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---
license: mit
pipeline_tag: audio-to-audio
---

# SimVQ: Addressing Representation Collapse in Vector Quantized Models with One Linear Layer

[![arXiv](https://img.shields.io/badge/Arxiv-2411.02038-AD1C18.svg?logo=arXiv)](https://arxiv.org/abs/2411.02038)

This repository contains the SimVQ model, presented in the paper [Addressing Representation Collapse in Vector Quantized Models with One Linear Layer](https://huggingface.co/papers/2411.02038).

SimVQ tackles the problem of representation collapse in Vector Quantization (VQ) models by reparameterizing code vectors through a learnable linear transformation layer. This method optimizes the *entire linear space* of the codebook, leading to improved codebook utilization and robust performance across various modalities, including image and audio tasks.

Code is available at [https://github.com/youngsheen/SimVQ](https://github.com/youngsheen/SimVQ).

## Abstract

Vector Quantization (VQ) is essential for discretizing continuous representations in unsupervised learning but suffers from representation collapse, causing low codebook utilization and limiting scalability. Existing solutions often rely on complex optimizations or reduce latent dimensionality, which compromises model capacity and fails to fully solve the problem. We identify the root cause as disjoint codebook optimization, where only a few code vectors are updated via gradient descent. To fix this, we propose **SimVQ**, which reparameterizes code vectors through a learnable linear transformation layer over a latent basis, optimizing the *entire linear space* rather than nearest *individual code vectors*. Although the multiplication of two linear matrices is equivalent to applying a single linear layer, this simple approach effectively prevents collapse. Extensive experiments on image and audio tasks demonstrate that SimVQ improves codebook usage, is easy to implement, and generalizes well across modalities and architectures. The code is available at [https://github.com/youngsheen/SimVQ](https://github.com/youngsheen/SimVQ).

## Algorithm for SimVQ

You can find the core code here [https://github.com/youngsheen/SimVQ/blob/main/taming/modules/vqvae/quantize.py#L28-L33](https://github.com/youngsheen/SimVQ/blob/main/taming/modules/vqvae/quantize.py#L28-L33)

<p align="center">
<img src="https://huggingface.co/zyx123/SimVQ/resolve/main/assets/Algorithm.png" alt="SimVQ Algorithm">
</p>

**Note:** Optimizing both the codebook C and the linear layer W can work as well.

## Quantitative Comparison

**Table 1.** Reconstruction performance of different tokenizers on $128 \times 128$ ImageNet 50k validation set.
| Method | Codebook Size | Codebook Utilization | rFID | LPIPS | PSNR | SSIM | Checkpoint |
|:------:|:-------------:|:----:|:----:|:---------------------:|:----:|:----:|:----:|
|VQGAN | 65,536 |  1.4% | 3.74 |  0.17 | 22.20 | 70.6 | -|
|VQGAN | 65,536 |  4.5% | 3.23 |  0.15 | 22.89 | 72.3 | -|
|VQGAN-FC | 65,536 | 100.0% | 2.63 | 0.13 | 23.79 | 77.5 | - |
|FSQ | 64,000 | 100.0% | 2.80 | 0.13| 23.63 | 75.8 | - |
|LFQ | 65,536 | 100.0% | 2.88 | 0.13| 23.60 | 77.2 | - |
|VQGAN-LC | 65,536 | 100.0% | 2.40 | 0.13 | 23.98 | 77.3 | - |
|SimVQ (ours) | 1024 | 100.0% | 3.67 | 0.16 | 22.34 | 70.8 | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_log/simvq_1k) |
|SimVQ (ours) | 8192 | 100.0% | 2.98 | 0.14 | 23.23 | 74.7 | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_log/simvq_8k) |
|SimVQ (ours) | 65,536 | 100.0% | **2.24** | **0.12** | **24.15** | **78.4** | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_log/simvq_65k) |
|SimVQ (ours) | 262,144 | 100.0% | **1.99** | **0.11** | **24.68** | **80.3** | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_log/simvq_262k) |

**Table 2.** Reconstruction performance of different tokenizers on LibriTTS test clean/other set.

| Method | Bandwidth | Codebook Utilization | UTMOS | PESQ | STOI | V/UV F1 | Checkpoint |
|:------:|:-------------:|:----:|:----:|:---------------------:|:----:|:----:|:----:|
|Encodec | 3.0kbps | -/-% | 2.31/2.09 | 2.05/2.05 | 0.90/0.88 | 0.92/0.89 | - |
|Vocos | 3.0kbps | -/-% | 3.53/3.06 | 2.40/2.19 | 0.92/0.90 | 0.94/0.91 | - |
|SpeechTokenizer | 3.0kbps | -/-% | 3.56/3.02 | 1.93/1.74 | 0.88/0.84 | 0.93/0.89 | - |
|WavTokenizer | 0.9kbps | 100/100% | 3.74/3.43 | 2.01/2.26 | 0.89/0.89 | 0.92/0.92 | - |
|WavTokenizer | 1.05kbps | 27/-% | 4.00/- | 2.36/- | 0.81/- | 0.94/- | - |
|SimVQ (ours) | 0.9kbps | 100.0/100.0% | 4.00/3.51 | 2.33/2.08 | 0.91/0.88 | 0.94/0.91 | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_audio_log/simvq_4k) |
|SimVQ (ours) | 0.975kbps | 99.4/99.4% | 4.03/3.52 | 2.42/2.15 | 0.92/0.88 | 0.94/0.92 | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_audio_log/simvq_8k) |
|SimVQ (ours) | 1.2kbps | 99.4/99.0% | 4.03/3.52 | 2.54/2.26 | 0.93/0.90 | 0.94/0.92 | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_audio_log/simvq_65k) |
|SimVQ (ours) | 1.35kbps | 95.6/94.7% | 4.03/3.53 | 2.61/2.31 | 0.93/0.90 | 0.95/0.93 | [huggingface](https://huggingface.co/zyx123/SimVQ/tree/main/vq_audio_log/simvq_262k) |

## Implementations

### Installation

- **Dependencies**: `pip install -r requirements.txt`
- **Extra dependencies for audio evaluation**: `pip install -r requirements_audio.txt`
- **Datasets**
```
imagenet
└── train/
    β”œβ”€β”€ n01440764
        β”œβ”€β”€ n01440764_10026.JPEG
        β”œβ”€β”€ n01440764_10027.JPEG
        β”œβ”€β”€ ...
    β”œβ”€β”€ n01443537
    β”œβ”€β”€ ...
└── val/
    β”œβ”€β”€ ...
```

```
LibriTTS
└── train-clean-100/
    β”œβ”€β”€ 103/
        β”œβ”€β”€ 1241/
            β”œβ”€β”€ 103_1241_000000_000001.wav
            β”œβ”€β”€ ...
    β”œβ”€β”€ 1034
    β”œβ”€β”€ ...
└── train-clean-360/
    β”œβ”€β”€ ...
└── train-other-500/
    β”œβ”€β”€ ...
└── dev-other/
    β”œβ”€β”€ ...
└── dev-clean/
    β”œβ”€β”€ ...
└── test-other/
    β”œβ”€β”€ ...
└── test-clean/
    β”œβ”€β”€ ...
```

### Training Scripts
* Image Tokenizer Training
```bash
XDG_CACHE_HOME="dataset/ILSVRC2012" python main.py fit --config configs/imagenet_simvq_128_B.yaml
```

* Audio Tokenizer Training

You can get manifest .txt with `generate_manifest.py`

```bash
DATA_ROOT="/data3/yongxinzhu/libritts/LibriTTS" CUDA_VISIBLE_DEVICES=4,5,6,7 python main.py fit --config configs/libritts_24khz.yaml
```

**Note:** Some users have reported encountering NaN issues when training SimVQ on audio data. This appears to be a random occurrence, but we have found that using learning rate warmup can help mitigate the problem.

### Evaluation Scripts
* Image Tokenizer Evaluation
```bash
XDG_CACHE_HOME="dataset/ILSVRC2012" python evaluation.py --config_file vq_log/simvq_262k/size128/config.yaml --ckpt_path vq_log/simvq_262k/epoch=49-step=250250.ckpt
```

* Audio Tokenizer Evaluation
```bash
DATA_ROOT="dataset/libritts" python evaluation_speech.py --config_file vq_audio_log/simvq_262k/1second/config.yaml --ckpt_path vq_audio_log/simvq_262k/epoch=49-step=138600.ckpt
```

## Reconstruction Visualization

**Figure 2.** Visualization of the Open-MAGVIT2 tokenizer trained at $128 \times 128$ resolution (`imagenet_simvq_128_Base` version). (a) indicates the original images while (b) specifies the reconstruction images.
<p align="center">
    <img src="https://huggingface.co/zyx123/SimVQ/resolve/main/assets/case_image.png" alt="Image Reconstruction Visualization">
</p>

**Figure 3.** Visualization of the Open-MAGVIT2 tokenizer trained at LibriTTS (`libritts_24khz` version). (a) indicates the original images while (b) specifies the reconstruction images.
<p align="center">
    <img src="https://huggingface.co/zyx123/SimVQ/resolve/main/assets/case_audio.png" alt="Audio Reconstruction Visualization">
</p>

## Acknowledgement
The codebase of SimVQ is adapted from [Open-MAGVIT2](https://github.com/TencentARC/Open-MAGVIT2) and [WavTokenizer](https://github.com/jishengpeng/WavTokenizer). Thanks for their wonderful work.