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AI startup Return Zero transforms phone calls into texts

Startup veterans create an AI speech recognition app that helps users keep track of their conversations

By Aug 10, 2021 (Gmt+09:00)

ReturnZero CEO Lee Cham-sol explains voice recognition service Vito on Aug. 10.
ReturnZero CEO Lee Cham-sol explains voice recognition service Vito on Aug. 10.

South Korea-based startup Return Zero is enhancing the quality of life for people through its voice recognition app, Vito, which provides phone call transcriptions in a text messaging format.

Due to the global pandemic, there is an increased number of people working from home or in a contactless environment which has made phone calls and virtual meetings more frequent, creating more work for people who need to take notes during calls or transcribe their calls afterward.

But Vito helps address such troubles by transcribing the call and sending it to the user almost immediately after the call ends.

"Vito has processed over 2.1 million hours worth of speech," said Lee Cham-sol, the chief executive of Return Zero, in an interview with The Korea Economic Daily on Aug. 10. This is a drastic growth given that the app had processed around 130,000 hours worth of speech just a year ago.

Vito's recognition accuracy for unclean speech data, in this case referring to general phone quality, stands at around 80%. As for clean speech data such as audiobooks, Vito's recognition accuracy is close to 100%.


Founded in 2018, Return Zero is the second startup set up by CEO Lee along with Jung Joo-young, the chief technology officer, and Lee Hyun-jong, the head of development. They met while attending the country's top science and engineering university, Korea Advanced Institute of Science and Technology (KAIST).

In 2011, the three members launched a mobile social commerce service Lotiple Inc., which was acquired by Korea's mobile giant Kakao Corp. less than a year later. Following the acquisition, the founding team members of Return Zero joined Kakao and developed various services during its early days.

Eventually, CEO Lee departed from Kakao and decided to set up another startup to develop speech recognition services because he believed that it was the most tangible and useful artificial intelligence (AI) service in our everyday life.

"Simply put, Return Zero is an AI startup that concentrates on applying the latest research developments into the real world," said CEO Lee.


Return Zero’s forte lies in its advanced speech recognition technology.

"Speech recognition is one of the oldest segments in the AI space, but it has been difficult to come across a service that fully satisfies users due to lack of relevant data," said CEO Lee, adding that Vito is one of the best performing startup in the country in terms of processing natural conversations and speaker diarization.

On Vito, users can receive their call transcriptions in a text messaging format which makes it easier to read. Users can also play the recorded call by tapping the text message alongside utilizing search and edit features.

The startup's ultimate goal is to offer the best level of Korean speech recognition in the world considering that the current level of Korean speech recognition technology isn't as advanced as English or Chinese.

"We want to advance our technology to allow all types of tasks to be processed by speech recognition-based services," said Lee, adding that Vito is a part of that process.

The startup recently raised an additional 16 billion won ($13.9 million) in a Series B funding round from investors including KTB Network, Atinum Investment Co., Hana Ventures and Company K Partners. So far, Return Zero has secured 19.8 billion won in total.

Return Zero plans to use the latest proceeds to boost its research and development, hiring, and global expansion. The startup is also in the works to release an enterprise service given the high demand, according to CEO Lee.

Write to Joo-wan Kim at

Danbee Lee edited this article.

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