MPEG(3)MPEG(3)NAMEmpeg - Boffin mpeg decoder
SYNOPSIS
bind -b #E /dev
/dev/mpeg
/dev/mpegctl
DESCRIPTION
The mpeg device serves two files giving access to a Boffin MPEG-1
decoder.
The control file mpegctl when read returns lines of text giving the
device's properties. Each line starts video or audio followed by a
list of capabilities. The current device returns a fixed set:
video mpeg1,sif
audio musicam,I musicam,II
The control file accepts the following commands:
init Reinitialise the device's video and audio subsystems; cancel the
effect of stop or pause
stop Stop the display immediately.
pause Suspend display.
video iso11172 mpeg1,sif
Set the output video mode and formats; only this precise setting
is valid.
audio format rate
There are two choices for format: musicam,I (MPEG audio layer
1), with rate from 64000 to 448000 Hz, and musicam,II (MPEG
audio layer 2) with rate from 48000 to 384000.
window minx miny maxx maxy
Sets the overlay window on the screen, in screen coordinates.
If the window size exceeds 320x240, the image is scaled accord‐
ingly, separately in each dimension.
The data file mpeg is an exclusive-use device. Once the device has
been initialised and an output window set using the init and window
commands to the control file, and an audio format selected by the audio
command, MPEG data can be written in the agreed format to the mpeg
file, for display in the output window. The driver buffers the data
written and implements flow control between application and the hard‐
ware. When closed, the device waits for the last block of data to dis‐
play before returning to the application.
SOURCE
/os/pc/devmpeg.c
CONFIGURATION
mpeg0=port=0x1e0 irq=15 dma=6
SEE ALSOmpeg(2), stream in sys-read(2)DIAGNOSTICS
An error results on a write to the device once stopped.
MPEG(3)