language=jpn', '-c:2', 'copy', '-disposition:2', '0', '-default_mode', 'infer_no_subs', 'D:\Output\title_t01.mkv']
2026-09-15 20:36:00,658 - Set command priority to Normal
2026-09-15 20:36:00,689 - ffmpeg version n8.0-28-g7cbc26267b-20251027 Copyright (c) 2000-2025 the FFmpeg developers
2026-09-15 20:36:00,700 - built with gcc 15.2.0 (crosstool-NG 1.28.0.1_403899e)
2026-09-15 20:36:00,710 - configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32threads --enable-pthreads --enable-iconv --enable-zlib --enable-libxml2 --enable-libvmaf --enable-fontconfig --enable-libharfbuzz --enable-libfreetype --enable-libfribidi --enable-vulkan --enable-libshaderc --enable-libvorbis --disable-libxcb --disable-xlib --disable-libpulse --enable-opencl --enable-gmp --enable-lzma --enable-amf --enable-libaom --enable-libaribb24 --enable-avisynth --enable-chromaprint --enable-libdav1d --enable-libdavs2 --enable-libdvdread --enable-libdvdnav --disable-libfdk-aac --enable-ffnvcodec --enable-cuda-llvm --enable-frei0r --enable-libgme --enable-libkvazaar --enable-libaribcaption --enable-libass --enable-libbluray --enable-libjxl --enable-libmp3lame --enable-libopus --enable-libplacebo --enable-librist --enable-libssh --enable-libtheora --enable-libvpx --enable-libwebp --enable-libzmq --enable-lv2 --enable-libvpl --enable-openal --enable-liboapv --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopenmpt --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --disable-libdrm --enable-vaapi --enable-libvidstab --enable-libvvenc --enable-whisper --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --enable-libzvbi --extra-cflags=-DLIBTWOLAME_STATIC --extra-cxxflags= --extra-libs=-lgomp --extra-ldflags=-pthread --extra-ldexeflags= --cc=x86_64-w64-mingw32-gcc --cxx=x86_64-w64-mingw32-g++ --ar=x86_64-w64-mingw32-gcc-ar --ranlib=x86_64-w64-mingw32-gcc-ranlib --nm=x86_64-w64-mingw32-gcc-nm --extra-version=20251027
2026-09-15 20:36:00,721 -
2026-09-15 20:36:00,721 - libavutil 60. 8.100 / 60. 8.100
libavcodec 62. 11.100 / 62. 11.100
libavformat 62. 3.100 / 62. 3.100
libavdevice 62. 1.100 / 62. 1.100
libavfilter 11. 4.100 / 11. 4.100
libswscale 9. 1.100 / 9. 1.100
libswresample 6. 1.100 / 6. 1.100
[Parsed_subtitles_0 @ 00000191e49dfc40] libass API version: 0x1704000
[Parsed_subtitles_0 @ 00000191e49dfc40] libass source: commit: 534a5f8299c5ab3c2782856fcb843bfea47b7afc
[Parsed_subtitles_0 @ 00000191e49dfc40] Shaper: FriBidi 1.0.16 (SIMPLE) HarfBuzz-ng 12.1.0 (COMPLEX)
[Parsed_subtitles_0 @ 00000191e49dfc40] Unable to locate subtitle stream in D:\Sources\Working\title_t01.mkv
[AVFilterGraph @ 00000191e49c01c0] Error initializing filters
Error : Operation not permitted

Please make sure to remove any personal information or video names in the screenshots and logs!