SRT to CAP Converter

The SRT to CAP Converter takes the SubRip captions pasted into the SRT Content box and rewrites them in Cheetah CAP style, where each caption is a start and end timecode pair in HH:MM:SS:FF form followed by the caption text. The frame field is calculated from the value you enter in Frame rate (fps), and the finished file downloads with the .cap extension.

Cheetah CAP belongs to the world of caption encoders and legacy authoring stations that never spoke SubRip. Broadcasters, post houses handling library titles, closed-captioning vendors and anyone feeding an older hardware encoder still get asked for it, usually at short notice and usually when the only source available is the SRT the transcription team produced. Rather than re-timing the whole programme in specialist software, a srt to cap converter lets you reformat what you already have.

The interesting work is the timebase change. SubRip measures time in milliseconds; CAP counts frames, so the converter splits each timestamp into hours, minutes and seconds and turns the leftover milliseconds into a frame number using your chosen rate. At 25 fps one frame is 40 ms, so half a second is frame 12; at 30 fps the same half second is frame 15. Enter the wrong rate and every cue is subtly misplaced, with the error growing across the programme - which is why the Frame rate (fps) field must match the master rather than whatever proxy you previewed on. Cue text is carried across as written, so any line breaks you set for reading speed stay where the subtitler put them.

All of this happens in your browser. No caption file is uploaded, and conversion is effectively instantaneous even for a feature-length title.

• Timecode pairs per cue: output follows the Cheetah convention of a start and end timecode followed by the caption text, so files drop into legacy authoring workflows without reshaping.
• Free-form frame rate: Frame rate (fps) accepts any numeric value, so 23.976 film transfers, 25 fps PAL masters and 29.97 NTSC deliveries are all handled from the same tool.
• Accurate frame maths: the sub-second remainder of every SubRip timestamp is converted to frames at your chosen rate instead of being rounded to whole seconds, keeping cues on the right picture.
• Text passed through unchanged: whatever you paste into SRT Content is what appears under each timecode pair, including the line breaks you chose for on-screen layout.
• Tolerant parsing: mixed line endings, gaps in cue numbering and stray whitespace in the source SRT are absorbed rather than throwing an error.
• Immediate export: copy the result to the clipboard or download it as a .cap file, with no sign-up or per-file limit.
• Fully local: the convert srt to cap online process runs as JavaScript in the page, so nothing about your programme is transmitted.

1. Paste your complete SubRip file into the SRT Content box, or press Load sample to inspect the CAP layout with example data first.
2. Establish the frame rate of the video the captions will be encoded against and type it into Frame rate (fps), such as 25, 29.97 or 23.976.
3. Press Run to convert; the output panel shows each cue as a timecode pair followed by its text.
4. Compare the first cue's start timecode with the same moment in your video to confirm the offset and frame rate are right.
5. Check a cue near the end of the programme too, because frame-rate mistakes accumulate and are clearest at the tail.
6. Click Copy to move the text into another application, or Download to save a .cap file.
7. Load the .cap into your caption encoder or authoring station and keep the original SRT as the editable master for future revisions.

Example 1 - straightforward cue at 25 fps. One frame is 40 ms, so the fractional part of each timestamp maps cleanly.

Input (SRT):
1
00:00:01,000 --> 00:00:04,000
Welcome to the harbour tour.

Output (CAP):
00:00:01:00 00:00:04:00
Welcome to the harbour tour.

Example 2 - a sub-second boundary. A cue running 00:01:12,480 --> 00:01:15,960 converts at 25 fps to 00:01:12:12 00:01:15:24, because 480 ms is twelve frames and 960 ms is twenty-four. Set Frame rate (fps) to 30 instead and the same cue becomes 00:01:12:14 00:01:15:28. Same milliseconds, different frame counts - a reminder that the rate is part of the timing, not a cosmetic setting.

• Answers legacy requests fast: a client asking for Cheetah CAP can be served from your existing SubRip master within minutes instead of days.
• Keeps captions on the right frame: proper frame arithmetic avoids the half-second slips that make captions appear to lead or trail the speaker.
• Avoids QC failures: delivering at the master's true frame rate prevents the accumulating drift that reviewers flag at the end of long programmes.
• No specialist licence needed: freelance subtitlers can produce a broadcast-shaped file without buying into an authoring suite for a single job.
• Protects unreleased material: local conversion means embargoed dialogue is never uploaded to a third-party service.
• Reversible workflow: since your SRT stays untouched, revisions are made once in the master and re-exported rather than patched in two formats.