Linux Driver Documentation

Driver Interfaces

The VideoPlex Xpress Linux device driveris based on the driver written by Pauline Middelink. The standard video for the Linux (V4L) interface has not been changed. Standard V4L players and applications will work with the VideoPlex XPress card. Most changes are in the Vaddis.c and Vaddis.h files that add /dev/decoder* devices and various ioctls.

To recieve an MPEG stream, the VideoPlex XPress Linux driver uses device files in the form of /dev/decoder?_x_y.
'?' stands for the number of the board.
'x' stands for the video sample rate (PAL or NTSC).
'y' stands for the audio sample rate (32, 44, 48).
For example, if the MPEG file 'example.mpg' is PAL encoded and audio sampled at 48 KHz, you can play it back with:

cat example.mpg /dev/zeroes > /dev/decoder0_pal_48.

In order to flush the MPEG file properly, it is necessary to append zeros to the end of the file. After the MPEG file has finished playing, the file descriptor will close with the EPIPE error. This is a correct way to play from command line.
The VPXpress.h file contains various ioctls that allow you to control the VideoPlex Xpress. The VideoPlex Xpress Linux SDK documents these ioctl controls.

OSD Support

The VideoPlex Xpress Linux device driver supports OSD (On Screen Display). The OSD feature in the Linux driver uses /dev/decoder?_osd file abstract (where, '?' stands for the number of the board). To display a bitmap, a properly formatted file should be written to the decoder's OSD device. For example,

cat file.osd > /dev/decoder0_osd

The VPXpress.h file contains various ioctls that allow you to control the OSD. These ioctls and the format of the OSD bitmap are documented in VideoPlex XPress Linux OSD SDK Package

Limitations