The Research On The Methods Of Embedding Telemetry Data Into MPEG4 Stream In Micro Air Vehicle

When the Micro Air Vehicle communicates with the ground, it transmits not only the real-time video to the ground, but also its own telemetry data. In order to avoid transmitting the two different kinds of data in two separate channels, the compounding transmitting solution which mixes the telemetry data and the video data into one bitstream is proposed. This solution can save channels, reduce the system energy consumption and ensure the security of the telemetry data. Because of the channel bandwith limitation, the video data must be compressed through MPEG4 coding before transmission. Usually the quantity of telemetry data is smaller than the quantity of the video data, so the telemetry data is embedded into MEPG4 stream to realize compounding the telemetry data and the video data.First of all, the method of embedding encrypted telemetry data through self-defined start code is proposed. A new video start code is defined to embed telemetry data into MPEG4 stream, and the telemetry data is encrypted by DES encryption algorithm, Logistic map encryption algorithm, Arnold transform encryption algorithm separately to ensure the security of telemetry data before embedding.Secondly, the method of embedding telemetry data in quantized DCT coefficients is studied by referring to video watermark based on DCT coefficients. Quantized DCT coefficients include DC coefficients and AC coefficients. The telemetry data is embedded in the least significant bit of quantized DCT coefficient to realize compounding the telemetry data and MPEG4 stream.Finally, the methods of embedding telemetry data in Motion Vectors and VLC domain are studied. The telemetry data is embedded in the least significant bit of Motion Vector which has higher amplitude in the method of embedding telemetry data in Motion Vectors. The method of embedding telemetry data in VLC domain has two steps. First, a new code table is build through searching the suitable codeword in the VLC table, and then the telemetry data is embedded into MPEG4 stream through exchanging codeword in the new code table.The above methods are analyzed and compared by experiments, the result show that the method of embedding telemetry data through self-defined start code and the method of embedding telemetry data in high frequency AC coefficients can satisfy the requirement of the project in aspects of complexity, Peak Signal Noise Ratio and quantity of embedded data.