DreamVAE

A distilled decoder for the ACE-Step 1.5 Oobleck VAE. Drop-in replacement: same [B, 64, T] latent input, same [B, 2, 1920*T] stereo output at 48 kHz. 51.7M parameters (61% of the teacher), 0.24 dB SNR degradation vs. the teacher across 20 diverse music tracks, and 37.2 ms to decode 60 seconds of audio on an RTX 5090 TensorRT FP16 engine (8.66x faster than the teacher in PyTorch, 1.45x faster than the teacher's own TRT engine).

Usage

import json
import torch
from huggingface_hub import hf_hub_download
from safetensors.torch import load_file

repo = "daydreamlive/DreamVAE"
weights = hf_hub_download(repo, "model.safetensors")
config  = hf_hub_download(repo, "config.json")
mod_py  = hf_hub_download(repo, "modeling.py")

import sys, os
sys.path.insert(0, os.path.dirname(mod_py))
from modeling import FastOobleckDecoder

cfg = json.load(open(config))
model = FastOobleckDecoder(
    channels=cfg["channels"],
    input_channels=cfg["input_channels"],
    audio_channels=cfg["audio_channels"],
    upsampling_ratios=cfg["upsampling_ratios"],
    channel_multiples=cfg["channel_multiples"],
).eval().to("cuda")
model.load_state_dict(load_file(weights))

# latents: [B, 64, T]  ->  audio: [B, 2, 1920 * T]
with torch.no_grad():
    audio = model(latents)

Pair with the stock ACE-Step encoder; only the decoder is distilled.

ONNX export is at onnx/model.onnx. Build a TRT engine with scripts/export_trt.py.

Results

Quality (20 diverse FMA tracks, 10 s clips):

vs. original audio	SNR (dB)	STFT dist	Mel dist
Teacher OobleckDecoder	5.0 (std 2.5)	0.698	0.733
DreamVAE	4.7 (std 2.4)	0.695	0.742
Degradation	0.24 dB	better	+0.008

The VAE's own reconstruction error (~5 dB SNR) dominates; DreamVAE's additional error is well under a quarter of that. STFT distance is marginally better for the student; mel distance is 1.1% worse. Informal listening finds the difference inaudible.

Speed (RTX 5090, 60 s stereo audio at 48 kHz, TensorRT FP16):

Backend	Time (60 s)	vs. teacher PyTorch
Teacher PyTorch	321.9 ms	1.00x
Teacher TRT FP16	54.0 ms	5.97x
DreamVAE PyTorch	241.1 ms	1.34x
DreamVAE TRT FP16	37.2 ms	8.66x

Distillation alone is modest (1.45x over the teacher's own TRT engine). The compelling number is the composition with TRT: what a deployment sees moving from stock PyTorch VAE to DreamVAE on TRT is 8.66x.

Architecture

	Teacher	DreamVAE
Parameters	84.4M	51.7M (61%)
Channel multiples	[1, 2, 4, 8, 16]	[1, 2, 4, 8, 8]
Residuals/block	3 (dil 1, 3, 9)	2 (dil 1, 3)
Upsampling ratios	[10, 6, 4, 4, 2]	[10, 6, 4, 4, 2]
Activation	Snake1d	Snake1d
Hop length	1920	1920

Trained for 650K steps on 8,000 FMA Small tracks (two-phase: 500K reconstruction + 150K adversarial). Released checkpoint is step 635K, selected as the HF-energy-match peak from a six-point trajectory over the adversarial phase.

Files

.
├── README.md
├── config.json            architecture + training hyperparameters
├── model.safetensors      FP32 weights (207 MB, 51.7M params)
├── modeling.py            self-contained FastOobleckDecoder class
├── onnx/model.onnx        ONNX export
└── scripts/               training, eval, speed bench, TRT export/verify

Limitations

• Signal-level metrics only (no MUSHRA / PESQ / preference tests).
• Evaluated on VAE round-trip, not end-to-end through the full text-to-DiT-to-VAE pipeline. FAD on generated samples is future work.
• One point on the quality-speed frontier ([1,2,4,8,8], 2 residual units). Width variants not evaluated.
• Trained in FP32. INT8 / FP8 quantization would likely stack another 1.5-2x on top of FP16 and is not explored here.

Citation

Technical note (methodology, training recipe with source-paper attribution, adversarial-phase trajectory, and negative results on encoder distillation) is forthcoming on arXiv. Citation block will be added here on release.

License

Apache 2.0, matching the upstream ACE-Step 1.5 license.