The requirement to transmit video data over unreliable wireless networks (with the possibility of packet loss) is
anticipated in the foreseeable future. Significant compression ratio and error resilience are both needed for complex
applications including tele-operated robotics, vehicle-mounted cameras, sensor network, etc. Block-matching based
inter-frame coding techniques, including MPEG-4 and H.264/AVC, do not perform well in these scenarios due to error
propagation between frames. Many wireless applications often use intra-only coding technologies such as Motion-JPEG,
which exhibit better recovery from network data loss at the price of higher data rates. In order to address these research
issues, an intra-only coding scheme of H.264/AVC (iAVC) is proposed. In this approach, each frame is coded
independently as an I-frame. Frame copy is applied to compensate for packet loss. This approach is a good balance
between compression performance and error resilience. It achieves compression performance comparable to Motion-
JPEG2000 (MJ2), with lower complexity. Error resilience similar to Motion-JPEG (MJ) will also be accomplished.
Since the intra-frame prediction with iAVC is strictly confined within the range of a slice, memory usage is also
extremely low. Low computational complexity and memory usage are very crucial to mobile stations and devices in
wireless network.
With the proliferation of digital multimedia content, information hiding techniques have attracted more and more research interests. Information hiding not only hides the content and location of the protected data, but also hides its very existence. High-bitrate information hiding is different from digital watermarking in that it tries to hide relatively large amounts of auxiliary information instead of just one or a few verification bits. This research is mainly concerned with channel capacity and robustness to lossy image/video codec. In the proposed DCT (discrete cosine transformation) domain algorithm, 1 bit is hidden within each 8×8 DCT coefficient block by means of vector quantization. A mathematical model has been proposed to predict the bit error rate (BER) of the algorithm under transformation-based lossy compression. The channel capacity can be increased 4-fold with further performance improvement. Digital video information hiding is a natural extension of digital image information hiding. Experimental results show that the proposed algorithm is very robust to lossy image/video codec. It is also observed that hidden information within different types of frames/slices have different levels of robustness against H.264/AVC compression. The proposed algorithm shall be very useful in practical applications such as side information delivery, captioning, video-in-video, and speech-in-video.
Piezoelectric micromotor, as one kind of the mainly actuator in Micro Electro Mechanical Systems, has been paid a great deal of attention to. This paper offers an idea of measuring the dynamic performance of a piezoelectric micromotor by means of Laser Doppler Avemometry. Based on the idea, the transient response and influence of some factors of an around travelling wave ultra motor are inspected.
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