Seminar: Real-Time Record and Playback Application by using Audio Unit

Huizhong Liu
M.Sc. Candidate
Supervisor: Dr. Yuanzhu Chen

Real-Time Record and Playback Application by using Audio Unit

Department of Computer Science
Tuesday, July 31, 2018, 10:00 a.m., Room EN 2022


Audio processing is one of the most important functionalities in mobile applications. In IOS. development, there are several efficient and convenient frameworks for audio recording and playback such as AV Foundation, Audio Toolbox frameworks etc. However, most of them can provide playback function only after the recording process is finished. In many situations, we need the real-time playback of synthesized sounds, low-latency I/O such as VoIP phone service, hearing aids, and voice changer. In this case, we can use audio unit framework to achieve this goal, which is the lowest programming layer in the IOS audio stack and can provide fast, modular audio processing.

Audio data compression has the potential to reduce the transmission bandwidth and storage requirements of audio data. Lossy audio compression is used in a wide range of applications. In this project, we implemented an application which can record and playback the sound simultaneously by using Audio Unit framework. Besides, we encoded raw audio data to MP3 file by using LAME, one of the best open source high-quality MPEG Audio Layer III (MP3) encoder.