This code was downloaded from here
and is based on 26304-f00.zip release.
Floating-point implementation -> http://www.3gpp.org/ftp/Specs/archive/26_series/26.304/
Fixed-point implementation -> http://www.3gpp.org/ftp/Specs/archive/26_series/26.273/
3GPP file format -> http://www.3gpp.org/ftp/Specs/archive/26_series/26.412
I would love to port this to FFmpeg (assuming no licensing issues...) - looking for FFmpeg mentors!
$ wget http://www.music.helsinki.fi/tmt/opetus/uusmedia/esim/a2002011001-e02-16kHz.wav
$ wine encoder.exe -rate 16 -if a2002011001-e02-16kHz.wav -of out.3gp
3gp File Format
Encoding @ 16.00kbps
--- Running ---
$ mediainfo out.3gp
General
Complete name : out.3gp
Format : MPEG-4
Format profile : 3GPP Media Release 6 Basic
Codec ID : 3gp6 (3gp6/isom)
File size : 110 KiB
Duration : 54 s 160 ms
Overall bit rate mode : Constant
Overall bit rate : 16.7 kb/s
Encoded date : UTC 2017-02-10 06:10:58
Tagged date : UTC 2017-02-10 06:10:58
Audio
ID : 1
Format : sawp
Codec ID : sawp
Duration : 54 s 160 ms
Bit rate mode : Constant
Bit rate : 16.2 kb/s
Channel(s) : 2 channels
Sampling rate : 6 464 Hz
Bit depth : 16 bits
Stream size : 107 KiB (97%)
Encoded date : UTC 2017-02-10 06:10:58
Tagged date : UTC 2017-02-10 06:10:58
$ wine decoder.exe -if out.3gp -of out.wav
...
File type brand '3gp6' minor version 256
Compatible brands: 'isom' (yes) '3gp4' (no) '3gp5' (no)
Track 1 'sawp' Duration 54.160s Time scale 72000
Decoding @ 16.00kbps
$ mediainfo out.wav
General
Complete name : out.wav
Format : Wave
File size : 9.92 MiB
Duration : 54 s 160 ms
Overall bit rate mode : Constant
Overall bit rate : 1 536 kb/s
Audio
Format : PCM
Format settings, Endianness : Little
Format settings, Sign : Signed
Codec ID : 1
Duration : 54 s 160 ms
Bit rate mode : Constant
Bit rate : 1 536 kb/s
Channel(s) : 2 channels
Sampling rate : 48.0 kHz
Bit depth : 16 bits
Stream size : 9.92 MiB (100%)