Hybrid Audio-video Record System For PBL Lecture

Problem Based Learning(PBL)teaching method has been widely applied and studied in schools at home and abroad.Different from the traditional classroom based on teacher teaching,students’ speech and discussion in PBL classroom are their main behaviors.Teachers need to record students’ speech behaviors and contents so as to form an evaluation of students’ overall participation performance.The circular sitting layout used in PBL classroom brings challenges to the deployment of classic classroom recording schemes such as video surveillance.Aiming at the measurement needs of students’ speech behavior in the loop sitting scene in PBL classroom,this thesis proposes a scheme to deploy acquisition equipment in the center of PBL classroom.In this scheme,the mixed measurement is a hybrid of audio-video,in which the sound field positioning technology is used as the main discriminant method,and the video positioning technology corrects the audio measurement results,which makes up the deficiency of pure sound field measurement under special circumstances.In this thesis,six microphone arrays are used for sound field positioning.The basic application range of sound field measurement is obtained through pre-measurement,and the main direction of the speaker is obtained through array positioning.In terms of video positioning,this thesis adopts a 360-degree fisheye camera,which can obtain panoramic images of multiple students sitting in the circle.After image processing,the speaker with active lips can be identified.The fusion of the two measurement methods can effectively overcome the special conditions such as proximity of speaker seats and movement of speaker.The practical deployment test of PBL classroom in Tongji Medical College of Huazhong University of Science and Technology shows that the recording system developed in this thesis can effectively identify the speech behavior and orientation of students in PBL classroom,and can record the speech behavior in PBL classroom completely.This thesis solves the practical problem of automatic recording of PBL teaching activities by means of audio-video mixed measurement,which has a certain reference role for the research and development of future intelligent application of classroom for free discussion.