[Rpcemu] Code not working correctly on RPCEmu

Timmermans, Andre andre.timmermans at atos.net
Sun Feb 26 10:37:53 PST 2012


I have included an archive for testing.

The BASIC code Filter conrains some assembler code
which takes the file IN and produces a file OUT
so it is better set te CSD before running it.

The non-recompiling version of RPCEmu produces a file identical
to OUR_REF (te output on my RPC). The recompling version
does not. Since most of the time the filter seems to work fine
in the player that uses it (the sound seems OK), I am wondering
if the small amplitude of the signed 16-bit input samples
combined to the 24-25 bits in size filter parameters
puts them right on the 32-bit boundary and I am wondering
if it is not the 64bit addition part of the SMLAL which
is not emulated correctly (i.e. is the carry transmitted
correctly from the addition of the lower 32-bit registers
To the upper 32-bits?).

Kind Regards,

> -----Original Message-----
> From: mhowkins at gmail.com [mailto:mhowkins at gmail.com] On 
> Behalf Of Matthew Howkins
> Sent: jeudi 23 février 2012 19:32
> To: Timmermans, Andre
> Cc: rpcemu at riscos.info
> Subject: Re: [Rpcemu] Code not working correctly on RPCEmu
> > I have just added support for Impulse Tracker's resonant filters
> > in my TimPlayer module and tought I'd try it on RPCEmu too.
> > On most of the files it sound just te same as on a real RPC
> > but in a few cases note on which the filter is applied becomes
> > garbage. As the equalizer uses not too dissimilar in form
> > (y0 = a0 * x0 + a1 * x1 + a2 * x2 + b1 * y1 + b2 * y2)
> > I tried using it on a normal song and bingo, the sound becomes
> > completely distorted.
> Can you provide a simple runnable example that demonstrates 
> the problem clearly?
> Please provide a copy of the rpclog.txt file from a setup 
> showing the problem.
> With those I am confident I could track down the fault quickly. Trying
> to study the problem from the code provided will be much harder.
> Thanks
> Matthew
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