libgsm1-dev binary package in Ubuntu Bionic amd64

 This package contains header files and development libraries for
 libgsm, 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.

Source package