Mac OS X下编译并搭建ffmpeg开发环境及常见错误处理

首先官网下载源码文件：http://www.ffmpegmac.net/，注意点击“Download Now!"字样下面的“sourcecode”进行下载。下载后是一个.7z的压缩包，可以下载“The Unarchiver”程序进行解压，上传到资源栏里了，http://download.csdn.net/detail/enter_/9629936

这里有官网的编译方法：https://trac.ffmpeg.org/wiki/CompilationGuide/MacOSX。

首先最好是先把xcode装上，然后安装Homebrew ，它类似Ubuntu下面的 apt-get ，用习惯了apt-get 然后切换到mac下没有这样一个工具是一件很苦恼的事情，所以Homebrew就是apt-get一样好用。直接复制下面的代码到终端就好，这里不需要sudo，安装完使用的时候也不需要sudo。

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

下面就是brew的使用方法了，同样的，直接复制下面的代码到终端就好。

brew install automake fdk-aac git lame libass libtool libvorbis libvpx \
opus sdl shtool texi2html theora wget x264 xvid yasm

在下载安装这些工具的时候可能会出很多问题。如果出现类似 /usr/local/share/man/man1 : Permission denied 的错误，那应该是该目录下没有创建该目录，或者该目录没有写权限，解决办法是到该目录下mkdir对应的目录，然后修改权限为777，如：

$sudo mkdir /usr/local/share/man/man1

$sudo chmod 777 /usr/local/share/man/man1

然后是配置configure，首先应该进入到解压后的ffmpeg目录下，然后在执行configure之前先在解压的ffmpeg目录下执行，直接复制到终端即可：

CFLAGS=`freetype-config --cflags` LDFLAGS=`freetype-config --libs` PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig:/usr/lib/pkgconfig:/usr/X11/lib/pkgconfig 

然后再执行configure，

./configure  --prefix=/usr/local --enable-gpl --enable-nonfree --enable-libass \
--enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus \
--enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --extra-ldflags=-L/usr/local/lib

注意上面命令最后的参数：--extra-ldflags=-L/usr/local/lib，这个是用于找到相应的库的，如上面的yasm等，这些命令在安装并完成link后一般都会出现在/usr/local/lib目录下，所以这里直接添加库目录进去。

如果碰到类似的错误: ERROR: xxx not found，yasm/nasm not found or too old. Use --disable-yasm for a crippled build. 或者：yasm-1.3.0 already installed, it's just not linked。编译ffmpeg会用到汇编用于加速。解决办法：

首先，在终端上:$brew install xxx，如这里可以$brew install yasm，安装相应的命令。

如果提示xxx已经安装只是just not linked。那么直接用brew连接就好：$brew link xxx，如这里可以：$brew link yasm。链接后会在/usr/local/lib下生成一个链接文件指向相应的库。

configure这步没有问题后就可以往下执行了，都是些老套路，和Linux下一样一样的。

$make

$sudo make install

这里顺便说下添加环境变量的做法，一般常规是这样：export PATH=$PATH:/xxx/xx/bin，但是这样做只会对当前的终端生效，想要永久生效的话可以直接在bash文件中添加配置，做法如下：

$vim ~/.bash_profile

然后在打开的bash_profile中添加：export PATH=$PATH:/xxx/xxx/bin

保存后退出重启电脑即可生效。以后添加配置或者环境变量的时候都可以直接添加在这个文件里面。

最后是编译好的ffmpeg的include、lib、bin。需要的可以直接下载，版本为3.1.3。

如果编译上还有问题的可以直接留言探讨。

然后是搭建ffmpeg的运行环境了，这个就比较简单了，在这里简单说说QT和自己写Makefile时的几个问题。

首先放个测试用例，这里会输出ffmpeg的配置信息：（文件名为main.cpp）

#include <stdio.h>

extern "C"
{
#include "libavcodec/avcodec.h"
}

int main()
{
    printf("%s\n", avcodec_configuration());
    return 0;
}

运行后输出结果如下：

--prefix=/usr/local --enable-gpl --enable-nonfree --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --extra-ldflags=-L/usr/local/lib

Qt下要记得加入编译好的ffmpeg静态库，可以全给它加上去，需添加的配置如下：

QMAKE_MACOSX_DEPLOYMENT_TARGET = 10.11

LIBS += "/usr/local/lib/libavcodec.a" \
        "/usr/local/lib/libavdevice.a" \
        "/usr/local/lib/libavfilter.a" \
        "/usr/local/lib/libavformat.a" \
        "/usr/local/lib/libavutil.a" \
        "/usr/local/lib/libpostproc.a" \
        "/usr/local/lib/libswresample.a" \
        "/usr/local/lib/libswscale.a"
LIBS += -liconv

SOURCES += main.cpp

INCLUDEPATH += "/usr/local/include"

如果是自己写Makefile的话，就是：（下面可以是clang或者g++）

clang -I /usr/local/include -o main main.cpp /usr/local/lib/libavcodec.a /usr/local/lib/libavutil.a  -liconv

如果在编译测试用例的时候出现下面这样的问题：

error: symbol(s) not found for architecture x86_64
error: linker command failed with exit code 1 (use -v to see invocation)

那主要的原因还是库没有链接完整，第一个检查ffmpeg用到的库链接到了没有，如上面不能只写libavcodec.a，少了libavutil.a就有这样的问题。

然后就是是否忘了链接iconv库，因为ffmpeg库中用到了iconv库的。

还有就是如果你是在c++中使用ffmpeg，那么不能忘了上面加入头文件时的 extern “C"{}，不然也会出现上面那个错误。

比如我第一次运行的时候就是上面有些库没有链接到，出现了下面这些信息，害我查了很久，错误信息如下：

Undefined symbols for architecture x86_64:
  "_av_bprint_clear", referenced from:
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
  "_av_bprint_finalize", referenced from:
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
      _avpriv_bprint_to_extradata in libavcodec.a(utils.o)
  "_av_bprint_init", referenced from:
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
  "_av_bprintf", referenced from:
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
  "_av_buffer_alloc", referenced from:
      _av_grow_packet in libavcodec.a(avpacket.o)
      _av_packet_merge_side_data in libavcodec.a(avpacket.o)
      _ff_thread_get_buffer in libavcodec.a(pthread_frame.o)
  "_av_buffer_allocz", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_av_buffer_create", referenced from:
      _av_packet_from_data in libavcodec.a(avpacket.o)
  "_av_buffer_default_free", referenced from:
      _av_packet_from_data in libavcodec.a(avpacket.o)
  "_av_buffer_pool_get", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_av_buffer_pool_init", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_av_buffer_pool_uninit", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _avcodec_close in libavcodec.a(utils.o)
  "_av_buffer_realloc", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _avcodec_encode_video2 in libavcodec.a(utils.o)
      _av_new_packet in libavcodec.a(avpacket.o)
      _av_grow_packet in libavcodec.a(avpacket.o)
      _copy_packet_data in libavcodec.a(avpacket.o)
      _av_packet_ref in libavcodec.a(avpacket.o)
  "_av_buffer_ref", referenced from:
      _ff_thread_ref_frame in libavcodec.a(utils.o)
      _copy_packet_data in libavcodec.a(avpacket.o)
      _av_packet_ref in libavcodec.a(avpacket.o)
      _avcodec_copy_context in libavcodec.a(options.o)
  "_av_buffer_unref", referenced from:
      _avcodec_close in libavcodec.a(utils.o)
      _av_packet_alloc in libavcodec.a(avpacket.o)
      _av_packet_unref in libavcodec.a(avpacket.o)
      _av_packet_free in libavcodec.a(avpacket.o)
      _av_copy_packet_side_data in libavcodec.a(avpacket.o)
      _copy_packet_data in libavcodec.a(avpacket.o)
      _av_free_packet in libavcodec.a(avpacket.o)
      ...
  "_av_chroma_location_name", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_color_primaries_name", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_color_range_name", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_color_space_name", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_color_transfer_name", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_cpu_count", referenced from:
      _ff_frame_thread_encoder_init in libavcodec.a(frame_thread_encoder.o)
      _ff_frame_thread_init in libavcodec.a(pthread_frame.o)
      _ff_slice_thread_init in libavcodec.a(pthread_slice.o)
  "_av_dict_copy", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _ff_frame_thread_encoder_init in libavcodec.a(frame_thread_encoder.o)
  "_av_dict_free", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _ff_frame_thread_encoder_init in libavcodec.a(frame_thread_encoder.o)
  "_av_dict_get", referenced from:
      _av_packet_pack_dictionary in libavcodec.a(avpacket.o)
      _ff_frame_thread_encoder_init in libavcodec.a(frame_thread_encoder.o)
  "_av_dict_set", referenced from:
      _av_packet_unpack_dictionary in libavcodec.a(avpacket.o)
      _ff_frame_thread_encoder_init in libavcodec.a(frame_thread_encoder.o)
  "_av_fast_realloc", referenced from:
      _ff_thread_release_buffer in libavcodec.a(pthread_frame.o)
  "_av_fifo_alloc_array", referenced from:
      _ff_frame_thread_encoder_init in libavcodec.a(frame_thread_encoder.o)
  "_av_fifo_freep", referenced from:
      _ff_frame_thread_encoder_free in libavcodec.a(frame_thread_encoder.o)
  "_av_fifo_generic_read", referenced from:
      _worker in libavcodec.a(frame_thread_encoder.o)
  "_av_fifo_generic_write", referenced from:
      _ff_thread_video_encode_frame in libavcodec.a(frame_thread_encoder.o)
  "_av_fifo_size", referenced from:
      _worker in libavcodec.a(frame_thread_encoder.o)
  "_av_frame_alloc", referenced from:
      _ff_reget_buffer in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _ff_thread_video_encode_frame in libavcodec.a(frame_thread_encoder.o)
      _ff_frame_thread_init in libavcodec.a(pthread_frame.o)
      _ff_snow_common_init in libavcodec.a(snow.o)
  "_av_frame_copy", referenced from:
      _ff_reget_buffer in libavcodec.a(utils.o)
  "_av_frame_copy_props", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _unrefcount_frame in libavcodec.a(utils.o)
  "_av_frame_free", referenced from:
      _ff_reget_buffer in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _avcodec_close in libavcodec.a(utils.o)
      _worker in libavcodec.a(frame_thread_encoder.o)
      _ff_thread_video_encode_frame in libavcodec.a(frame_thread_encoder.o)
      _ff_frame_thread_free in libavcodec.a(pthread_frame.o)
      ...
  "_av_frame_get_buffer", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
  "_av_frame_get_channels", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _unrefcount_frame in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_frame_get_color_range", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
  "_av_frame_get_colorspace", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
  "_av_frame_get_pkt_duration", referenced from:
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_frame_get_side_data", referenced from:
      _ff_side_data_update_matrix_encoding in libavcodec.a(utils.o)
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _ff_alloc_a53_sei in libavcodec.a(utils.o)
  "_av_frame_is_writable", referenced from:
      _ff_reget_buffer in libavcodec.a(utils.o)
  "_av_frame_move_ref", referenced from:
      _ff_reget_buffer in libavcodec.a(utils.o)
      _unrefcount_frame in libavcodec.a(utils.o)
      _avcodec_receive_frame in libavcodec.a(utils.o)
      _ff_thread_decode_frame in libavcodec.a(pthread_frame.o)
      _ff_thread_release_buffer in libavcodec.a(pthread_frame.o)
  "_av_frame_new_side_data", referenced from:
      _ff_side_data_update_matrix_encoding in libavcodec.a(utils.o)
      _ff_init_buffer_info in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_frame_ref", referenced from:
      _ff_thread_ref_frame in libavcodec.a(utils.o)
      _ff_thread_video_encode_frame in libavcodec.a(frame_thread_encoder.o)
  "_av_frame_set_best_effort_timestamp", referenced from:
      _avcodec_decode_video2 in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_frame_set_channels", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _unrefcount_frame in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_frame_set_color_range", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
  "_av_frame_set_colorspace", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
  "_av_frame_set_pkt_duration", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_frame_set_pkt_pos", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
      _avcodec_decode_video2 in libavcodec.a(utils.o)
  "_av_frame_set_pkt_size", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
  "_av_frame_unref", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _ff_reget_buffer in libavcodec.a(utils.o)
      _avcodec_decode_video2 in libavcodec.a(utils.o)
      _unrefcount_frame in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
      _avcodec_receive_frame in libavcodec.a(utils.o)
      _avcodec_flush_buffers in libavcodec.a(utils.o)
      ...
  "_av_free", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _avpriv_bprint_to_extradata in libavcodec.a(utils.o)
      _default_lockmgr_cb in libavcodec.a(utils.o)
      _worker in libavcodec.a(frame_thread_encoder.o)
      _avcodec_alloc_context3 in libavcodec.a(options.o)
      _ff_slice_thread_init in libavcodec.a(pthread_slice.o)
      _ff_snow_alloc_blocks in libavcodec.a(snow.o)
      ...
     (maybe you meant: _av_free_packet)
  "_av_freep", referenced from:
      _av_fast_padded_malloc in libavcodec.a(utils.o)
      _av_fast_padded_mallocz in libavcodec.a(utils.o)
      _avcodec_fill_audio_frame in libavcodec.a(utils.o)
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _ff_get_format in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
      ...
  "_av_gcd", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_get_bytes_per_sample", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_get_channel_layout_nb_channels", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
  "_av_get_channel_layout_string", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_string in libavcodec.a(utils.o)
  "_av_get_colorspace_name", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_get_cpu_flags", referenced from:
      _ff_me_cmp_init_x86 in libavcodec.a(me_cmp_init.o)
      _ff_dwt_init_x86 in libavcodec.a(snowdsp.o)
      _ff_h264qpel_init_x86 in libavcodec.a(h264_qpel.o)
      _ff_hpeldsp_init_x86 in libavcodec.a(hpeldsp_init.o)
      _ff_videodsp_init_x86 in libavcodec.a(videodsp_init.o)
  "_av_get_media_type_string", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_get_pix_fmt_name", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _ff_reget_buffer in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_string in libavcodec.a(utils.o)
  "_av_get_planar_sample_fmt", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
  "_av_get_sample_fmt_name", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_string in libavcodec.a(utils.o)
  "_av_image_check_sar", referenced from:
      _ff_set_sar in libavcodec.a(utils.o)
      _ff_init_buffer_info in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
  "_av_image_check_size", referenced from:
      _avcodec_set_dimensions in libavcodec.a(utils.o)
      _ff_set_dimensions in libavcodec.a(utils.o)
      _ff_get_buffer in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_encode_video2 in libavcodec.a(utils.o)
      _avcodec_decode_video2 in libavcodec.a(utils.o)
      _apply_param_change in libavcodec.a(utils.o)
      ...
  "_av_image_fill_linesizes", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_av_image_fill_pointers", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_av_log", referenced from:
      _av_fast_padded_malloc in libavcodec.a(utils.o)
      _av_fast_padded_mallocz in libavcodec.a(utils.o)
      _avcodec_set_dimensions in libavcodec.a(utils.o)
      _ff_set_sar in libavcodec.a(utils.o)
      _ff_color_frame in libavcodec.a(utils.o)
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _ff_init_buffer_info in libavcodec.a(utils.o)
      ...
     (maybe you meant: _av_log_ask_for_sample, _av_log_missing_feature )
  "_av_log_get_level", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_malloc", referenced from:
      _ff_get_format in libavcodec.a(utils.o)
      _unrefcount_frame in libavcodec.a(utils.o)
      _default_lockmgr_cb in libavcodec.a(utils.o)
      _av_copy_packet_side_data in libavcodec.a(avpacket.o)
      _av_packet_split_side_data in libavcodec.a(avpacket.o)
      _ff_frame_thread_init in libavcodec.a(pthread_frame.o)
      _avcodec_alloc_context3 in libavcodec.a(options.o)
      ...
  "_av_mallocz", referenced from:
      _av_fast_padded_malloc in libavcodec.a(utils.o)
      _av_fast_padded_mallocz in libavcodec.a(utils.o)
      _avcodec_fill_audio_frame in libavcodec.a(utils.o)
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _ff_get_format in libavcodec.a(utils.o)
      _avcodec_open2 in libavcodec.a(utils.o)
      _av_cpb_properties_alloc in libavcodec.a(utils.o)
      ...
  "_av_match_list", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
  "_av_mul_q", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_decode_video2 in libavcodec.a(utils.o)
  "_av_opt_copy", referenced from:
      _avcodec_copy_context in libavcodec.a(options.o)
  "_av_opt_free", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_close in libavcodec.a(utils.o)
      _ff_frame_thread_free in libavcodec.a(pthread_frame.o)
      _avcodec_copy_context in libavcodec.a(options.o)
  "_av_opt_set", referenced from:
      _init_context_defaults in libavcodec.a(options.o)
  "_av_opt_set_defaults", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _init_context_defaults in libavcodec.a(options.o)
  "_av_opt_set_defaults2", referenced from:
      _init_context_defaults in libavcodec.a(options.o)
  "_av_opt_set_dict", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
  "_av_pix_fmt_count_planes", referenced from:
      _ff_get_buffer in libavcodec.a(utils.o)
  "_av_pix_fmt_desc_get", referenced from:
      _avcodec_align_dimensions2 in libavcodec.a(utils.o)
      _avcodec_align_dimensions in libavcodec.a(utils.o)
      _ff_color_frame in libavcodec.a(utils.o)
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _ff_get_buffer in libavcodec.a(utils.o)
      _avcodec_default_get_format in libavcodec.a(utils.o)
      _ff_get_format in libavcodec.a(utils.o)
      ...
  "_av_realloc", referenced from:
      _av_packet_add_side_data in libavcodec.a(avpacket.o)
      _av_packet_new_side_data in libavcodec.a(avpacket.o)
      _av_packet_pack_dictionary in libavcodec.a(avpacket.o)
      _av_packet_copy_props in libavcodec.a(avpacket.o)
      _ff_side_data_set_encoder_stats in libavcodec.a(avpacket.o)
  "_av_realloc_array", referenced from:
      _ff_add_cpb_side_data in libavcodec.a(utils.o)
  "_av_reallocp_array", referenced from:
      _ff_thread_decode_frame in libavcodec.a(pthread_frame.o)
  "_av_reduce", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_rescale_q", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
      _av_packet_rescale_ts in libavcodec.a(avpacket.o)
  "_av_sample_fmt_is_planar", referenced from:
      _avcodec_fill_audio_frame in libavcodec.a(utils.o)
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
  "_av_samples_copy", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
      _avcodec_decode_audio4 in libavcodec.a(utils.o)
  "_av_samples_fill_arrays", referenced from:
      _avcodec_fill_audio_frame in libavcodec.a(utils.o)
  "_av_samples_get_buffer_size", referenced from:
      _avcodec_fill_audio_frame in libavcodec.a(utils.o)
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_av_samples_set_silence", referenced from:
      _avcodec_encode_audio2 in libavcodec.a(utils.o)
  "_av_strdup", referenced from:
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
  "_av_strlcat", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_strlcatf", referenced from:
      _avcodec_string in libavcodec.a(utils.o)
  "_av_vlog", referenced from:
      _av_log_ask_for_sample in libavcodec.a(utils.o)
  "_avpriv_frame_get_metadatap", referenced from:
      _ff_init_buffer_info in libavcodec.a(utils.o)
  "_avpriv_set_systematic_pal2", referenced from:
      _avcodec_default_get_buffer2 in libavcodec.a(utils.o)
  "_iconv", referenced from:
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
  "_iconv_close", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
  "_iconv_open", referenced from:
      _avcodec_open2 in libavcodec.a(utils.o)
      _avcodec_decode_subtitle2 in libavcodec.a(utils.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)