Rockbox mail archive
Subject: Re: MP3Buffer?
From: George Styles (george_at_ripnet.co.uk)
----- Original Message -----
From: "Nielsen Linus (ext)" <Linus.Nielsen_at_elema.siemens.se>
Sent: Friday, August 09, 2002 11:41 AM
Subject: RE: MP3Buffer?
> > 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
> 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.
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