The LC3 is an efficient low latency audio codec.
Low Complexity Communication Codec
The directory layout is as follows :
- include: Library interface
- src: Source files
- tools: Standalone encoder/decoder tools
- build: Building outputs
- bin: Compilation output
The default toolchain used is GCC. Invoke make to build the library.
make -jCompiled library liblc3.a will be found in bin directory.
The cc, as, ld and ar can be selected with respective Makefile variables CC,
AS, LD and AR. The AS and LD selections are optionnal, and fallback
to CC selection when not defined.
The LIBC must be set to bionic for android cross-compilation. This switch
prevent link with pthread and 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=bionicCompiled library will be found in bin directory.
Tools can be all compiled, while involking make as follows :
make toolsThe 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.
Refer to elc3 -h or dlc3 -h for options.
Note that 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>Adding Linux aplay tools, you will be able to instant hear the result :
./elc3 <in.wav> -b <bitrate> | ./dlc3 | aplayencode original.wav (16 bit, 48000 Hz)
mandatory flag:
- b : encoding output bitrate. values interval [16000; 320000]
other flags:
- m : Frame duration in ms (default 10)
- r : Encoder samplerate (default is input file samplerate). values {8000, 16000, 24000, 32000, 48000}
./elc3 -b <16000 - 320000> [-m <ms> -r {8000, 16000, 24000, 32000, 48000}] <in.wav> <out.lc3>./elc3 -b 48000 original.wav out.lc3decode out.lc3, decode can work without flags
flags:
- b : sample bit size (default 16) {16, 24}
- r : output samplerate (can be more than encoded samplerate) {8000, 16000, 24000, 32000, 48000}
./dlc3 [-b {16, 24} -r {8000, 16000, 24000, 32000, 48000}] <in.lc3> <out.wav>./dlc3 out.lc3 decoded48000.wav