Very Low Bit-Rate Video Coding by Combining H.264/AVC Standard and 2-D Discrete Wavelet Transform

In this paper, we propose a new method for very low bit-rate video coding that combines H.264/AVC standard and two-dimensional discrete wavelet transform. In this method, first a two dimensional wavelet transform is applied on each video frame independently to extract the low frequency components for each frame and then the low frequency parts of all frames are coded using H.264/AVC codec. On the other hand, the high frequency parts of the video frames are coded by Run Length Coding algorithm, after applying a threshold to neglect the low value coefficients. Experiments show that our proposed method can achieve better rate-distortion performance at very low bit-rate applications below 16 kbits/s compared to applying H.264/AVC standard directly to all frames. Applications of our proposed video coding technique include video telephony, video-conferencing, transmitting or receiving video over half-rate traffic channels of GSM networks.

Compression of ECG Signals Based on DWT and Exploiting the Correlation between ECG Signal Samples

This paper presents a hybrid technique for the compression of ECG signals based on DWT and exploiting the correlation between signal samples. It incorporates Discrete Wavelet Transform (DWT), Differential Pulse Code Modulation (DPCM), and run-length coding techniques for the compression of different parts of the signal;where lossless compression is adopted in clinically relevant parts and lossy compression is used in those parts that are not clinically relevant. The proposed compression algorithm begins by segmenting the ECG signal into its main components (P-waves, QRS-complexes, T-waves, U-waves and the isoelectric waves). The resulting waves are grouped into Region of Interest (RoI) and Non Region of Interest (NonRoI) parts. Consequently, lossless and lossy compression schemes are applied to the RoI and NonRoI parts respectively. Ideally we would like to compress the signal losslessly, but in many applications this is not an option. Thus, given a fixed bit budget, it makes sense to spend more bits to represent those parts of the signal that belong to a specific RoI and, thus, reconstruct them with higher fidelity, while allowing other parts to suffer larger distortion. For this purpose, the correlation between the successive samples of the RoI part is utilized by adopting DPCM approach. However the NonRoI part is compressed using DWT, thresholding and coding techniques. The wavelet transformation is used for concentrating the signal energy into a small number of transform coefficients. Compression is then achieved by selecting a subset of the most relevant coefficients which afterwards are efficiently coded. Illustrative examples are given to demonstrate thresholding based on energy packing efficiency strategy, coding of DWT coefficients and data packetizing. The performance of the proposed algorithm is tested in terms of the compression ratio and the PRD distortion metrics for the compression of 10 seconds of data extracted from records 100 and 117 of MIT-BIH database. The obtained results revealed that the proposed technique possesses higher compression ratios and lower PRD compared to the other wavelet transformation techniques. The principal advantages of the proposed approach are: 1) the deployment of different compression schemes to compress different ECG parts to reduce the correlation between consecutive signal samples;and 2) getting high compression ratios with acceptable reconstruction signal quality compared to the recently published results.

似图形图像序列压缩编码方案的研究

针对远程炒股、远程教学和远程协同工作中的计算机屏幕共享问题 ,提出了一种对似图形图像序列进行无损压缩的编码方案。首先将似图形图像转化成索引图像 ,然后对索引图像序列进行帧间行程编码和自适应预测Huffman编码 ,最后再对码流进行LZ77编码。实验表明 ,该方案能够有效地压缩似图形图像序列 ,与一般的无损图像编码方案相比 ,明显地提高了图像的压缩效率 ,压缩比可达到 80∶1以上。

基于三态信号的改进游程编码压缩方法

为提高集成电路测试效率,提出一种结合三态信号的改进游程编码压缩方法。先对原始测试集进行部分输入精简处理并填充测试集的无关位,再对经过预处理的测试集根据游程长度进行变长分段处理找出最优段长。按照游程长度的出现频率对最优段长下的参考位设置编码表进行编码压缩,使用三态信号编码标志位并将编码压缩后的测试集存入自动测试设备(ATE),最终通过设计解压电路对ATE中存储的压缩数据进行无损解压。实验结果表明,在硬件开销未明显增加的情况下,该方法的测试数据平均压缩率达到74.39%,优于同类压缩方法。

一种雷达视频信号压缩编码的算法及实现

脉压技术使视频回波变窄,对雷达图像压缩编码提出了更高的要求.在对雷达图像特点进行较深入的分析后,提出了一种新的雷达视频信号压缩编码算法,完成了电路设计及仿真,并分析了该方法的优点及压缩性能.

雷达视频信号压缩编码的研究

现代新体制雷达普遍采用脉压技术使视频回波变窄,因而对雷达图像压缩编码提出了更高的要求。在对雷达图像进行比较深入的分析后.提出了一种新的雷达视频信号压缩编码算法,进行了电路设计及仿真,并分析了该方法的优点。给出了压缩性能。

一种用于版权保护的压缩域视频水印算法

提出一种应用于版权保护的压缩域视频水印算法。结合mpeg-2视频压缩过程,通过在特定位置插入不同游程的方法,实现游程编码过程的水印嵌入,在接收端可以直接从码流中提取水印,也可在游程解码过程中提取水印。实验结果表明,该算法计算复杂度低,实时性与现有视频处理设备兼容性好,且对视频质量影响小,具有良好的码率保持特性和抗再压缩能力。

基于稀疏分解和复合熵编码的电能质量扰动数据高效压缩算法

对于电能质量扰动信号压缩问题,压缩比和重构误差是一对互相矛盾的指标。传统的压缩算法难以同时满足高压缩比和低重构误差的要求。为了同时提高压缩比和减小重构误差,该文提出了一种基于稀疏分解、哈夫曼编码和行程编码的混合压缩算法。首先,使用基于联合字典的稀疏分解算法,将电能质量扰动信号中的暂态分量和稳态分量进行分离;其次,对暂态分量使用小波分析、哈夫曼编码、行程编码算法进行编码压缩,对稳态分量,即基波和谐波分量,则保留其大于设定阈值的部分,进而完成对信号的压缩;最后,仿真信号和实测信号的实验结果表明该算法较对比算法具有更高的压缩比和更低的重构误差,同时证明了其对采样频率和高斯白噪声具有较强的抗干扰能力。