The LC3 is an efficient low latency audio codec.
Low Complexity Communication Codec
The directory layout is as follows :
The default toolchain used is GCC. Invoke
make to build the library.
$ make -j
liblc3.a will be found in
The cc, as, ld and ar can be selected with respective Makefile variables
LD selections are optionnal, and fallback to
CC selection when not defined.
LIBC must be set to
bionic for android cross-compilation. This switch prevent link with
rt libraries, that is included in the bionic libc.
Following example build for android, using NDK toolset.
$ make -j CC=path_to_android_ndk_prebuilt/toolchain-prefix-clang LIBC=bionic
Compiled library will be found in
Tools can be all compiled, while involking
make as follows :
$ make tools
The standalone encoder
elc3 take a
wave file as input and encode it according given parameter. The LC3 binary file format used is the non standard format described by the reference encoder / decoder tools. The standalone decoder
dlc3 do the inverse operation.
elc3 -h or
dlc3 -h for options.
elc3 output bitstream to standard output when output file is omitted. On the other side
dlc3 read from standard input when input output file are omitted. In such way you can easly test encoding / decoding loop with :
$ ./elc3 <in.wav> -b <bitrate> | ./dlc3 > <out.wav>
aplay tools, you will be able to instant hear the result :
$ ./elc3 <in.wav> -b <bitrate> | ./dlc3 | aplay
A python implementation of the encoder is provided in
test diretory. The C implementation is unitary validated against this implementation and intermediate values given in Appendix C of the specification.
# apt install python3 python3-dev python3-pip $ pip3 install scipy numpy
$ make test
The proposed encoder and decoder implementation have been fully tested and validated.
For more detail on conformance, refer to Bluetooth Conformance Documents and scripts
The codec was here subjectively evaluated in a blind listening test.
Meson build system is also available to build and install lc3 codec in Linux environment.
$ meson build $ cd build $ ninja $ sudo ninja install