編譯FFmpeg過程中遇到如下報錯：
1號坑：error: 'ERROR_NOT_ENOUGH_MEMORY' undeclared
libavformat/options.c:77:5: warning: 'av_oformat_next' is deprecated [-Wdeprecated-declarations]
while (ofmt = av_oformat_next(ofmt))
^~~~~
In file included from libavformat/options.c:20:0:
libavformat/avformat.h:2095:17: note: declared here
AVOutputFormat *av_oformat_next(const AVOutputFormat *f);
^~~~~~~~~~~~~~~
CC libavformat/os_support.o
In file included from libavformat/os_support.h:115:0,
from libavformat/os_support.c:29:
libavformat/os_support.c: In function 'ff_gai_strerror':
libavformat/os_support.c:194:10: error: 'ERROR_NOT_ENOUGH_MEMORY' undeclared (first use in this function)
case EAI_MEMORY:
^
libavformat/os_support.c:194:10: note: each undeclared identifier is reported only once for each function it appears in
make: *** [libavformat/os_support.o] Error 1
or
make: [ffbuild/.config] Error 127 (ignored)
WARNING: libavdevice/alldevices.c libavfilter/allfilters.c libavformat/allformats.c libavcodec/allcodecs.c libavcodec/bitstream_filters.c libavcodec/parsers.c libavformat/protocols.c newer than config.h, rerun configure
make: [ffbuild/.config] Error 127 (ignored)
CC libavformat/os_support.o
In file included from libavformat/os_support.h:115:0,
from libavformat/os_support.c:29:
libavformat/os_support.c: In function 'ff_gai_strerror':
libavformat/os_support.c:194:10: error: 'ERROR_NOT_ENOUGH_MEMORY' undeclared (first use in this function)
case EAI_MEMORY:
^
libavformat/os_support.c:194:10: note: each undeclared identifier is reported only once for each function it appears in
make: *** [libavformat/os_support.o] Error 1
解決：
在os_support.h中增加winerror.h頭文件的引用：
2號坑：error: 'ENOTCONN' undeclared
make: [ffbuild/.config] Error 127 (ignored)
WARNING: libavdevice/alldevices.c libavfilter/allfilters.c libavformat/allformats.c libavcodec/allcodecs.c libavcodec/bitstream_filters.c libavcodec/parsers.c libavformat/protocols.c newer than config.h, rerun configure
make: [ffbuild/.config] Error 127 (ignored)
CC libavformat/rtsp.o
libavformat/rtsp.c: In function 'rtsp_send_cmd_with_content_async':
libavformat/rtsp.c:1322:16: error: 'ENOTCONN' undeclared (first use in this function)
return ENOTCONN;
^~~~~~~~
libavformat/rtsp.c:1322:16: note: each undeclared identifier is reported only once for each function it appears in
解決：
可以配置引用宏 ENOTCONN 的頭文件，因爲 ENOTCONN 其實對應着126這個值，最簡單的做法就是直接修改爲126。
3號坑：ffmpeg 由於找不到libiconv-2.dll 無法繼續執行代碼。重新安裝程序可能會解決此問題。
運行編譯出來的ffmpeg.exe文件，報錯：
原本以爲自己編譯的ffmpeg.exe必須依賴libiconv-2.dll庫，就把libiconv-2.dll拷貝到同級目錄，再運行依然報錯：
看來是自己想簡單了！
搜遍了網絡資源也沒有找到解決辦法，自己就經過兩個小時的嘗試，終於找到了解決方法。
一、 拷貝libiconv-2.dll庫到msys.bat腳本依賴的bin目錄下，如圖：
二、運行如下命令註冊libiconv-2.dll庫到系統中。
regsvr32 libiconv-2.dll /s
如果沒有報錯，表示註冊成功。
三、configure配置項增加“--disable-iconv”。
完成上述三步，再運行./configure && make 進行編譯。
終於，這次編譯出來的ffmpeg.exe可以正常使用了。
趕緊使用如下命令測試一下：
./ffmpeg.exe -h
如果ffmpeg.exe正常可用，會得到如下結果：
$ ./ffmpeg.exe -h
ffmpeg version n4.2.2-9-g393eff8 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 6.3.0 (MinGW.org GCC-6.3.0-1)
configuration: --disable-everything --disable-x86asm --enable-encoder=aac --disable-iconv
libavutil 56. 31.100 / 56. 31.100
libavcodec 58. 54.100 / 58. 54.100
libavformat 58. 29.100 / 58. 29.100
libavdevice 58. 8.100 / 58. 8.100
libavfilter 7. 57.100 / 7. 57.100
libswscale 5. 5.100 / 5. 5.100
libswresample 3. 5.100 / 3. 5.100
Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...
Getting help:
-h -- print basic options
-h long -- print more options
-h full -- print all options (including all format and codec specific options, very long)
-h type=name -- print all options for the named decoder/encoder/demuxer/muxer/filter/bsf
See man ffmpeg for detailed description of the options.
Print help / information / capabilities:
-L show license
-h topic show help
-? topic show help
-help topic show help
--help topic show help
-version show version
-buildconf show build configuration
-formats show available formats
-muxers show available muxers
-demuxers show available demuxers
-devices show available devices
-codecs show available codecs
-decoders show available decoders
-encoders show available encoders
-bsfs show available bit stream filters
-protocols show available protocols
-filters show available filters
-pix_fmts show available pixel formats
-layouts show standard channel layouts
-sample_fmts show available audio sample formats
-colors show available color names
-sources device list sources of the input device
-sinks device list sinks of the output device
-hwaccels show available HW acceleration methods
Global options (affect whole program instead of just one file:
-loglevel loglevel set logging level
-v loglevel set logging level
-report generate a report
-max_alloc bytes set maximum size of a single allocated block
-y overwrite output files
-n never overwrite output files
-ignore_unknown Ignore unknown stream types
-filter_threads number of non-complex filter threads
-filter_complex_threads number of threads for -filter_complex
-stats print progress report during encoding
-max_error_rate maximum error rate ratio of errors (0.0: no errors, 1.0: 100% errors) above which ffmpeg returns an error instead of success.
-bits_per_raw_sample number set the number of bits per raw sample
-vol volume change audio volume (256=normal)
Per-file main options:
-f fmt force format
-c codec codec name
-codec codec codec name
-pre preset preset name
-map_metadata outfile[,metadata]:infile[,metadata] set metadata information of outfile from infile
-t duration record or transcode "duration" seconds of audio/video
-to time_stop record or transcode stop time
-fs limit_size set the limit file size in bytes
-ss time_off set the start time offset
-sseof time_off set the start time offset relative to EOF
-seek_timestamp enable/disable seeking by timestamp with -ss
-timestamp time set the recording timestamp ('now' to set the current time)
-metadata string=string add metadata
-program title=string:st=number... add program with specified streams
-target type specify target file type ("vcd", "svcd", "dvd", "dv" or "dv50" with optional prefixes "pal-", "ntsc-" or "film-")
-apad audio pad
-frames number set the number of frames to output
-filter filter_graph set stream filtergraph
-filter_script filename read stream filtergraph description from a file
-reinit_filter reinit filtergraph on input parameter changes
-discard discard
-disposition disposition
Video options:
-vframes number set the number of video frames to output
-r rate set frame rate (Hz value, fraction or abbreviation)
-s size set frame size (WxH or abbreviation)
-aspect aspect set aspect ratio (4:3, 16:9 or 1.3333, 1.7777)
-bits_per_raw_sample number set the number of bits per raw sample
-vn disable video
-vcodec codec force video codec ('copy' to copy stream)
-timecode hh:mm:ss[:;.]ff set initial TimeCode value.
-pass n select the pass number (1 to 3)
-vf filter_graph set video filters
-ab bitrate audio bitrate (please use -b:a)
-b bitrate video bitrate (please use -b:v)
-dn disable data
Audio options:
-aframes number set the number of audio frames to output
-aq quality set audio quality (codec-specific)
-ar rate set audio sampling rate (in Hz)
-ac channels set number of audio channels
-an disable audio
-acodec codec force audio codec ('copy' to copy stream)
-vol volume change audio volume (256=normal)
-af filter_graph set audio filters
Subtitle options:
-s size set frame size (WxH or abbreviation)
-sn disable subtitle
-scodec codec force subtitle codec ('copy' to copy stream)
-stag fourcc/tag force subtitle tag/fourcc
-fix_sub_duration fix subtitles duration
-canvas_size size set canvas size (WxH or abbreviation)
-spre preset set the subtitle options to the indicated preset
至此，終於把FFmpeg最新的4.2.2版本在windows上編譯過了。不容易，windows系統坑太多。相比較macOS，複雜繁瑣了不少。
上邊的幾個問題，是編譯過程中比較容易遇到的，希望對你有所幫助！