Sunday, October 02, 2011

Car Digital Video recorder - Black box

There are tons of such product in the market and I can roughly categorize them according to the compression chips :
1) Low resolution 640x480 products (Some may cheat to increase pixels to 1280x960, with worst quality) ; price range from HKD 200-$400 ; The latest product even cheats by claiming having 720p/HD quality / with HDMI output , but you can tell from the jerky preview on the LCD (if you can test before buy) . THese fake product line can be made to look exactly the same as other high end product.
2) 720p : The chipset is from Z0ran with real 1280x720 quality. The colour saturation of this chip is good.
Another 720p chip is from NOVATEK. The cam manufacturer upscale it and claim  having 1440x1080/ 1920x 1080 video output, but at 15 fps, which is almost useless in reality. The colour saturation is good. Bitrate is around 6,000 bps. Product of this line market at range of HKD 600-980.
3) Genuine 1080p compression chips: Ambarella chip. capable to produce Full HD video of 30fps. The picture quality reveals lot more details than 720p, but looks soft in contrast and colour saturation. Most cam has bit rate of around 8,000 bps and this is the limiting factor of the performance of this camera. The optical resolution is also another limiting factor, as wide angle (120deg) will lost much details especially at the edge..The price of this product range over HKD $1100 - 1600 (DOD)

Below is the inside of a fake DOD F990 "Full HD" camera (Full HD only @15fps, though most seller claim it is 30fps and you must test it before buying). The button on the top makes lots of rattling noise when recording and you need to tap them.


 The compression chip Novatek is only 720p and is the same class as Zoran chips.
 CMOS housing