/dev/viddata
/dev/vidctl
/dev/vidcram

The control device vidctl accepts the following commands:

on

Disable LCD panel (if present) and enable output from the video frame buffer.

off

Stop display from the video frame buffer and re-enable the LCD panel (if present).

mode m

Set the video output format to m, which is one of: ntsc, pal-i, pal-m or pal-n. This command is only effective when video output is off. When next switched on, the both the video controller RAM and ADV7176 are reprogrammed to the new format.

Video data can be written to the video frame buffer by writes of the viddata file. The file offset selects the starting byte within the frame buffer. Reads return the corresponding data from the frame buffer. The application is responsible for formatting the data as the 823's video encoder requires, for the selected video format.

The file vidcram gives read and write access to the contents of the video control RAM. The file offset addresses bytes in the RAM; values can be read from or written to the RAM in groups of 4-byte big-endian words.