FFmpeg tutorial on Mac OS X - tutorial01

之前已試過在 Linux 的平台上練習 FFmpeg tutorial (見 FFmpeg tutorial practice - tutorial01)，接著我想在 Mac OS X 上也做一樣的事。理論上，需要修改的地方應該不多，只是細節要怎麼處理就需要花一點時間試。當我把程式碼從 Linux 平台上放到 Mac OS 的平台上時，一樣先從 tutorial01 開始；當然，我們需要 Mac 版的 FFmpeg，所以需要在 Mac OS 平台上編譯出它的函式庫來用。我算是 Mac OS 平台上的新手，大約一年多的使用經驗，在 Linux 平台上知道怎麼做的事，到 Mac OS 平台上卻不一定知道怎麼處理。不過沒關係，花點時間找一下就可以了。

首先我遇到的是新增函式庫的問題，我使用的 Linux 平台是 Ubuntu，如果少了某某函式庫，可以用很多方式去安裝新的函式庫，Ubuntu 的軟體中心（Ubuntu Software Center）也做的不錯，可以很容易管理你的軟體安裝結果；但在 Mac OS 平台上，是用不同的方式做的，目前我用的是 MacPorts 來管理，因為在編譯 FFmpeg 時，遇到有缺少函式庫的問題，所以我用了 MacPorts 去新增了需要的函式庫。（MacPorts 的使用方法，在這裡就不說了，利用 Google 可以找到很多的說明。）


在編譯完 FFmpeg 之後，接著就是要編譯 tutorial01。直接拿之前在 Linux 平台上編譯過的程式碼來用，當然，一定會有問題的！

ld: library not found for -lrt
collect2: ld returned 1 exit status
make: *** [tutorial01] Error 1

找不找 rt 這個函式庫，那就先把它移除吧！

Undefined symbols for architecture x86_64:
 "_BZ2_bzDecompress", referenced from:
     _matroska_decode_buffer in libavformat.a(matroskadec.o)
 "_BZ2_bzDecompressEnd", referenced from:
     _matroska_decode_buffer in libavformat.a(matroskadec.o)
 "_BZ2_bzDecompressInit", referenced from:
     _matroska_decode_buffer in libavformat.a(matroskadec.o)
 "_CFDataCreate", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_CFDictionaryCreate", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
 "_CFDictionaryCreateMutable", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_CFDictionaryGetValue", referenced from:
     _vda_decoder_callback in libavcodec.a(vda_h264.o)
 "_CFDictionarySetValue", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_CFNumberCreate", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_CFNumberGetValue", referenced from:
     _vda_decoder_callback in libavcodec.a(vda_h264.o)
 "_CFRelease", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_CVPixelBufferGetBaseAddress", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferGetBaseAddressOfPlane", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferGetBytesPerRow", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferGetBytesPerRowOfPlane", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferGetPixelFormatType", referenced from:
     _vda_decoder_callback in libavcodec.a(vda_h264.o)
 "_CVPixelBufferGetPlaneCount", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferIsPlanar", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferLockBaseAddress", referenced from:
     _vdadec_decode in libavcodec.a(vda_h264_dec.o)
 "_CVPixelBufferRelease", referenced from:
     _release_buffer in libavcodec.a(vda_h264_dec.o)
     _ff_vda_release_vda_frame in libavcodec.a(vda_h264.o)
     _ff_vda_destroy_decoder in libavcodec.a(vda_h264.o)
 "_CVPixelBufferRetain", referenced from:
     _vda_decoder_callback in libavcodec.a(vda_h264.o)
 "_CVPixelBufferUnlockBaseAddress", referenced from:
     _release_buffer in libavcodec.a(vda_h264_dec.o)
 "_VDADecoderCreate", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_VDADecoderDecode", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
 "_VDADecoderDestroy", referenced from:
     _ff_vda_destroy_decoder in libavcodec.a(vda_h264.o)
 "_VDADecoderFlush", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
 "___CFConstantStringClassReference", referenced from:
     CFString in libavcodec.a(vda_h264.o)
 "_kCFAllocatorDefault", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kCFCoreFoundationVersionNumber", referenced from:
     _vdadec_init in libavcodec.a(vda_h264_dec.o)
 "_kCFTypeDictionaryKeyCallBacks", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kCFTypeDictionaryValueCallBacks", referenced from:
     _end_frame in libavcodec.a(vda_h264.o)
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kCVPixelBufferIOSurfacePropertiesKey", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kCVPixelBufferPixelFormatTypeKey", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kVDADecoderConfiguration_Height", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kVDADecoderConfiguration_SourceFormat", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kVDADecoderConfiguration_Width", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
 "_kVDADecoderConfiguration_avcCData", referenced from:
     _ff_vda_create_decoder in libavcodec.a(vda_h264.o)
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [tutorial01] Error 1

接著，又出現了找不到 symbol 的訊息。我了解是少了函式庫的關係，但是哪幾個函式庫需要加呢？原來是需要加上下面幾個函式庫

-lbz2 -framework CoreFoundation 
-framework CoreVideo -framework VideoDecodeAcceleration

這些問題排除之後，tutorial01 就可以正常地編譯了！