Protecting Against Card Corruption and Read Fatigue

A typical digital signage application often includes an “attract” video loop. If this video is fairly short, then a small number of flash blocks will be used repeatedly. Over time, the frequency with which these flash blocks are read may trigger “read fatigue errors” because the controller chips on certain microSD/SD cards are not designed to correctly handle and eliminate them.

The result is that some cards begin to fail after only 30,000 or 40,000 read cycles. If you have a video presentation that loops all day, every day, some cards may begin to fail a few months after purchase.

MLC AND TLC

BrightSign microSDHC cards use a type of NAND flash technology that is less susceptible to read errors than many other card brands. Many SD card manufacturers use “triple-level” (TLC) flash chips, which are more vulnerable to read issues than the “multi-level” (MLC) flash chips that BrightSign cards use. MLC flash chips provide faster write performance and greater reliability.

Read Speed

Most (if not all) SD cards currently on the market have sufficient read speed for digital sign and kiosk applications that use standard definition video, which in general requires cards that can sustain read rates of above 3 megabytes per second. However, high-definition videos (720p and 1080p) require a read rate of at least 4 megabytes per second, and this requirement is increased if you want to play 4K video (2160p) or two 4K/HD videos at once.

BrightSign microSDHC cards are rated at Class 10, which is sufficient for all of the above applications.