  AISHELL-1 is by far the largest open-source speech corpus available for
Mandarin speech recognition research. It was released with a baseline system
containing solid training and testing pipelines for Mandarin ASR. In AISHELL-2,
1000 hours of clean read-speech data from iOS is published, which is free for
academic usage. On top of AISHELL-2 corpus, an improved recipe is developed and
released, containing key components for industrial applications, such as
Chinese word segmentation, flexible vocabulary expension and phone set
transformation etc. Pipelines support various state-of-the-art techniques, such
as time-delayed neural networks and Lattic-Free MMI objective funciton. In
addition, we also release dev and test data from other channels(Android and
Mic). For research community, we hope that AISHELL-2 corpus can be a solid
resource for topics like transfer learning and robust ASR. For industry, we
hope AISHELL-2 recipe can be a helpful reference for building meaningful
industrial systems and products.
