HDCP (High-Bandwidth Digital Content Protection), which is a copyright protection mechanism for high-definition media content transmission such as DisplayPort, was jointly developed by Hollywood and Intel to prevent illegal copying and acquisition of data when it is transmitted through an interface. Although this kind of encryption security measures can prevent piracy to a certain extent, in practical applications, it has brought countless troubles to consumers because of the defects of its own verification mechanism. The most common one is the "handshake" between the source end and the receiving end. problem". Relevant vendors have put forward various design and testing methods to avoid such compatibility problems, but it seems to be frequently appearing on actual products, especially PC graphics cards.
This article refers to the address: http://
Recently, I encountered this kind of trouble when I connected my home theater with my friends using HTPC (Home Theater PC), AV amplifier and big screen TV. We first connected the HTPC to the amplifier with HDMI, and then the amplifier output HD video and audio to the TV and 5.1 channel speakers. Digital technology is free from the shackles of analog cables, requiring only two HDMI lines to complete high-definition video and 5.1-channel signal transmission. But when it started, the tragedy happened: the video clarity was so indescribable that each graphic had a dark edge similar to the USM (Unsharped Mask) algorithm; the video output aspect ratio was seriously wrong, and any modification would not help; Contrast, the color completely loses its level, and the noise is serious; horizontal scanning lines appear from time to time; any action of the input device (such as a mouse) causes the screen to be black and refreshed. The audio is even more unbearable, and the center channel output seems to be doing automatic gain control, and the sound is loud and small.
The above symptoms show that it is very likely that the HDCP handshake failed. In desperation, we turned all the appliances off and restarted several times before all functions returned to normal. Further testing found that the success of the HDCP handshake is closely related to the boot sequence. If the order is incorrect, all devices can only be restarted in the correct order. Many manufacturers claim that HDCP defects are considered in circuit design without the hot-swap "handshake problem", but unfortunately, practical experience tells us that the problem exists not only, but also very serious.
HDCP's "handshake problem" actually comes from the inherent flaws of its internal key authentication mechanism, as well as the lack of relevant specifications for device design. When a high-definition device such as a PC, a PS3, or a Blu-ray player outputs a signal to a display device through a high-definition interface, the source and the receiving end must be equipped with an HDCP key chip at the same time. Both parties have a key set that is encrypted and stored, and the key is used for encryption and decryption to ensure the connection is legal. After the HDMI is connected for the first time and recognized normally, the HDCP module at the source end and the terminal repeatedly authenticate each other to ensure that both ends of the cable are always legal authorized devices, so-called "handshake". The problem is that some devices take a time-based periodic scanning method, while others use an event-based interrupt mode. Different handshake modes cause frequent failures in actual operation, which seriously affects normal use. Sometimes the recognition process of HDCP is terminated unexpectedly due to the sleep of the TMDS decoding processor. Because of the problems of system power consumption and high-speed signal interference, devices such as ADC and TMDS decoding processor will be in a sleep state when they are not working. At this time, the transmission of high-definition signals will be turned off because the handshake process cannot be performed. .
The HDCP compatibility test is a necessary condition for ensuring a complete HD experience for multimedia devices, but it seems that the test project for PC products is still immature. According to the news, most of the HDMI products that are currently certified by HDCP are ordinary home appliances such as TV/displays and Blu-ray players with simple functions and simple data transmission methods. PCs are subject to many complicated factors such as graphics cards, operating systems, playback software, and optical drives. The impact was almost completely wiped out during the test. Due to the decline in price, HTPC, which integrates high-definition audio and video playback, Internet access, office, games and other functions, has been widely popularized. The improvement of HDCP testing of PC equipment has become a top priority. However, due to the excessive technology involved in PC products, a wide range of technologies have been realized. HDCP compatibility is in urgent need of collaboration among all vendors to agree on relevant designs and solutions.
best dc current sensor,best current sensor,ac current sensor,battery current sensor
Shanghai Zhilong Electronic Technology Co.,Ltd , https://www.zhilongsensor.com