NetEase Yidun AI Lab paper selected for ICASSP 2023! Black technology makes speech recognition more 'listening' and more accurate

2023-06-07 17:42:41 Author: Li Wenwen

Every science fiction fan longs for the future to be able to launch an interstellar spaceship and conquer the stars and sea with just a few words, just like talking to an old friend; or to have Iron Man’s artificial intelligence butler Jarvis, who can make a Come up with a set of nano battle armor. In fact, this picture is not far away from us - it is as close to us as Siri in the iPhone. Behind it is Automatic Speech Recognition technology. This key technology can convert speech into text or commands that can be recognized by computers, achieving a convenient, efficient, and intelligent human-computer interaction experience.

With the development of AI technologies such as deep learning, speech recognition technology has made tremendous progress - not only the recognition accuracy has been greatly improved, but also it can better handle issues such as accents, noise and background sounds. However, as technology continues to be applied in life and business, it will still encounter some bottlenecks. After all, there are too many practical factors to consider from theoretical research to practical applications, from papers to products. How to make speech recognition better assist content review? How can the recognition action itself be like the human brain, based on the understanding of the context, and give more accurate answers at a lower cost? Yidun AI Lab, a subsidiary of NetEase Intelligence, has given a new approach.

Yidun comes out with black technology again, and smart companies are heading towards the world!

Recently, the global speech and acoustics conference ICASSP 2023 announced the list of selected papers, and the paper submitted by Yidun AI Lab, a subsidiary of NetEase Intelligence Enterprise, was successfully accepted. This year is the 48th ICASSP conference, and it is also the first offline conference after the epidemic. Although the conference officials have not announced the final number of papers accepted, the number of papers submitted has increased by 50% compared to previous years, reaching an astonishing 6,000 .

Faced with such fierce competition, the NetEase Zhiqi Yidun AILab team relied on a paper on speech recognition "Improving CTC-based ASRModels with Gated Interplayer Collaboration (CTC-based model improvement to achieve a stronger model)" Structure)》 stood out and successfully got tickets to attend the offline conference in Rhodes Island, Greece.

“GIC”, helps speech recognition go further

Speech recognition is essentially the conversion of speech sequences into text sequences. To complete such a conversion, generally use three types of models, CTC, Attention-based and RNN-Transducer, they are completing Different paths were used during the task:

CTC: Based on the neural network model, the model parameters are updated through backpropagation during the training process to minimize the loss function. This algorithm introduces "whitespace characters" to represent meaningless characters or space symbols. CTC is suitable for processing data with large differences in input and output lengths, such as mapping acoustic features to text in speech recognition;

Attention-based: The attention mechanism is also based on the neural network model and uses a technology called "attention" to weight the input. At each time step, the model calculates a distributed weight vector based on the current state and all inputs, and applies it to all inputs to produce a weighted average as the output. This method can make the model better focus on some information related to the current prediction;

RNN-Transducer: Transcriptor, this algorithm combines the encoder-decoder framework and autoregressive modeling ideas, and considers the interaction between the source language sentences and the generated partial target language sentences when generating the target sequence. Unlike the other two methods, RNN-Transducer does not clearly distinguish between the encoder and decoder stages, and converts directly from source language to target language, so it can simultaneously consider between source language sentences and generated partial target language sentences. interaction.

Compared with the latter two, although CTC has natural non-autoregressive decoding properties, the decoding speed is relatively faster, but it still has performance disadvantages:

1. The CTC algorithm sets the conditional independence assumption, that is, CTC assumes that the outputs of each time step are independent. This is not reasonable for speech recognition tasks. If the pronunciation "ji rou" is pronounced, the predicted text content should be different in different contexts. If the above sentence is "I like to eat", the probability of "chicken" should be higher. Similarly, if the sentence above is "He has arms", the probability of "muscle" should be higher. If you pass CTC training, it is easy to output funny text like "I like to eat muscles" while ignoring the above;

2. From a modeling perspective, the Attention-based model and the RNN-Transducer model predict the output of the current time step based on the input and the output of the previous time step, while the CTC model only uses the input to predict the current output. During the modeling process of the CTC model, text information is only passed back to the network as a supervision signal, and does not serve as an input to the network to explicitly promote the prediction of the model.

We hope to solve the above two disadvantages as much as possible while retaining the CTC decoding efficiency. Therefore, we want to start from the CTC model itself and design a lightweight module to introduce text information to the CTC-based model, so that the model can integrate acoustic and text information, learn the interaction between text sequence context, and alleviate Conditional independence assumption of CTC algorithm. But in the process, we encountered two problems: How to inject text information into the CTC model (Encoder CTC structure)? How to adaptively fuse text features and acoustic features?

In order to achieve the above goals, We designed the Gated Interlayer Collaboration (abbreviated as GIC) mechanism. The GIC module mainly includes an embedding layer and a gate unit. Among them, the embedding layer is used to generate text information for each audio input frame, and the gating unit is used to adaptively fuse text information and acoustic information.

Specifically, our method is based on the multi-task learning (Multi-taskLearning) framework, using the output of the middle layer of the encoder module (Encoder) to calculate the auxiliary CTC loss. The objective function of the entire network is the CTC loss of the last layer and the middle layer. Weighted sum of layer-assisted CTC losses. GIC uses the prediction of the middle layer of the network, that is, the probability distribution of the Softmax output, as the soft label of each frame, and the sum of the dot product embedding layer matrices as the text representation of each frame. Finally, the generated text representation and acoustic representation are adaptively fused through a gate control unit and become a new feature input to the next layer. The new features at this time combine text features and acoustic features, allowing the next-level Encoder module to learn acoustic sequence context information and text sequence context information. The framework of the entire model is shown in the figure below:

Experiments on the Conformer and Transformer models show:

1. GIC Supports scene recognition in both Chinese and English, and has achieved significant performance improvements in accuracy;

2. The performance of the GIC model exceeds the Attention-based and RNN-transducer models of the same parameter scale, and has the advantage of non-autoregressive decoding, brings several times the decoding speed improvement;

3. Compared with the original CTC model, GIC has a relative performance improvement of far more than 10% in multiple open source data sets.

Conformer Conclusion under the model

Transformer Conclusion under the model

GIC brings great improvements to the performance of CTC models. Compared with the original CTC model, the GIC module brings approximately 2M additional parameters. Among them, the linear layer used to calculate the auxiliary CTC loss of the middle layer is shared with the last layer and does not bring additional parameters. Multiple middle layers share the embedding layer, bringing 256*5000 parameters which is approximately equal to 1.3M. In addition, the amount of additional parameters required for multiple control gate units is 256*256*2*k, totaling about 0.6M.

Leading technology creates advanced business

The GIC in the paper has been applied in the content review business of NetEase Yidun.

As a one-stop digital content risk control brand under NetEase Intelligence, Yidun has long been focused on technology research and development and innovation in digital content security risk control and anti-spam information. Among them, for digital content that uses sound as a carrier, Yidun provides a variety of audio content audit engines, including various types of audio content such as songs, radio, TV programs, live broadcasts, etc., to promptly detect and filter content that contains sensitive, illegal, and vulgar content. Advertising content voice, thereby reducing the social impact of bad content and creating a good network environment.

For audio with specific semantic content, Yidun uses speech recognition technology to transcribe the speech content in the audio file into text content, and then uses the detection module to analyze and process the text, thereby realizing automated review and filtering of the audio content. Therefore, the accuracy of speech recognition is closely related to the efficiency and accuracy of audio content review, and will directly affect the safety and stability of customers' business operations.

The application of GIC in content review in the paper has achieved significant improvement. In the actual application process, there are two hyperparameters that need to be debugged, namely the multi-task learning coefficient lambda and the number of intermediate layers k. In the 18-layer encoder structure, we found that k=5 and lambda=0.5 have better experimental results. We then start with this setting and fine-tune it to determine the optimal hyperparameters.

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Hero behind the scenes: NetEase Zhiqi Yidun AI Lab

This is not the first time that the Yidun AI Lab team has received such an honor.

As a technical team under NetEase Intelligent Enterprise that has always been at the forefront of artificial intelligence research, Yidun AI Lab is committed to building comprehensive, rigorous, safe and trustworthy AI technical capabilities around refinement, lightweighting, and agility, and continuously improving Digital content risk control service level. Prior to this, the team had won multiple AI algorithm competition championships and important awards:

The First China Artificial Intelligence Competition in 2019 The most advanced A-level certificate in the flag recognition track

The Second China Artificial Intelligence Competition in 2020 The most advanced A-level certificate in the video deep forgery detection track

The 3rd China Artificial Intelligence Competition in 2021 The two most advanced A-level certificates for video deep forgery detection and audio deep forgery detection tracks

2021 "Innovation Star" and "Innovative Figure" of China Artificial Intelligence Industry Development Alliance

2021 The 16th National Human-Computer Speech Communication Academic Conference (NCMMSC2021) "Long and Short Video Multilingual Multimodal Recognition Competition" - Chinese Long and Short Video Live Voice Keyword (VKW) Double Track Champion

Won the first prize of the Science and Technology Progress Award issued by the Zhejiang Provincial Government in 2021

2022 ICPR Multimodal Subtitle Recognition Competition (MSR Competition, the first multi-modal subtitle recognition competition in China) Track Three "Multimodal Subtitle Recognition System that Integrate Vision and Audio" Champion

The future is here, and the time for AI’s iPhone has arrived. Yidun has successfully entered the academic hall of phonetics today, and in the future, technology will bring achievements and progress to all aspects of business, and Yidun will always be by your side.

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