Abstract
Most practical high-resolution text-to-image systems rely on latent diffusion models, where generation is performed in a compact latent space and a decoder maps latents back to pixels. Yet the latent-to-pixel decoder is reconstruction-oriented, optimized to invert the encoder rather than synthesize more details, and becomes increasingly costly at megapixel scale. This drawback calls for a more expressive and efficient decoding paradigm. Motivated by recent progress in scalable pixel-space diffusion, we introduce PiD, a Pixel diffusion Decoder that reformulates latent decoding as conditional pixel diffusion, unifying decoding and upsampling into one generative module. By denoising directly in high-resolution pixel space, PiD synthesizes 4× and even 8× upscaled images with low latency. For latent conditioning, a lightweight sigma-aware adapter injects noise-corrupted latents into the pixel diffusion backbone, enabling PiD to decode partially denoised latents and terminate the latent diffusion process early. To further improve efficiency, we distill the model using DMD2, reducing inference to just 4 steps. PiD applies to both conventional VAE latents and semantic latents (e.g., SigLIP, DINOv2) used in recent RAE-based models. PiD decodes latents of 512×512 images into 2048×2048 pixels in under 1 second with 13 GB peak memory on a consumer RTX 5090, and as fast as 210 ms on a GB200 GPU, about 6× faster than cascaded diffusion-based super-resolution pipelines with better visual fidelity.
Results
From Latent to Pixels
Select a latent space and move the step slider to compare PiD decoding quality at different early-termination points.
Drag the white divider on each image to reveal the VAE/RAE decode vs. PiD decode.
4K Decode
Direct latent→4K decoding with PiD.
Click any image to launch a side-by-side comparison against the VAE decoder.
Baseline Comparison
Hover over any image to activate the synchronized zoom lens across all six views.
Quantitative Results (Decoding + Upsampling, 512² → 2048²)
End-to-End Decoding Latency (ms) ↓
PiD is up to 5.9× faster than SeedVR2 (211.2 ms vs 1237.5 ms)
Gemini-3-Flash Judge Rating (%) ↑
% of evaluations where judges prefer PiD over each baseline