Video Error Correction Using Steganography
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ideo Error Correction Using Steganography David L. Robie Center for Signal and Image Processing, Georgia Institute of Technology, Atlanta, GA 30332, USA Email: [email protected]
Russell M. Mersereau Center for Signal and Image Processing, Georgia Institute of Technology, Atlanta, GA 30332, USA Email: [email protected] Received 15 May 2001 and in revised form 14 November 2001 The transmission of any data is always subject to corruption due to errors, but video transmission, because of its real time nature must deal with these errors without retransmission of the corrupted data. The error can be handled using forward error correction in the encoder or error concealment techniques in the decoder. This MPEG-2 compliant codec uses data hiding to transmit error correction information and several error concealment techniques in the decoder. The decoder resynchronizes more quickly with fewer errors than traditional resynchronization techniques. It also allows for perfect recovery of differentially encoded DCT-DC components and motion vectors. This provides for a much higher quality picture in an error-prone environment while creating an almost imperceptible degradation of the picture in an error-free environment. Keywords and phrases: error concealment, error correction, data hiding, steganography, MPEG-2.
1. INTRODUCTION Video transmission requires the use of a compression algorithm in order to decrease the bandwidth to an affordable value, and MPEG-2 is a widely accepted standard [1]. MPEG-2 achieves compression through the elimination of temporal, spatial, and statistical redundancies with the use of motion compensation, block quantization inside a discrete cosine transform (DCT), and Huffman run-length encoding. This compression, while reducing redundancies, creates a bitstream that is much less fault tolerant. For example, single bit errors can cause a loss of synchronization that will be visible over an entire group of pictures (GOP). When considering the transmission of MPEG-2 video, one must be able to deal with the errors and the resulting loss of synchronization. The frailties of MPEG-2 have been addressed by both encoding and decoding schemes. Many encoding schemes use data partitioning to enhance the robustness of the MPEG-2 stream. This can include additional resynchronization points by decreasing the length of slices or decreasing the number of frames in the GOP, but this comes at a cost of increased bit rate. An alternative is to partition the data in time, scale or SNR [2]. In any of the data partitioning modes, the multiple layers of data add resilience and are fully supported by MPEG-2; however, they increase the total bit rate. Other methods include sending additional side information to enhance the recovery of the decoder, re-
organizing the data to improve the resynchronization of the decoder or the use of forward error correction. An example of side information is the transmission of the concealment vectors, provided in the MPEG-2 standard, to recover lost data in I-frames. A system that reorgani
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