在github上搜索build-ffmpeg.sh即可，编译一般情况没有问题，但是在使用的过程中容易出问题，报如下错误
Undefined symbols for architecture x86_64:
"_AudioConverterDispose", referenced from:
_ffat_close_decoder in libavcodec.a(audiotoolboxdec.o)
_ffat_close_encoder in libavcodec.a(audiotoolboxenc.o)
"_AudioConverterFillComplexBuffer", referenced from:
_ffat_decode in libavcodec.a(audiotoolboxdec.o)
_ffat_encode in libavcodec.a(audiotoolboxenc.o)
"_AudioConverterGetProperty", referenced from:
_ffat_create_decoder in libavcodec.a(audiotoolboxdec.o)
_ffat_init_encoder in libavcodec.a(audiotoolboxenc.o)
"_AudioConverterGetPropertyInfo", referenced from:
_ffat_create_decoder in libavcodec.a(audiotoolboxdec.o)
_ffat_init_encoder in libavcodec.a(audiotoolboxenc.o)
"_AudioConverterNew", referenced from:
_ffat_create_decoder in libavcodec.a(audiotoolboxdec.o)
_ffat_init_encoder in libavcodec.a(audiotoolboxenc.o)
"_AudioConverterReset", referenced from:
_ffat_decode_flush in libavcodec.a(audiotoolboxdec.o)
_ffat_encode_flush in libavcodec.a(audiotoolboxenc.o)
"_AudioConverterSetProperty", referenced from:
_ffat_create_decoder in libavcodec.a(audiotoolboxdec.o)
_ffat_init_encoder in libavcodec.a(audiotoolboxenc.o)
"_AudioFormatGetProperty", referenced from:
_ffat_create_decoder in libavcodec.a(audiotoolboxdec.o)
"_AudioFormatGetPropertyInfo", referenced from:
_ffat_create_decoder in libavcodec.a(audiotoolboxdec.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
这个错误是由于缺少系统动态库造成的，找出_ffat_create_decoder对应的库名，逐个添加即可如：
FFmpeg: libavcodec/audiotoolboxdec.c File Reference
static int ffat_set_extradata (AVCodecContext *avctx) static av_cold int ffat_create_decoder (AVCodecContext *avctx, AVPacket *pkt) ...
包含的文件是audiotool 找对应的库，马上可以解决问题