Data hiding in MP4 video container based on subtitle track

This paper proposes a data hiding method in MP4 container format. Specifically, the synchronization between subtitle and audio-video tracks is exploited to hide data. The time scale is first scaled, and the sample duration pair is modified to hide data. The proposed method is able to hide data reversibly when the payload size is relative small, and it switches to the irreversible mode to offer higher payload. Although synchronization between audio-video and subtitle tracks are manipulated, the delay or ahead in displaying subtitle is imperceptible. The filesize of the processed MP4 file is also completely preserved. Subjective evaluations are carried out to verify the basic performance of the proposed method.