Veo 3.1 reference-to-video update Veo 3.1 Preview models now support the following features

## Feature Feature **Veo 3.1 reference-to-video update** Veo 3.1 Preview models now support the following features: * 9:16 aspect ratio for reference-to-video. * Upsampling for videos generated at 1080p and 4k resolutions. For more information, see the following: * [Generate Veo videos from reference images](https://cloud.google.com/vertex-ai/generative-ai/docs/video/use-reference-images-to-guide-video-generation) * [Veo on Vertex AI video generation API](https://cloud.google.com/vertex-ai/generative-ai/docs/model-reference/veo-video-generation)