Reversible data hiding methods based on audio and video synchronization in MP4 container

In this work, two reversible data hiding methods are proposed by exploiting the audio-video synchronization process in the MP4 container. Specifically, audio-video synchronization information is stored as time-to-sample information in the stts box of the MP4 container. In Method 1, the number of sample counts in the stts box is decomposed into multiple integers, where each integer represents the decimal equivalent of the payload (represented in binary) to be hidden. Method 1 completely preserves the audio-video synchronization before and after hiding data into the MP4 container. To suppress bitstream size increment and improve the number of bits that can be hidden, Method 2 is proposed by manipulating both timescale and duration of sample δ to hide data. Basic performance of the proposed methods are verified through experiments on various H.264/AVC and AAC compressed short movie clips downloaded from YouTube. In the worst case scenario, a negligible bitstream size increment of < 0.0447% and absolute synchronization error of < 13 milliseconds were observed when payload of length 1024 bits is embedded into the movie clips.