From: Nielsen Linus (ext) <"Nielsen>
Date: Fri, 9 Aug 2002 12:41:04 +0200

> how big is the internal MP3 buffer in the MAS chip? i assume
> that it uses DMA to load in a new buffer from 'main' ram every
> time it runs out, but how often does it do this?

The MAS documentation doesn't tell how large the buffer is. It requests data
in about 30-40ms intervals, if I remember correctly.

> the reason I ask is that I want to try and implement a 'beep'
> when a remote control button is pressed. My idea is to overwrite
> the buffer in main ram with a 'beep' mp3 frame, and wait for it
> to be DMA'ed to the MAS chip.

This shouldn't be very hard to accomplish. Just reinit the DMA controller
with your new buffer and wait. Two problems arise:

1) There may be a delay of at least 20-30 milliseconds

2) The playing track will probably be disrupted, because of the loss of
sync, and the lost bit reservoir.

> Could we do something else to the MAS chip to feedback? like
> maybe set all bass/treble/loudness DSP settings to max for
> 1/10s to make it sound different for a bit?

You could try.

/Linus
Received on 2002-08-09