Comprehensive analysis of HD IP Camera technology

Comprehensive analysis of  technology

HD dubbed "title" in this era of rampant "HD", and you could see that in the end what is HD? What is megapixels ?
HD megapixels  is greater than 12FPS continuous acquisition the maximum resolution greater than 720P (1280 * 720), and even more than FullHD (1080p, resolution 1920 * 1080) to a higher 2048 × 1536 screen Webcams. Meet the definition of high definition above mentioned the HD index number of scan lines vertical and horizontal direction have reached 720P digital signal, can be understood as the HD products megapixels level.

General megapixels  than traditional analog cameras,  with the following advantages:

1, using the the megapixels level sensor, can get more video information, generally up to 1280 × 1024,1392 × 1024,1628 × 1236 or 2048 × 1536 resolution;
2, images of higher quality, better able to capture the details;
3, progressive scan CCD / CMOS dynamic performance of the screen is more fluid; 
4, can support the HDTV widescreen output mode (16:9);
5, wider coverage, the same monitoring area can replace the original multiple fixed point camera and an omnidirectional camera.

The camera's resolution depends on Sensor performance, CCD and CMOS two photosensitive chip CCD sensor in terms of sensitivity, resolution, noise control, high-quality image output, dynamic image performance is better than the COMS, so most of the professional camera select the CCD as the light-sensitive chip, and megapixels use Sony's most advanced the ICX series of photosensitive chip with low sensitivity illumination, to obtain a clearer image in a dark environment, ordinary camera can not be achieved.

Transmission, coding compression

Today, megapixels  signal transmission generally two kinds: one for the MONO / RAW transfer directly into digital signals by the analog-to-digital converter chip without any compression encoding transmitted over the network to transfer data directly to computer and computer-based means of disposing of the computer display, on behalf of products such as ProsilicaGC-Series Series, Baslerscout Series HD megapixel ; another coded transmission.

The network cameras coding compression

 encoding:

1.JPEG, MJPEG

JPEG compression technology can be said that the basis of all image compression technology. It is suitable for the compression of still images directly to deal with the whole picture, the compression ratio is 20-80 times, the resolution no choice. So have to wait until the completion of the entire compressed file transfer began decompressed image screen, this means to cause the transmission of a high-resolution screen to be time-consuming tens of seconds or even minutes.
While the MJPEG (MotionJPEG) in JPEG developed on the basis of the moving picture compression technology, it is only a frame compression, without substantially considering the change between the different frames in the video stream. Through this compression technique can obtain high-definition video images, and can be flexibly set the video resolution of each path, and compressed frames, and compressed picture can also be any splicing. But its flaws are obvious: First, frame loss is serious, real-time, while ensuring each channel must be under the premise of high-definition, it is difficult to perform real-time compression. Second, the compression efficiency is low, a larger storage space.
Later appeared multilayer the JPEG (ML-JPEG) compression technology, It has taken a gradient-based technology, the first transmission of low-resolution graphic, then supplemented send the more details of the compressed data, improve the picture quality. Although this way the time required for the original way. However, because you can see the screen, so the user will feel better this way.

2.MPEG-4

MPEG-4 was finalized in October 1998, to become an international standard in January 1999, followed by expansion purposes and the development of the second edition, the end of the end of 1999. Initially, MPEG-4 is mainly used in the Video Phone (VideoPhone sample), video email (VidoEmail,) and electronic news (Electronicnews), and other areas, which require a lower transmission rate, generally between 4800-64000bits/sec. The technology uses a very narrow bandwidth, frame reconstruction, compression and transfer the data, in order to get the best image quality with minimal data. MPEG-4 is characterized by its more suitable for interactive AV services and remote monitoring. This is an interactive dynamic image.
At present, MPEG-4 is mainly used in three areas: digital television, interactive graphics applications (including the contents of the synthetic techniques), interactive multimedia field. MPEG-4 standard technology so that it will be integrated into the product, classification, content access and process.

MPEG4 network video surveillance applications mainly include the following aspects:

Save storage space: video and audio all synchronization 40M - 120M / Road / h, which is 1/10 of the same quality MPEG1 or MJPEG; saving storage hard cost of inputs, and the latter part of the hard drive replacement costs;
Occupy less network bandwidth: the compression ratio is the same quality of MPEG1 and MJEPG of more than ten times, the occupied bandwidth in the network transmission is the same quality MPEG1 and MJEPG of 1/10. 64K bandwidth, the MPEG1 and MJEPG average can be transferred only to 1/2, MPEG4, within 5 - 7 will be substantial savings in transmission line rental charges;
3, the error recovery capability: network transmission bit error or packet loss, MPEG4 by the impact is small and can be quickly restored. BER of 1%, MPEG1 can not play MPEG4 only a slight edge blur; another example, when the network transmission packet loss by an instant phenomenon, MPEG1 recovery takes at least more than 10 seconds, and only 1 to MPEG4 3 seconds;
4, the image quality is high: the effect can be achieved close to DVD;
5, variable bandwidth: adjustable the network output rate from a 56K - 384K.

H.264
H.264 is the International Telecommunication Union (ITU-T) to develop a new generation of video compression formats. H.264 most valuable part of the higher data compression ratio. H.264 data compression ratio than this DVD system using MPEG-2 2 to 3 times higher than the MPEG-4 High 1.5 to 2 times the equivalent image quality. Because of that, after the H.264 compressed video data, the less the required bandwidth in the network during transmission, but also more economical. Match the MPEG-2 transmission rate of 6Mbps, H.264 requires only 1Mbps - 2Mbps transmission rate. H.264 get DVDForum and Blu-rayDiscAssociation, the adoption of a new generation HDDVD standard H.264 decoding algorithm is more complex calculation requires even higher than the WMA-HD. We know that the ATI from RadeonX1000 series, NVIDIA from the the series of GeForce6 most of the graphics by adding support for H.264 hardware decoding. Hass Hi-HD 3511 chip development megapixels  commonly used in the country, H.264BaselineProfile @ Level2.2 compression algorithm. HD megapixels  should be more advanced digital video products, high-quality, full-featured, should belong to the high-end products in the industry. Such resource consumption, different systems compatible equipment prices for various reasons have not caused more attention in the market.