有两个AMR格式音频文件，需要两个音频文件同时播放，也就是要对两个音频文件进行混频，生成一个AMR音频文件。
AMR有两种格式：AMR-NB和AMR-WB；使用的AMR格式为AMR-NB。
使用SOX软件进行混频，命令如下：
sox -m 1.amr-nb 2.amr-nb 3.amr-nb --combine mix-power
备注
1、这里需要修改.amr后缀为.amr-nb，否则SOX会出现报错：
sox FAIL formats: no handler for file extension `amr'
2、SOX选项--combine mix-power表示以同等功率混频
贴出SOX命令帮助说明：
sox: SoX v14.4.1
sox FAIL sox: Not enough input filenames specified
Usage summary: [gopts] [[fopts] infile]... [fopts] outfile [effect [effopt]]...
SPECIAL FILENAMES (infile, outfile): - Pipe/redirect input/output (stdin/stdout); may need -t -d, --default-device Use the default audio device (where available) -n, --null Use the `null' file handler; e.g. with synth effect -p, --sox-pipe Alias for `-t sox -'
SPECIAL FILENAMES (infile only): "|program [options] ..." Pipe input from external program (where supported) http://server/file Use the given URL as input file (where supported)
GLOBAL OPTIONS (gopts) (can be specified at any point before the first effect): --buffer BYTES Set the size of all processing buffers (default 8192) --clobber Don't prompt to overwrite output file (default) --combine concatenate Concatenate all input files (default for sox, rec) --combine sequence Sequence all input files (default for play) -D, --no-dither Don't dither automatically --effects-file FILENAME File containing effects and options -G, --guard Use temporary files to guard against clipping -h, --help Display version number and usage information --help-effect NAME Show usage of effect NAME, or NAME=all for all --help-format NAME Show info on format NAME, or NAME=all for all --i, --info Behave as soxi(1) --input-buffer BYTES Override the input buffer size (default: as --buffer) --no-clobber Prompt to overwrite output file -m, --combine mix Mix multiple input files (instead of concatenating) --combine mix-power Mix to equal power (instead of concatenating) -M, --combine merge Merge multiple input files (instead of concatenating) --magic Use `magic' file-type detection --multi-threaded Enable parallel effects channels processing --norm Guard (see --guard) & normalise --play-rate-arg ARG Default `rate' argument for auto-resample with `play' --plot gnuplot|octave Generate script to plot response of filter effect -q, --no-show-progress Run in quiet mode; opposite of -S --replay-gain track|album|off Default: off (sox, rec), track (play) -R Use default random numbers (same on each run of SoX) -S, --show-progress Display progress while processing audio data --single-threaded Disable parallel effects channels processing --temp DIRECTORY Specify the directory to use for temporary files -T, --combine multiply Multiply samples of corresponding channels from all input files (instead of concatenating) --version Display version number of SoX and exit -V[LEVEL] Increment or set verbosity level (default 2); levels: 1: failure messages 2: warnings 3: details of processing 4-6: increasing levels of debug messages FORMAT OPTIONS (fopts): Input file format options need only be supplied for files that are headerless. Output files will have the same format as the input file where possible and not overriden by any of various means including providing output format options.
-v|--volume FACTOR Input file volume adjustment factor (real number) --ignore-length Ignore input file length given in header; read to EOF -t|--type FILETYPE File type of audio -e|--encoding ENCODING Set encoding (ENCODING may be one of signed-integer, unsigned-integer, floating-point, mu-law, a-law, ima-adpcm, ms-adpcm, gsm-full-rate) -b|--bits BITS Encoded sample size in bits -N|--reverse-nibbles Encoded nibble-order -X|--reverse-bits Encoded bit-order --endian little|big|swap Encoded byte-order; swap means opposite to default -L/-B/-x Short options for the above -c|--channels CHANNELS Number of channels of audio data; e.g. 2 = stereo -r|--rate RATE Sample rate of audio -C|--compression FACTOR Compression factor for output format --add-comment TEXT Append output file comment --comment TEXT Specify comment text for the output file --comment-file FILENAME File containing comment text for the output file --no-glob Don't `glob' wildcard match the following filename
AUDIO FILE FORMATS: 8svx aif aifc aiff aiffc al amb amr-nb amr-wb anb au avr awb caf cdda cdr cvs cvsd cvu dat dvms f32 f4 f64 f8 fap flac fssd gsm gsrt hcom htk ima ircam la lpc lpc10 lu mat mat4 mat5 maud mp2 mp3 nist ogg paf prc pvf raw s1 s16 s2 s24 s3 s32 s4 s8 sb sd2 sds sf sl sln smp snd sndfile sndr sndt sou sox sph sw txw u1 u16 u2 u24 u3 u32 u4 u8 ub ul uw vms voc vorbis vox w64 wav wavpcm wv wve xa xi PLAYLIST FORMATS: m3u pls AUDIO DEVICE DRIVERS: alsa
EFFECTS: allpass band bandpass bandreject bass bend biquad chorus channels compand contrast dcshift deemph delay dither divide+ downsample earwax echo echos equalizer fade fir firfit+ flanger gain highpass hilbert input# ladspa loudness lowpass mcompand mixer* noiseprof noisered norm oops output# overdrive pad phaser pitch rate remix repeat reverb reverse riaa silence sinc spectrogram speed splice stat stats stretch swap synth tempo treble tremolo trim upsample vad vol * Deprecated effect + Experimental effect # LibSoX-only effect EFFECT OPTIONS (effopts): effect dependent; see --help-effect
