Free online SUB to SUP converter

A Blu-ray authoring application or player may accept PGS/SUP subtitles but reject a DVD-era SUB file. Converting it creates a Blu-ray-compatible subtitle stream for authoring, playback, or archiving.

What the SUB format is

In video subtitles, .sub identifies more than one format. The two common variants are MicroDVD, a text format with frame-based timestamps, and VobSub, a bitmap format usually distributed as a matching .sub and .idx pair.

MicroDVD files contain subtitle text and numbered entries; the frame rate is needed to interpret their timing correctly. VobSub files contain rendered subtitle images, while the .idx file supplies timing, language, palette, and positioning information. VobSub is common in DVD rips and is used by older media players, subtitle tools, and video-processing applications.

Identify the variant before converting. A text editor can usually open MicroDVD SUB as readable text. A large binary-looking SUB accompanied by an IDX file is normally VobSub.

What the SUP format is

For Blu-ray subtitles, .sup normally means a Presentation Graphic Stream (PGS). PGS stores timed bitmap graphics rather than editable characters, allowing Blu-ray authoring software and compatible players to display fixed fonts, outlines, colors, and positions.

SUP is appropriate when a Blu-ray project requires PGS or when the subtitle must render consistently on a target player. It is less convenient to edit than text subtitles, can be larger, and must be rendered for the project’s video dimensions and Blu-ray subtitle constraints.

Convert VobSub SUB with BDSup2Sub

BDSup2Sub is the practical desktop choice for converting a VobSub pair directly to Blu-ray SUP. It transfers the existing bitmap subtitles, so OCR is not required and the original subtitle wording is not reconstructed as text.

1. Put the matching .sub and .idx files in the same folder. Do not rename one without updating the pair.
2. Open BDSup2Sub and choose File → Open; select the .idx file. The application loads the associated SUB bitmap stream.
3. Set the target video resolution, frame rate, subtitle position, and any required cropping or palette options. Use the resolution of the Blu-ray project, such as 1920×1080 or 1280×720.
4. Review timing, forced-subtitle flags, line placement, and colors in the preview. Correct overlaps or offsets before export.
5. Choose the program’s SUP export or save command, select Blu-ray SUP/PGS when offered, and save the output file.

Because BDSup2Sub converts images to images, it preserves the source artwork more reliably than an OCR workflow. It cannot recover missing characters or improve a low-resolution source.

Convert text-based MicroDVD SUB

Use Subtitle Edit for a text-based SUB. It can interpret the subtitle text, render it with selected styling, and export a Blu-ray SUP/PGS stream.

1. Open Subtitle Edit and choose File → Open, then select the MicroDVD .sub file.
2. Provide the source video or set the correct input frame rate if requested. A wrong frame rate causes timing drift that increases toward the end of the file.
3. Check the first and last entries against the video, then correct reading speed, line breaks, overlaps, forced entries, and spelling.
4. Set the target resolution and subtitle appearance, including font, size, outline, color, and screen position.
5. Use File → Save as or the applicable export command and select Blu-ray SUP, PGS/SUP, or the equivalent Blu-ray subtitle format shown by the installed version.

The conversion rasterizes the text into graphics. Keep the original MicroDVD file because the exported SUP no longer provides the same convenient text-based editing.

Use the 101convert file converter

For a supported upload, the free converter on 101convert.com can create SUP without installing software: upload the SUB file, select SUP as the output, start the conversion, and download the result. A VobSub conversion may also require the associated .idx file; use desktop software when the service cannot accept paired inputs, identify the SUB variant, or control Blu-ray rendering settings.

Quality and compatibility limits

• VobSub-to-SUP conversion is usually a bitmap reformat, not a text conversion. Image defects, palette limitations, low resolution, and incorrect source positioning remain visible.
• MicroDVD-to-SUP conversion depends on the correct frame rate, video dimensions, font settings, and subtitle placement. Review accented characters, line wrapping, timing, and forced subtitles after export.
• A SUP rendered for one frame size may be misplaced or scaled in another project. Match the authoring project’s exact dimensions and verify that the target application expects Blu-ray PGS SUP rather than a proprietary SUP variant.
• Test the exported file in the intended Blu-ray authoring application and, when possible, on the target player. Some authoring tools require additional stream, language, or forced-subtitle metadata.