Load a TTML, WebVTT, SCC or STL file and scrub through a live preview of how the captions render — positioning, styling and timing, composited over a checkerboard, solid color, or load a video.
Format
SCC channel
CC1/CC2 are multiplexed in the same byte stream via distinct control-code pairs.
SCC frame rate
SCC timecodes are frame-based with no framerate in the file — VTT is time-based and TTML carries its own framerate, so neither needs this.
STL info
Grid size and frame rate are read from the file's own GSI header once loaded.
Background
Click to choose a background video
Aspect
Guides
Grid aspect
Fits the caption grid to this shape, centered within the video frame — for captions authored for a different aspect than the video itself.
Source file
↓Drag & drop a TTML, VTT, SCC or STL file, or click to browse
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This is a QC preview tool — it approximates common TTML/IMSC, WebVTT, SCC and STL rendering conventions but is not a spec-certified renderer. Always verify final output against the target platform's own player.