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mpeg - Boffin mpeg decoder


bind -b #E /dev



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:

Reinitialise the device's video and audio subsystems; cancel the effect of stop or pause
Stop the display immediately.
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 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 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.




mpeg0=port=0x1e0 irq=15 dma=6


mpeg(2), stream in sys-read(2)


An error results on a write to the device once stopped.

MPEG(3 ) Rev:  Tue Mar 31 02:42:38 GMT 2015