Original Address: http://blog.yundiantech.com/?log=blog&id=4
The so-called video, in fact, will be a picture of a continuous put out, like, like a slide show, due to the inertia of the human eye, so the number of pictures as long as enough, you will think it is a continuous action. So, just to save pictures one by one down, so that you can form a video up.
However, due to the current limitations of network and storage space, direct store pictures is clearly not feasible. For example: in a video chat, assuming the acquisition of images from each camera the size of 200KB, sending about 15 images per second, per second required for such traffic will need to 3M (implies the need for a broadband 24M), it is clear that too much to ask.
So, we can consider these images compressed to reduce the size. And the video are basically two consecutive frame images not much difference. Thus, after recording a complete image Lower Dir after each image is only recorded on an image and not the same place, until there was a great difference image, only to re-record a complete image ( the complete image is called a key frame ). This can greatly reduce the space.
Compression jargon is called the above-mentioned video encoding , the current mainstream encoding format has ITU H.261, H.263, H.264, H.265, motion picture experts group is still M-JPEG and the International Organization for Standardization Moving picture Expert Group MPEG series of standards, in addition to the Internet on widely used as well as Real-Networks of RealVideo, Microsoft 's and Apple's QuickTime WMV and so on.
Encoding format so much, what should we choose? Through access to the information currently good choices are H.264,Therefore, H.264 only need to know on the line, we also follow the project all use H.264. H.264 San Liangxia details are not able to speak clearly, this text does not explain (keep after say), here introduced to H.264 What are the advantages:
1. Low bit rate (Low Bit Rate): and the like MPEG2 and MPEG4 ASP compression technique compared to the same video quality, the amount of data using H.264 compression technique is only 1/8, MPEG4 1/3 of the MPEG2.
2. High-quality images: H.264 can provide continuous, smooth, high-quality images (DVD quality).
3. Fault-tolerant capabilities: H.264 provides the necessary tools to solve easily occur in an unstable environment, packet loss and other network errors.
4. Network adaptability: H.264 provides a network abstraction layer (Network Abstraction Layer), so that the file can be easily H.264 is transmitted on different networks (e.g. Internet, CDMA, GPRS, WCDMA, CDMA2000, etc.).
5. High compression rate, H.264 compression ratio of amazing 102:1.
H.264 is the biggest advantage of a high data compression ratio, at the same picture quality, the compression ratio is 2 times or more H.264 MPEG-2 is 1.5 to 2 times of MPEG-4. For example, if the size of the original file is 88GB, using MPEG-2 compression standard compression into 3.5GB, 25:1 compression ratio, while the use of H.264 compression standard compression becomes 879MB, 879MB to 88GB from, H.264 compression ratio staggering 102:1. Low Bit Rate (Low Bit Rate) for high-compression H.264 is compared to an important role, and MPEG-2 and MPEG-4 ASP compression technology, etc. compared to, H.264 compression technology will save the user's download time and data traffic charges. It is particularly worth mentioning that, H.264 also has a smooth high-quality image while having a high compression ratio, and as such, after H.264 compressed video data in the network transmission process required less bandwidth, also more economical.
Original Address: http://blog.yundiantech.com/?log=blog&id=4