Hi all.
I've noticed that most pocket TVs have LCDs with 320 x 234 pixels.
QVGA is 320x240, which are nice multiples of 16.
IIRC digital video has 720 luminance samples and 360 chroma samples on each line. I guess pocket TVs either discard some of the margin or resample the analogue video.
However I wonder how the transmitted video lines map onto 234 LCD lines?
Seems a peculiar number.
I have googled, but all I get is loads of links to pocket TVs or LCDs, and any technical details are buried.
The answer, is one LCD line to every other useable picture line in the incoming signal. Remember that standard US TV picture, with 525 nominal lines, only sends half of these on each frame (262/263 lines). Then at the top of the picture, is a quite long block of lines, allowing time for the frame retrace, and containing the teletext information (if broadcast), This leaves just under 240 'picture' lines on each retrace. Usually CRT's slightly overscan, losing two or three lines at the top and bottom of the frame, giving about 468 displayed image lines.
720*480, is the nominal full picture size of the image, excluding any allowance for the overscan. A similar allowance for overscan at the edges of the picture, and again only displaying alternate pixels, gives 320*234.Best Wishes
Have something to add? Share your thoughts — no account required.
Ask the community — no account required