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    如何入门音视屏

    保存视频的每一帧,每一个像素没要必要,而且也是不现实的,因为这个数据量太大了,以至于没办法存储和传输,比如说,一个视频大小是 1280×720 像素,一个像素占 12 个比特位,每秒 30 帧,那么一分钟这样的视频就要占 1280×720×12×30×60/8/1024/1024=2.3G 的空间,所以视频数据肯定要进行压缩存储和传输的。 而可以压缩的冗余数据有很多,从空间上来说,一帧图像中的像素之间并不是毫无关系的,相邻像素有很强的相关性,可以利用这些相关性抽象地存储。同样在时间上,相邻的视频帧之间内容相似,也可以压缩。每个像素值出现的概率不同,从编码上也可以压缩。人类视觉系统(HVS)对高频信息不敏感,所以可以丢弃高频信息,只编码低频信息。对高对比度更敏感,可以提高边缘信息的主观质量。对亮度信息比色度信息更敏感,可以降低色度的解析度。对运动的信息更敏感,可以对感兴趣区域(ROI)进行特殊处理。 视频数据压缩和传输的实现与最终将这些数据还原成视频播放出来的实现是紧密相关的,也就是说视频信息的压缩和解压缩需要一个统一标准,即音视频编码标准。

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    IDA Pro 7.5 + HexRays (x86/x64/ARM/ARM64)

    The source code of the software we use on a daily basis isn’t always available. A disassembler like IDA Pro is capable of creating maps of their execution to show the binary instructions that are actually executed by the processor in a symbolic representation called assembly language. This disassembly process allows software specialists to analyse programs that are suspected to be nefarious in nature, such as spyware or malware. However, assembly language is hard to read and make sense of. That is why advanced techniques have been implemented into IDA Pro to make that complex code more readable. In some cases, it is possible to revert the binary program back, to a quite close level, to the original source code that produced it. The map of the program’s code can then be post-processed for further investigation.

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