Files
asterisk/codecs/gsm
Kevin P. Fleming 69255bd210 Merged revisions 207680 via svnmerge from
https://origsvn.digium.com/svn/asterisk/trunk

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  r207680 | kpfleming | 2009-07-21 08:28:04 -0500 (Tue, 21 Jul 2009) | 18 lines
  
  Merged revisions 207647 via svnmerge from 
  https://origsvn.digium.com/svn/asterisk/branches/1.4
  
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    r207647 | kpfleming | 2009-07-21 08:04:44 -0500 (Tue, 21 Jul 2009) | 12 lines
    
    Ensure that user-provided CFLAGS and LDFLAGS are honored.
    
    This commit changes the build system so that user-provided flags (in ASTCFLAGS
    and ASTLDFLAGS) are supplied to the compiler/linker *after* all flags provided
    by the build system itself, so that the user can effectively override the
    build system's flags if desired. In addition, ASTCFLAGS and ASTLDFLAGS can now
    be provided *either* in the environment before running 'make', or as variable
    assignments on the 'make' command line. As a result, the use of COPTS and LDOPTS
    is no longer necessary, so they are no longer documented, but are still supported
    so as not to break existing build systems that supply them when building Asterisk.
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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.0@207683 65c4cc65-6c06-0410-ace0-fbb531ad65f3
2009-07-21 13:39:44 +00:00
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GSM 06.10 13 kbit/s RPE/LTP speech compression available
--------------------------------------------------------

The Communications and Operating Systems Research Group (KBS) at the
Technische Universitaet Berlin is currently working on a set of
UNIX-based tools for computer-mediated telecooperation that will be
made freely available.

As part of this effort we are publishing an implementation of the
European GSM 06.10 provisional standard for full-rate speech
transcoding, prI-ETS 300 036, which uses RPE/LTP (residual pulse
excitation/long term prediction) coding at 13 kbit/s.

GSM 06.10 compresses frames of 160 13-bit samples (8 kHz sampling
rate, i.e. a frame rate of 50 Hz) into 260 bits; for compatibility
with typical UNIX applications, our implementation turns frames of 160
16-bit linear samples into 33-byte frames (1650 Bytes/s).
The quality of the algorithm is good enough for reliable speaker
recognition; even music often survives transcoding in recognizable 
form (given the bandwidth limitations of 8 kHz sampling rate).

The interfaces offered are a front end modelled after compress(1), and
a library API.  Compression and decompression run faster than realtime
on most SPARCstations.  The implementation has been verified against the
ETSI standard test patterns.

Jutta Degener (jutta@cs.tu-berlin.de)
Carsten Bormann (cabo@cs.tu-berlin.de)

Communications and Operating Systems Research Group, TU Berlin
Fax: +49.30.31425156, Phone: +49.30.31424315

--
Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
Universitaet Berlin.  See the accompanying file "COPYRIGHT" for
details.  THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.