Pages that turn themselves, in time with the reading.
A read-along is a stack of pages and a recording of someone reading them. This is the one workflow ClapperBoard can time for you: it listens to the narration, reads the pages, matches one against the other, and sets every page's duration to fit.
Words in the audio. The match is made between what is spoken and what is printed, so the recording has to be speech. Music has nothing to match against — for a score, see sheet music, where the timing is placed by hand.
Readable text on the pages. A PDF with a real text layer is ideal; ClapperBoard uses it directly. Scans and photographs are read with text recognition instead, which works well on clean pages and less well on ornate type, heavy layout or poor contrast.
Both lanes filled. Tools › Sync to Audio stays unavailable until the project holds at least one image and one audio item.
Choose Tools › Sync to Audio. What follows is one sheet that moves through several stages.
First it asks which audio to handle, given as a range — From and To — and tells you how many items there are and how many are not yet transcribed.
Transcripts are kept, so a second run does not redo work already done. On a long book split into many audio files, that means you can transcribe a few at a time rather than committing to the whole thing in one sitting.
Alignment is the slow part on a long book, and it shows a progress bar rather than a spinner because it can take a while.
Alignment quality can be changed here, and again in the review. Default compares everything. The faster settings skip common words, or compact long pages, or both — each trades a little accuracy for speed. It is worth starting with Default and only reaching for the others if a book is large enough to be tedious.
Nothing changes until you agree to it. The review lists every page with:
| Column | Meaning |
|---|---|
| Before / After | The page's current duration, and what the sync proposes. |
| Confidence | How well that page's words matched the narration. |
| Skip | Leaves this page's timing alone. |
Low confidence is a signal to look, not a failure in itself — an illustration-only page has few words to match, and will score low while being perfectly well placed by its neighbours.
Skip is for pages that should not be retimed at all. ClapperBoard suggests it for pages that look like a table of contents or an index: a page of chapter titles and page numbers has plenty of words, none of which are read aloud, so it would otherwise attract matches it should not have. Reset Skips clears your choices and starts again.
The review also lists the gaps it found — real silences in the narration, which are usually where one page ends and the next begins.
Rather than cutting a page at the exact word the alignment matched, ClapperBoard centres each break in the largest genuine silence nearby, so a page does not turn in the middle of a spoken phrase. The break offset lets you shift that.
If the pages run past the end of the recording, the review says so and offers to add silence to the audio lane, so both end together instead of the video continuing over nothing.
Apply Changes commits the durations. Everything is one undoable step, so a sync you dislike can be undone in one go.
The sync may add spacer items to keep the two lanes aligned. Reorder mode removes them, because freely reordering items would invalidate their positions — ClapperBoard asks before doing it. Nothing is lost: running the sync again regenerates them.
If the book has a table of contents, ClapperBoard reads it during the sync and turns it into a chapters button in the toolbar, listing the entries with their printed page numbers. It is a quick way to jump to a chapter while checking the result.
The button appears only when a table of contents was found, and re-populates each time you apply a sync.
Whole pages are a coarse unit — a page of a novel can hold a minute of narration. Smart Text Crop cuts each page into separate items, by paragraph, by a set number of blocks, or every few lines, and each becomes its own item on the timeline.
Do that before syncing. The sync then times those smaller pieces, and the video follows the reading a paragraph — or a line — at a time.
A single long recording can be cut where you want it: put the playhead where the split belongs and press S — Split Audio at Playhead. Useful for dividing a book into chapters so they can be transcribed a few at a time.
Audio items can also be faded, and their levels shaped — see transitions.