MPEG(3) MPEG(3)
NAME
mpeg - 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 pre-
cise 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 accordingly, 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
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MPEG(3) MPEG(3)
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
hardware. When closed, the device waits for the last block
of data to display before returning to the application.
SOURCE
/os/pc/devmpeg.c
CONFIGURATION
mpeg0=port=0x1e0 irq=15 dma=6
SEE ALSO
mpeg(2), stream in sys-read(2)
DIAGNOSTICS
An error results on a write to the device once stopped.
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