Key words:
264, Hi3510, codec, design, implementation
With a new type of consumption such as digital TV, DVD player, digital still image camera (DSC), DVD player, Digital Station Camera (DSC), Digital Video Recorder (DVC), etc., support digital audio and video processing The number of electronic devices has also continued to rise quickly. The huge information flow has brought rich human culture and also brought the troubles of storage information. In particular, the huge data of video information has spawned the demand for video compression technology. Video compression technology has become one of the most popular technologies in the Multimedia Age, and is widely used in the fields of television, movies, visual calls, video conferencing, remote monitoring and other fields.
1 H.264 Introduction
H.264 is the latest coding standard established by ITU-T and ISO / IEC. It is first proposed by ITU-T in 1997. The goal is to propose a higher performance (relative to H.263) video coding at the time. standard. H.264 has the following features relative to other standards:
(1) Low bit rate. Compared with MPEG-2 and other compression techniques, the amount of data after the compression of H.264 is only 1/2 ~ 1/3 of the MPEG-2 in the same image quality. Obviously, H.264 compression technology will greatly save storage capacity, channel bandwidth, and user download time and data traffic charges.
(2) High image quality. H.264 provides continuous, smooth high quality images.
(3) Wide application range. Different PROFILEs of H.264 can be applied to real-time communication with strict time delay, or other applications that are not high in delay (such as video storage, streaming, etc.).
(4) Robust. H.264 In design, the corresponding tools are proposed for packet losses and wireless networks in the packet switched network, such as the packet loss and wireless networks, so that H.264 has stronger anti-comment performance when propagating in these networks.
(5) Friendly of various networks. The NAL layer is added to H.264, which is responsible for assembling the encoder's output code stream to various types of networks, providing a friendly network interface.
The reason why H.264 can reach the above performance is because of the following advanced technologies:
The first is the intra predictive encoding, and the image null domain correlation is taken to reduce the code rate. Depending on the type of image coding, each macroblock can choose one of several coded types. There are 13 prediction modes (4 × 4 blocks of 9 prediction modes, 16 x 16 blocks 4 prediction modes), which are not in the previous standard.
The second is to adopt a new fast motion valuation algorithm umhexagons (China Patent), which is a new algorithm for saving more than 90% of the rapid full search algorithm in H.264, full name called "asymmetric cross Unsymmetrical-Cross Muti-HEXAGON SECH, is a whole pixel motion estimate algorithm. Since it is encoded in high-yard larger motion image sequence, the amount of operation is very low under conditions that maintain a better distortion rate performance, and has been officially adopted by H.264. H.264 has 7 block matching mode, calculated one by one, selecting optimal. For example, a finer portion is 4 × 4 blocks, and the non-moving background can be used for 16 × 16 blocks. The previous standard is only one or two block size patterns. H.264 uses multi-frame references to maximize field dependence. Reference frames can range from 1 frame to 15 frames, and the conventional criteria are single frame references. There is also a 1/4 or 1/8 precision of sub-pixel motion estimation, and the standard is used in the previous standard to search for 1/2 precision sub-pixel search, and is not a must option. In order to eliminate the block effects that often appear in the video coding, H.264 uses the deck effect filter.
H.264 also uses an integer DCT transformation to increase the transformation speed, using a new entropy encoding method such as CAVLC, Cabac to improve the encoding effect.
The H264 standard enables moving image compression techniques to a higher stage, providing high quality image transfer on lower bandwidth is a highlight of H.264. H.264 Due to a lower transfer bit rate and low in storage, the basic system does not need to use copyright, which has open nature, is now expected to replace MPEG-2.
2 Hi3510 working principle
Hi3510 is a video compression chip based on H.264 BP algorithm, which is introduced by Haisi. The chip uses the multi-core high integration of the ARM + DSP + hardware acceleration engine, with powerful video processing functions. Real-time coding of DVD quality can be achieved, can adapt to various network environments, ensuring clarity and real-time, low-rate H.264 encoding technology greatly reduces network storage, and adds DES / 3DES. The decryption hardware engine ensures network security.
The Hi3510 is used in a 0.13μm process, the LFBGA400 package, the size of 19 × 19mm, the pin spacing is 0.8mm, the interior integration includes digital video interface, USB, ETH, I2S, I2C, GPIO, SPI, UART, SDRAM, DDR and other interfaces To meet the development of various application scenarios, it can greatly reduce the BOM cost of the equipment.
Hi3510 Working: The video input unit receives digital video information output by VADC via the ITU-RBT.601 / 656 interface, and writes the received original image into the outer memory (SDR SDRAM or DDR SDRAM via the AHB bus; Video codec is read images from outside, performing motion estimation (inter prediction), intra prediction, DCT transformation, quantization, entropy encoding (CAVLC + Exp-golomb), IDCT transformation, inverse quantization, motion compensation, etc. Operation, it will eventually write to the outer memory in the bare code stream and coding reconstruction frame (reference frame of the next frame) in accordance with the H.264 protocol; the video output unit reads image data from the outside and passed ITU-R. The BT.601 / 656 interface is sent to VDAC for display. Different, the content of the video output unit is different from the image content read from the outside. When the input image is required, the video output unit reads from the outside. Original image, when you need to observe the encoding effect of the video encoder, the video output unit reads the encoded reconstructed frame from the outside; ARM is the package stream of the video encoder output, and then send it to the network port. To achieve video on demand services.
The H.264 audio and video codec of Hi3510 is shown in Figure 1, which is integrated with a rich peripheral interface by the ARM + DSP + video encoding accelerator + graphics engine zoom, integrated with a wealth of peripheral interfaces, including numbers Watermark, DES / 3DES algorithm, makes single-chip adapts to almost all work, reduces development difficulty with other chips, and exempts manufacturers to repeat the content of the standard part of the algorithm, which greatly reduces the entry threshold of equipment manufacturers. With the development kits of Haisi's different application forms, various products such as PMP, Visual Phone, Network Monitoring, PVR, Visual Intercom are available.
3 Hi3510 codec design plan
As the codec chip as a SOC architecture, the HI3510 is fully considered to compatibility and the convenience of use when designing. Support for almost all companies produced series of AD / DA chips. The HI3510 can be operated as a separate encoder or as a stand-alone decoder, or simultaneously coding work, fully considering the various applications of the codec market. The HI3510 is a typical multi-applied single-chip solution that greatly reduces the BOM composition and cost of the device.
The codec design is shown in Figure 2 while the HI3510 is shown.
4 Hi3510 codec application
The Linux operating system comes with the HI3510 (also supports open operating systems such as VxWorks, WinCe) and ARM processors, allowing the chip to achieve many rich application capabilities development in addition to codec function. In FIG. 2, the digital compression, storage, and transmission of the composite video signal can be realized as long as an ordinary AD is attached. The HI3510 development package provides a top-level API interface, you can call all chip functions and develop your own personalization.
The encoding application design of the HI3510 chip is shown in Figure 3.
The decoder application is the same as the encoder in the architecture (the convenience can maintain consistency, you can implement a hardware to meet different needs, just need software upgrade). The decoder only needs to match the DA chip (if the LCD number screen can save this chip), you can achieve the effect of decoding the data code stream, and implements a menu operation of the user's human machine interaction through the GUI or OSD, implementing a similar function such as PMP. Applications.
The decoding application design of the HI3510 chip is shown in Figure 4.
H.264 The application of the standard, providing technical support for the network transmission of the video, in particular low-bandwidth (such as wireless transmission mode). Today, in today's explosion, the market requires designers to launch a product faster, and in order to maintain product competitiveness, in product prices, product application features sufficient advantage, especially in the multi-coal market. Haisi's SOC chip is based on the standard algorithm, giving the designer's largest flexibility to design the right product, which greatly reduces the manufacturer's delivery cost, shorten the time of the manufacturer's launch new product, and prepares for the market. . In recent years, each portable personal electronic device seems to be equipped with audio and video functions, including mobile phones, portable media players, and PDAs. This high cost-effective H.264 codec, which is based on HI3510, will have a broad market prospect.
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