[Asterisk-Users] G.729a beta codec on old Pentiums

[andrewg at felinemenace.org]

On Sat, May 22, 2004 at 03:07:14PM +1000, Christopher Lee wrote:
> > Okay, doesn't mean so much to me, but it might help someone.
> 
> Nor I. I've posted the results to the RT ticket I've already got open with
> Digium support in case it helps them as well.
> 
> > > (gdb) x/5i $eip
> > > 0x4044e862 <lsp_get_quant+210>: fcomi  %st(5),%st
> > > 0x4044e864 <lsp_get_quant+212>: jbe    0x4044eb40 <lsp_get_quant+944>
> > > 0x4044e86a <lsp_get_quant+218>: fsubr  %st,%st(2)
> > > 0x4044e86c <lsp_get_quant+220>: faddp  %st,%st(1)
> > > 0x4044e86e <lsp_get_quant+222>: fxch   %st(1)
> 
> I'm wondering did this gdb command return the last 5 assembler instructions
> to execute before the program crashed?

$eip points to the instruction that was a problem, and x/5i prints out 5
instructions from $eip.

You could try disas lsp_get_quant in gdb and see if it uses the f* 
instructions before, because I can vaguely remember something about needing
to initialise something before using them. *shrug*

> 
> I did some searching for Pentium x86 instructions, and fcomi, fsubr, faddp,
> and fxch are all FPU instructions, so perhaps the module is indeed bombing
> out in the old Pentium FPU.
>

I vaguely recall the kernel having support for maths stuff (emulating it),
but I only thought that was a problem on very old computers.

> But as above, I really don't know enough about the nitty gritty of GNU
> debugger and x86 assembler to fully appreciate what I'm looking at so
> perhaps I should leave it to the experts from here :-)
> 
> If anyone has the beta G.729a codec successfully running on a Pentium (with
> or without MMX) CPU of similar vintage please drop me a line and let me
> know, as then I can rule out the machine itself and look harder at figuring
> out why my particular Asterisk installation isn't working.
> 
> Cheers,
> Chris Lee
> 
> 
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