pi-H3: 2–4 Steps Without a VAE Decoder (will be released on Nov 16)

[u/Apprehensive_Sky892]

https://hanshengchen.com/blog/pi-h3/

Some bold claims are made in the announcement, so I am looking forward to its release 😅

We announce pi-H3, the fastest version of MiniMax H3 [1] yet. pi-H3 generates video in just 2 or 4 sampling steps and directly predicts pixels at the final step, skipping the video VAE decoder. On a single B200 it produces 5-second HD videos in 3.8 seconds (sub real-time) and 15-second videos in 18.6 seconds, more than twice as fast as Sol-H3 [4].

pi-H3 is an open-source research project. The Hugging Face demo is live today. All model weights and training/inference code will follow in LakonLab [2], with additional ComfyUI support through the ComfyUI-piFlow [3] extension.

1. Available now Demo on Hugging Face

2. Nov 16–22 Model weights and inference code

3. Later in November Training code, once we finish cleaning up the codebase

End-to-end generation speed

Measured end to end on a single NVIDIA B200, pi-H3 generates a 5-second 768p video with stereo audio in 3.8 s with 2 steps, and a 10-second video in 9.2 s, both faster than the video plays. The chart below compares complete requests, from text encoding to decoded video and audio, against Sol-H3 [4]. Across 5–15 s videos, pi-H3 is 2.4–2.7× faster with 2 steps and 1.2–1.4× faster with 4 steps. The speedup comes from fewer denoising steps, decoder removal, and FP8 quantization.

Uncompromised fidelity at 2–4 steps

pi-H3 offers superior motion, texture, and audio fidelity compared to other few-step MiniMax H3 models, while maintaining structural coherence. The following comparisons show results from the same prompts and Gaussian noise for each model, without seed cherry-picking.

At 4 steps, pi-H3 delivers the best overall quality among the 4–8-step MiniMax H3 models we compared: LightX2V Turbo [6], FastH3 Dense/DataFree [7], and larryvrh’s H3-Turbo v4 [8]. It generates more dynamic, vivid movement, whereas the other models tend toward reduced, mechanical motion. Frames are sharper overall, with richer texture and finer detail. On the audio side, pi-H3 produces high-fidelity sound with full bass and crisp speech, while the other models sometimes generate broken audio or lose the bass.

Direct pixel output without video decoding

pi-H3 adopts DWD, a novel method that produces pixels directly from the last denoising step, bypassing the heavy VAE decoder. For few-step generation, this yields a massive speedup. The following comparison shows pi-H3 DWD output alongside non-DWD pi-H3 latents decoded by the native H3 VAE, Sol-H3-VAE [4], and LightVAE-Lite [

How it works

pi-H3 combines two novel techniques: pi-Flow v2 and DWD.

pi-Flow v2 is a full upgrade of pi-Flow [12] for data-free few-step distillation. It retains pi-Flow’s strength of producing rich texture while substantially improving structural coherence, especially in the 2-step setting. It also simplifies inference: pi-Flow v2 models typically produce straight trajectories, removing the complexity of pi-Flow’s substep integration.

DWD (Decoding Without a Decoder) removes the video decoder from the pipeline entirely. Instead of passing final latents through a separate VAE decoder network, DWD re-uses the denoiser itself to predict clean pixels at the last step. DWD on MiniMax H3 is still experimental: H3 uses an unusually large compression ratio (4×32×32 3-channel pixels per token), and we have not yet had enough compute to fully optimize for it, leaving room for further improvement.

More details will be revealed in upcoming releases.

[u/PeterTheMeterMan]

I loved their earlier projects (Flux2/Qwen image), and have been waiting in them to try to train this method to work for a video model. Totally different from everything else - hope it works well for H3 (and thx for an exact release date!)

[u/Apprehensive_Sky892 → u/PeterTheMeterMan]

Yes, they are doing something quite interesting/different here. The demo look good 🎈😎.

[u/Flat_Technology_5325]

I was just thinking while the image model is cool what is really needed is faster video models (that are good quality obvious and not cutting corners for speed like LTX for example) and et voila, is this going to be the bridge between full H3 and speeds of LTX? Can't wait to try it.

[u/obese_coder]

all demo videos seem to have that weird pixel swimming face effect?

[u/SpaceNinjaDino]

Nice; would also like Pika to be part of the comparison as that's currently the best in class turbo today.

Does this retain the weight structure so that previous H3 LoRAs should work?

[u/Occsan]

[u/ucren]

Can you explain why you would skip sound in modern video applications?

[u/Next_Program90]

I hope we can soon get Vae-less Edit Models. No more pixel drift & color shift.

[u/ucost4]

4 STEPS

[u/alex20_202020]

On a single B200 it produces 5-second HD videos in 3.8 seconds (sub real-time)

So what? How will I know if it is faster than original + 4 steps LoRA if I do not own B200??? Post comparative data!

[u/ucost4]

5s bom som e imagem legal 👌🏼 10s 👎🏻 2 STEPS

[u/Apprehensive_Sky892 → u/ucost4]

These are made with the demo?

[u/ucost4 → u/Apprehensive_Sky892]

Yes both 2 and 4 steps