[Speex-dev] Speex decode memory usage on an Arm processor (wideband)

[tom abcd]

I am hoping to use Speex for a embedded project using Philips Arm processor
(50 mips) 512kb flash 32kb ram.  I found in the manual that decode takes
about 0.5 mips so I should have enough processing power and I compiled the
lib and it seems to take less then 64K so the only issue is memory usage.  I
have been testing the speex decode on windows looking at the stack usage and
how much is malloc.  There appear to be three defines that control much of
the memory usage: MAX_CHARS_PER_FRAME , SB_DEC_STACK and NB_DEC_STACK.

I have tested lowering these values and then running the speexdec program
and looking for errors.  By trial and error it appears that I can lower
MAX_CHARS_PER_FRAME  = 750,   SB_DEC_STACK = 750*sizeof(spx_sig_t)  and
NB_DEC_STACK = 250*sizeof(spx_sig_t)
and not get any memory errors but have no idea if these are safe values or
not.  I could not tell how much stack spaced was used but would guess 4 kb
would be enough.   After making these changes it appears to Alloc less the
16kb.

So any pointers on what is the min memory needed for wideband decode on a
ARM process?  Can it all be done in 20 kb or less?  Any suggestions on what
choices cause more memory usage?

I will control how the files are compressed and I am not using the Ogg file
structure but just the simple count data approach given in the manual
example.  I also notice that the Speexdec win32 example skips some of the
first bytes from the decode process.  It seems to be using the LOOK_AHEAD
amount but I can not find anything in the manual about this.   So is some of
the first data out of the decode not used?


Thanks in advance.
Tom
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