【iOS】Xcode 12打包IJKMediaFramework.framework遇到的问题

问题前提：
新公司项目用到 ijkplayer 进行直播业务的播放，接手项目后有个业务需求对拉流延迟要求比较高，经过一系列 debug 后发现 iOS 端 ijkplayer 延迟略大于 Android 端，于是决定对 ijkplayer 的高延迟问题进行调优

前面的准备工作在这里不做赘述，在编译 ffmpeg 时（执行./compile-ffmpeg.sh all）时会有报错，如下：

./libavutil/arm/asm.S:44:9: error: unknown directive
        .arch armv7-a
        ^
./libavutil/arm/asm.S:57:9: error: unknown directive
        .fpu neon
        ^
make: *** [libavcodec/arm/aacpsdsp_neon.o] Error 1
make: *** Waiting for unfinished jobs....

ijkplayer 的编译、打包 framework 和 https 支持这篇文章中讲述最新的 Xcode 生成二进制包所支持的指令集排除了armv7，并提供了解决方案，大家可以参考，我尝试了一下确实可行。

鉴于我们项目目前支持的指令集包括armv7，所以我尝试了其他方法解决这个错误，我尝试了旧版 Xcode 尝试无果（最新的 macOS 也不支持下载过老的 Xcode 版本）。最后找到如下的解决方案：
在/iOS/tools/do-compile-ffmpeg.sh中

将
FFMPEG_CFG_FLAGS="$FFMPEG_CFG_FLAGS $FFMPEG_CFG_FLAGS_ARM"
修改为
FFMPEG_CFG_FLAGS="$FFMPEG_CFG_FLAGS --enable-pic --disable-asm"

然后重新执行

./compile-ffmpeg.sh all

这样我们再打开IJKMediaDemo项目就可以运行起来了

其他问题

问题1：
运行IJKMediaDemo报错如下：

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_IJKFFOptions", referenced from:
      objc-class-ref in IJKMoviePlayerViewController.o
  "_OBJC_CLASS_$_IJKFFMoviePlayerController", referenced from:
      objc-class-ref in IJKMoviePlayerViewController.o
  "_IJKMPMoviePlayerLoadStateDidChangeNotification", referenced from:
      -[IJKVideoViewController installMovieNotificationObservers] in IJKMoviePlayerViewController.o
      -[IJKVideoViewController removeMovieNotificationObservers] in IJKMoviePlayerViewController.o
  "_IJKMPMoviePlayerPlaybackDidFinishReasonUserInfoKey", referenced from:
      -[IJKVideoViewController moviePlayBackDidFinish:] in IJKMoviePlayerViewController.o
  "_IJKMPMoviePlayerPlaybackDidFinishNotification", referenced from:
      -[IJKVideoViewController installMovieNotificationObservers] in IJKMoviePlayerViewController.o
      -[IJKVideoViewController removeMovieNotificationObservers] in IJKMoviePlayerViewController.o
  "_IJKMPMediaPlaybackIsPreparedToPlayDidChangeNotification", referenced from:
      -[IJKVideoViewController installMovieNotificationObservers] in IJKMoviePlayerViewController.o
      -[IJKVideoViewController removeMovieNotificationObservers] in IJKMoviePlayerViewController.o
  "_IJKMPMoviePlayerPlaybackStateDidChangeNotification", referenced from:
      -[IJKVideoViewController installMovieNotificationObservers] in IJKMoviePlayerViewController.o
      -[IJKVideoViewController removeMovieNotificationObservers] in IJKMoviePlayerViewController.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

解决办法：
Build Phases - Link Binary With Libraries - "+"，添加IJKMediaFramework.framework，再次运行就可以运行成功了（模拟器运行即可）

问题2：通过如下命令进行真机和模拟器framework合并时：

lipo -create Release-iphoneos/IJKMediaFramework.framework/IJKMediaFramework Release-iphonesimulator/IJKMediaFramework.framework/IJKMediaFramework -output IJKMediaFramework

输出如下错误：

fatal error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/lipo: Release-iphoneos/IJKMediaFramework.framework/IJKMediaFramework and Release-iphonesimulator/IJKMediaFramework.framework/IJKMediaFramework have the same architectures (arm64) and can't be in the same fat output file

这是因为Xcode 12 之前编译模拟器静态库支持i386和x86_64架构，Xcode 12 之后也支持arm64架构，而编译真机静态库支持arm64和armv7架构，所以导致合并时有冲突
解决办法：
用Xcode 11编译静态库后进行合并

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未完待续...