Reversible data hiding in Standard MIDI Files by adjusting delta time values

In this paper, an effective method of hiding information in Standard MIDI Files (SMF) is presented. The method simultaneously shifts the binary representations of both the division value and non-zero delta time values in a MIDI file left in order to hide information, and embeds secret information in the bits of the non-zero delta time values produced by the left shifting. The number of left shift bits is in accordance with both the tolerance of beat-changing and the size of the secret information to be embedded. Experimental results show that the proposed method is not only able to embed secret information in Standard MIDI Files without influencing their playing quality, but is also able to recover the original MIDI files without distortion after the hidden data have been extracted.