论文标题
神经图像压缩的多样本训练
Multi-Sample Training for Neural Image Compression
论文作者
论文摘要
本文考虑了有损神经图像压缩（NIC）的问题。当前的最新方法（SOTA）方法采用近似量化噪声的均匀后方，单样本估计量近似于证据下限（ELBO）的梯度。在本文中，我们建议用多个样本重要性加权自动编码器（IWAE）目标训练NIC，该目标比Elbo更紧，并随着样本量的增加而收敛至对数的可能性。首先，我们确定NIC的均匀后验具有特殊的特性，这会影响IWAE目标的路径方向和得分函数估计器的方差和偏差。此外，从梯度差异的角度来看，我们提供了关于NIC中通常采用的技巧的见解。基于这些分析，我们进一步提出了多个样本NIC（MS-NIC），这是NIC的IWAE靶标。实验结果表明，它改善了SOTA NIC方法。我们的MS-NIC是插件，可以轻松扩展到其他神经压缩任务。
This paper considers the problem of lossy neural image compression (NIC). Current state-of-the-art (sota) methods adopt uniform posterior to approximate quantization noise, and single-sample pathwise estimator to approximate the gradient of evidence lower bound (ELBO). In this paper, we propose to train NIC with multiple-sample importance weighted autoencoder (IWAE) target, which is tighter than ELBO and converges to log likelihood as sample size increases. First, we identify that the uniform posterior of NIC has special properties, which affect the variance and bias of pathwise and score function estimators of the IWAE target. Moreover, we provide insights on a commonly adopted trick in NIC from gradient variance perspective. Based on those analysis, we further propose multiple-sample NIC (MS-NIC), an enhanced IWAE target for NIC. Experimental results demonstrate that it improves sota NIC methods. Our MS-NIC is plug-and-play, and can be easily extended to other neural compression tasks.
