I have a LibreOffice Impress slideshow that I wish to turn into a narrated video.
1. export the slideshow as PNG images (if that is partially broken — as at now — at higher resolutions, Export Directly as PDF then use ‘pdftoppm’ (from the poppler-utils package) to do the same).
2. write a small C program (63 lines including comments) to display those images one at a time, writing a config file entry for Imagination (default transition: ‘cross fade’) based on when the image-viewer application (‘display,’ from the GraphicsMagick suite) is closed on each one; run that, read each image aloud, then close each image in turn.
3. run ‘Imagination’ over the config file to produce a silent MP4 video with the correct timings.
4. run ‘Audacity’ to record speech while using ‘SMPlayer’ to display the silent video, then export that recording as a WAV file.
4a. optionally, use ‘TiMIDIty’ to convert a non-copyright-encumbered MIDI tune to WAV, then import that and blend it with the speech (as a quiet background, gently drowning out random sounds and providing a little audio infill between words and sentences).
5. use ‘ffmpeg’ to blend the video and audio together (‘-c:v copy’). perhaps adjust the audio timing with Audacity (then re-export), and repeat if the audio timing is imperfect.