Projects can be configured with caption limits. CaptionHub is continually checking to see if your captions obey these limits, and it will warn immediately you they don't. The realtime QC button will turn red, and the appropriate caption will be highlighted in red, either on the timeline, or the spreadsheet view – depending on what CaptionHub thinks is wrong.
Clicking on the realtime QC button will tell you, in plain language, what needs to be fixed. Each issue has a hyperlink that will take you to the appropriate caption on the spreadsheet view.
The constraints that CaptionHub checks for are:
Character length per line
The maximum number of characters in a single line of a caption. (Captions may have one or two lines, depending on the "Number of lines" limit. If you exceed the allowed amount, the character count for that line will turn red.
Number of lines
The number of lines in a single caption. If this is exceeded, the entire caption box will turn red. Careful: an extra carriage return (new line) at the end of the caption will add an extra line, which might cause errors.
The minimum or maximum time a caption can appear on screen for. The original caption set has been set up with all captions at least the correct length. Should you alter the timings, any caption that lasts less than the minimum duration, or longer than the maximum duration, will turn red in the timeline.
CaptionHub can be configured to warn the user if captions are too close together, usually according to a broadcast standard. A minimum frame gap can be configured, and CaptionHub will enforce this where possible, and warn the user if not.