How to tonemap PGS subtitles for HDR contents (4K Blu-ray)

Standard Blu-ray PGS subtitles are very bright on HDR content (HDR10, HDR10+, HLG, Dolby Vision). This guide shows how to tonemap them to a darker, less bright gray.

Requirements

1. BDSup2Sub
2. Java Runtime
3. Subtitle Tonemap Tool

Instructions

1. Install Java Runtime.

2. Create a new folder. Place the downloaded BDSup2Sub512.jar and subtitle_tonemap.exe files inside it.

   

3. Demux the PGS subtitle track(s) from your source (BDMV or REMUX). Use eac3to, MKVToolNix, or a tool like MKVCleaver as shown.

   
   Extract the subtitle file(s) to the folder containing subtitle_tonemap.exe.

4. Open a command prompt (cmd) in the folder containing the tool and subtitle file.

   

5. Run the command:
   subtitle_tonemap.exe "path/to/subtitles" -o tonemapped --percentage 60

   
   Replace "path/to/subtitles" with the actual filename. The --percentage 60 argument sets the white level to 60% (recommended). Adjust this value as needed. The -o tonemapped argument specifies the output folder name.

6. After processing, find the tonemapped subtitle file in the new tonemapped folder.

   

7. Mux the new subtitle file into your REMUX using MKVToolNix.

Comparison (on a SDR screen)

Original

Tonemapped (60%)

The difference is more significant on an HDR monitor or TV.

Credits

Old owners - Unknown (not a username)
New / Current owner - Clara

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