Recently very deep transformers start showing outperformed performance to traditional bi-directional long short-term memory networks by a large margin. However, to put it into production usage, inference computation cost and latency are still serious concerns in real scenarios. In this paper, we study a novel non-autoregressive transformers structure for speech recognition, which is originally introduced in machine translation. During training input tokens fed to the decoder are randomly replaced by a special mask token. The network is required to predict those mask tokens by taking both context and input speech into consideration. During inference, we start from all mask tokens and the network gradually predicts all tokens based on partial results. We show this framework can support different decoding strategies, including traditional left-to-right. A new decoding strategy is proposed as an example, which starts from the easiest predictions to difficult ones. Some preliminary results on Aishell and CSJ benchmarks show the possibility to train such a non-autoregressive network for ASR. Especially in Aishell, the proposed method outperformed Kaldi nnet3 and chain model setup and is quite closed to the performance of the start-of-the-art end-to-end model.

本研究提出了两种不自回归变换器结构以解决自动语音识别中的推理计算成本问题，在训练期间，输入的标记被特殊的掩码标记随机替换，网络需要考虑未被掩盖的上下文和语音输入以预测与那些掩码标记相对应的标记。结果表明，该模型能够支持不同的解码策略，特别是在 Aishell 上，该方法的性能超过了 Kaldi ASR 系统，与最先进的自回归变换器的性能相当，而且速度提高了 7 倍。

听写填空：用于语音识别的非自回归变压器