Create video with reference images - Veo 3.1

post /v1/ai/reference-to-video/veo-3-1 Generate a video with character or object consistency using reference images. Maintains visual identity across scenes for storytelling and multi-scene projects. Supports 720p, 1080p, and 4K resolutions with native audio generation including dialogue and sound effects. Fixed 8-second duration at 24 FPS.