[speex-dev] XScale realtime encoding possible?

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Thu Nov 6 08:59:51 PST 2003


I have replaced most (but not all) of the float operations by integer
operations, but it seems like the remaining ones take a long long time
when emulated in kernel space (hence high system time). The other
problem is that I don't have access to an ARM-based device (anyone wants
to send me one?), so I'm doing all this blind... If you'd like to help,
it can also accelerate things.

The other thing is that you're probably pushing a bit too much with 44.1
kHz, which would probably require around 250 MIPS even with the
fixed-point completed. It could probably run in real-time but it would
take lots of CPU and require asm optimizations. I suggest you try
something like 16 kHz. I'm sure the quality will still be enough for you
(much better than MP3 at 24 kbps anyway :)

Last thing, can you try the code that's in CVS right now? I removed many
float ops since 1.1.1, so it may already work better. 


<p>Le jeu 06/11/2003 à 10:29, MAL a écrit :
> Hi all,
> I've got a 400MHz XScale-PXA255 board, and I want to stream voice from 
> it over a network connection at 28.8baud.  This calls for a capable 
> voice encoder which can encode at about 24kbps.  I was damn happy when I 
> found Speex and said goodbye to MP3 :)
> However, i'm still a long way from realtime encoding using speexenc, is 
> this possible?
> Using the fixed point math option in 1.1.1 (the XScale has no floating 
> point unit), and compiling with CFLAGS="-O3 -funroll-loops -ffast-math", 
> I get the following:
> time speexenc -u --quality 0 --abr 28 --comp 1 test.wav test.spx
> Warning: Speex is only optimized for 8, 16 and 32 kHz. It will still 
> work at 44100 Hz but your mileage may vary
> Encoding 44100 Hz audio using ultra-wideband (sub-band CELP) mode (mono)
> real    0m42.345s
> user    0m7.660s
> sys     0m34.690s
> The input file is 44.1KHz, 32bit mono, but I would be perfectly happy to 
> use 32KHz, 16bit, if that would make any impact on speed?
> Any help would be much appreciated.
> Thanks,
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Jean-Marc Valin, M.Sc.A., ing. jr.
LABORIUS (http://www.gel.usherb.ca/laborius)
Université de Sherbrooke, Québec, Canada

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