There are two types of conversion modes available. One for text-based subtitles and another one for picture-based subtitles. For text-based subtitles we currently support SRT, ASS and VTT. We do plan to support more formats in the future.

For subpictures, supported formats are DVD/Bluray (SUP) and VobSub (SUB/IDX) subtitles. For Vobsub conversion, there must be a pair of SUB and IDX files uploaded. The SUB file contains the cues, and the IDX index file describes when to display the cues. To be considered a pair, the paired SUB and IDX files must have the same filename, e.g. subtitle_file_1.sub and subtitle_file_1.idx.

Do not confuse the VobSub SUB files with the text-based SUB files that also use the same file extension. One way to tell whether a SUB file is a text-based file or not is simply by opening it in a text editor. If you can read the cues (with timestamps) then it's a text-based SUB file. The VobSub SUB file would just basically be displayed as garbled machine code.

Subpicture files contained in a compressed zip or rar file must be extracted out first. The background job will automatically compress the files before uploading. Text-based subtitles won't be uploaded to the server because the conversion is done in the browser. You can enable the picture-based subtitle conversion by switching on the Subpicture Mode.