Testing requirements of smart multimedia video
Testing of smart multimedia video has grown from analyzing captured image quality to various items and supports specifications including EDID (Extended display identification data)/DDC, HDCP (High Definition Content Protection) and PSNR (Peak Signal to Noise Ratio) and OCR (Optical character recognition) etc. Through the aforementioned tests and standards, video transmission performance and accuracy can be made more consistent for a higher quality product
- EDID/DDC support (Plug & Play system):
EDID (Extended display identification data) is usually kept at the display end EEPROM, which stores resolution and scanning frequency, as well as device brand and serial numbers, supported by the display device.
DDC (Display Data Channel) is a standard specification launched by VESA that informs both sender and receiver of the other’s capacity. Once the display end's EDID data is received at the host, the display and host communicate through the DDC channel to establish the appropriate resolution. This Plug & Play system enables the host and display to detect and set the ideal resolution to avoid manual adjustment by the user.
EDID/DDC’s support of commercially available devices with an advanced image capture card for testing is increasingly important. If the existing EDID / DDC configuration fails to comply with the testing device, the editing and updating capacity of EDID/ DDC are crucial considerations for versatility and expandability.
- HDCP (High Definition Content Protection) support:
Developed by Intel, HDCP is aimed at preventing illegal copying or recording of digital videos when transmitted through HDMI or DVI interfaces. The HDCP mechanism requires both source and display ends to be equipped with built-in HDCP key chips to display any HDCP protected video content, otherwise the user will only see videos with reduced image quality or noisy image. To test HDCP encrypted video content, the image capture card used by the testing equipment must have a HDCP key chip built in.
- PSNR (Peak Signal to Noise Ratio) testing:
PSNR is a popular and widely accepted objective image quality evaluation measure based on the ratio of maximum image signal value vs. noise contained in the image. The higher the PSNR value the better the image quality will be. In general, a PSNR value lower than 30dB represents unacceptable image quality. That is, the PNSR value must exceed 30dB in most cases. Only uncompressed images of high resolution and frequency can help testing equipment owners use the PSNR algorithm for automatic image testing once the image data is acquired.
- OCR (Optical character recognition) testing:
Smart multimedia devices are characterized by their cloud-based remote monitoring & control services. That is, smart multimedia devices rely on networks to fulfill their functions, such as storing data and accessing apps. The device and its display screen must have WiFi streaming for wireless multimedia video playback. As such, the WiFi data, such as IP address and transmission volume, are mandatory testing items. IP address and transmission volume checks were done manually in the past, which often led to unstable results due to inaccurate and/or slow testing processes. Identifying characters with the OCR function improves testing performance significantly by immediately detecting any WiFi data transmission abnormality.