Feature request: implement VideoLDM-approach #462

First of all thanks for that great library, bringing generative models to the monai framework and also for the nice tutorials!

I was wondering if it would be possible to add the implementation described by Blattmann et al. in their paper "Align your Latents:
High-Resolution Video Synthesis with Latent Diffusion Models" (https://arxiv.org/abs/2304.08818) (see also https://research.nvidia.com/labs/toronto-ai/VideoLDM/), where they, as far as I understand, trained for the sake of efficiency a pre-trained 2D Autoencoder that was fine-tuned on a temporal dimension (for video-generation, which would be the z-dimension in medical images) by adding 3D layers to the decoder.

For GenerativeModels-integration, I was thinking of

• a new dataloader class, that makes a 2D dataset out of 3D images by taking slice from each volume to train the 2D autoencoder
• add 3D-layers to the autoencoder's decoder to patch-wise fine-tune it on 3D-data

Maybe, this approach could also help to generate synthetic medical 3D datasets in a diagnostic resolution.

Looking forward to hear your opinion on this topic.

Best, Lorenz