Function open_sequence 

pub fn open_sequence(
    frames: &[Option<String>],
    rate: FrameRate,
    missing: MissingFrames,
    primaries: Option<LinearPrimaries>,
    resolver: SharedResolver,
) -> Result<Box<dyn VisualSource>, ExtensionError>

Opens an image sequence: frames in play order (None for a gap in the numbering), at rate, their bytes from resolver as they are shown; OpenEXR frames in primaries when given. Only the first frame is read here.

Errors

Why the first frame cannot be read, or the settings are incoherent.