Caption Conversion Guides
Convert Caption & Subtitle Files
Caption conversion is lossy in ways the file never tells you about. These guides cover what survives each conversion, what breaks, and what you have to supply that the source file does not contain.
What makes caption conversion go wrong?
Three things, almost always: a frame rate that was relabelled instead of conformed, a character set the target format cannot represent, and positioning or styling silently dropped because the destination has nowhere to put it. None of the three produces an error message.
Converting to a broadcast deliverable
Getting subtitles into a format playout will accept. The recurring problems are frame rate conforms and the CEA-608 character set.
| Conversion | Typical situation | The hard part |
|---|---|---|
| PAC to SCC | Subtitling house to North American broadcast | Code page identification, and Latin script only |
| EBU-STL to SCC | European material for a US delivery | A real 25 to 29.97 fps conform |
| MCC to SCC | Downgrading a 708 master to a 608 sidecar | Choosing the right caption service |
| CAP to SCC | Legacy archive migration | Identifying which .cap format you have |
| IMSC to SCC | Streaming master back to broadcast | Image-profile files cannot convert at all |
| SCC to EBU-STL | North American material for a European delivery | Deriving out times and filling the STL header |
| PAC to EBU-STL | Subtitling house to European playout | Code page mapping and header metadata |
| SCC to MCC | Adding 708 services or changing frame rate | Deciding whether 708 is worth generating |
Converting for streaming and the web
Moving broadcast or legacy material onto a platform. These conversions generally gain capability rather than losing it, and fail at the validator instead.
| Conversion | Typical situation | The hard part |
|---|---|---|
| SCC to IMSC | Catalogue title going to a streaming platform | Deriving end times, and platform profile validation |
| EBU-STL to IMSC | European broadcast to OTT | Nothing is lost. Passing the platform validator |
| SAMI to WebVTT | Windows Media era archive to a modern player | No end times, and one file per language |
| Cavena 890 to SRT | Making a Nordic broadcast file readable | Character table, and the frame rate you still need |
Looking for what a format carries rather than how to convert it? See the caption and subtitle format reference.
Every conversion in one project
Closed Caption Creator converts between 30+ caption and subtitle formats, conforms frame rates against picture, and QC-checks the result before delivery.