How to Convert SRT to STL for DVD Authoring | AllSubConverter
If you are authoring a DVD with Apple DVD Studio Pro or a Spruce-based authoring tool, that software expects subtitles in STL (Spruce Subtitle) format, not the SRT files you probably already have. To get your subtitles onto a DVD project, you need to convert SRT to STL. This guide covers what STL is, how it differs from SRT, and how the conversion works.
What Is the STL Format?
STL is a text-based subtitle format used in DVD authoring. Each subtitle is a comma-delimited line containing a start timecode, an end timecode, and the caption text, with the pipe character (|) marking line breaks. The file usually begins with a // Spruce Subtitle File comment header.
Timing in STL is frame-based SMPTE timecode, either 25fps for PAL DVDs or 29.97fps for NTSC. This is different from SRT, which uses millisecond timestamps with no concept of frames.
STL is the bridge between modern SRT subtitles and legacy DVD authoring tools.
How SRT and STL Differ
The biggest difference is timing. SRT timestamps (HH:MM:SS,mmm) are millisecond-based, while STL uses frame-based timecode (HH:MM:SS:FF). Converting to STL means rounding each cue to the nearest frame. Line breaks also change: SRT newlines become | pipe characters in STL.
STL has no styling beyond basic italic and position control codes, so most SRT content transfers cleanly. The text and the cue timing are what matter for DVD subtitles.
How to Convert SRT to STL
Upload your SRT file to our free SRT to STL converter. The tool converts the millisecond timing to frame-based timecode, translates line breaks to pipe characters, and writes a valid STL file ready for import into DVD Studio Pro.
Choose the correct frame rate for your project, 25fps for PAL or 29.97fps for NTSC, so the timecodes align with your video.
Frequently Asked Questions
Is STL the same as EBU STL?
No. This text-based Spruce STL is for DVD authoring and is unrelated to the binary EBU STL broadcast format. The two are completely different despite sharing an extension.
Does converting to STL lose timing precision?
Slightly. STL timing is frame-based, so millisecond values round to the nearest frame (40ms at 25fps, about 33ms at 29.97fps). The cue boundaries stay accurate to one frame.
Can I convert STL back to SRT?
Yes. The STL to SRT converter reads Spruce STL files and reconstructs standard SRT with millisecond timing.