1 获取源代码

git clone -b "branch" https://git.ffmpeg.org/ffmpeg.git

“branch” 可以是以下的master、release/3.1等等，具体看需要使用哪个分支。

5 hours ago	master	shortlog | log | tree
4 days ago	release/3.1	shortlog | log | tree
4 days ago	release/3.2	shortlog | log | tree
4 days ago	release/3.3	shortlog | log | tree
3 weeks ago	release/3.0	shortlog | log | tree
2 months ago	release/2.8	shortlog | log | tree
12 months ago	release/2.7	shortlog | log | tree
12 months ago	release/2.6	shortlog | log | tree
12 months ago	release/2.5	shortlog | log | tree

2 Configure配置

在源码的目录下调用configure脚本，通过 -h 查看相应的帮助，这里写了一个简单的脚本build-ffmpeg.sh；

#!/bin/bash

PREFIX=out
TOOLCHAINS=/mnt/diska/X3399/source/buildroot/output/host/opt/ext-toolchain/bin
CROSS_COMPILE=${TOOLCHAINS}/aarch64-linux-gnu-
LOCAL_PATH=`pwd`
CFLAGS="-Wall -pipe -fpic \
   -finline-limit=300 -ffast-math \
   -fstrict-aliasing -Werror=strict-aliasing \
   -fmodulo-sched -fmodulo-sched-allow-regmoves \
   -Wno-psabi -Wa,--noexecstack"
EXTRA_CFLAGS=
EXTRA_LDFLAGS=
CPU_NAME=cortex-a72
FFMPEG_FLAGS="--prefix=${PREFIX} \
   --target-os=linux \
   --arch=arm \
   --cpu=$CPU_NAME \
   --enable-cross-compile \
   --cross-prefix=${CROSS_COMPILE} \
   --enable-shared \
   --disable-symver \
   --disable-doc \
   --disable-ffplay \
   --disable-ffmpeg \
   --disable-ffprobe \
   --disable-ffserver \
   --disable-avdevice \
   --disable-avfilter \
   --disable-muxers \
   --disable-filters \
   --disable-devices \
   --disable-everything \
   --enable-protocols  \
   --enable-parsers \
   --enable-demuxers \
   --disable-demuxer=sbg \
   --enable-decoders \
   --enable-bsfs \
   --enable-network \
   --enable-swscale  \
   --enable-neon \
   --enable-version3 \
   --disable-yasm \
   --disable-asm"

 #--enable-debug \
 #--disable-stripping \
 #--disable-optimizations \

 ./configure $FFMPEG_FLAGS --extra-cflags="$CFLAGS $EXTRA_CFLAGS" --extra-ldflags="$LDFLAGS $EXTRA_LDFLAGS"

 #make && make install

3 报错处理

如果在根目录下直接执行build-ffmpeg.sh脚本是无法成功安装ffmpeg的，首先这里会出现以下几个问题。

报错1:

错误内容：

{your path to toolchians}/aarch64-linux-gnu-gcc is unable to create an executable file. C compiler test failed.

解决方案：

1. 打开configure文件；

2. 搜索报错内容“C compiler test failed”，定位到以下内容，注释掉 die “C compiler test failed.” 或者修改 if 条件使得条件一直成立也是可以的。

   if test "$?" != 0; then
   echo "$cc is unable to create an executable file."
   if test -z "$cross_prefix" && ! enabled cross_compile ; then
       echo "If $cc is a cross-compiler, use the --enable-cross-compile option."
       echo "Only do this if you know what cross compiling means."
   fi
   
   #   die "C compiler test failed."
   
   fi  

报错2

错误内容：

If you think configure made a mistake, make sure you are using the latest
version from Git. If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
Include the log file “config.log” produced by configure as this will help
solve the problem.

解决方案：

和报错1的解决方案类似，需要定位configure文件中的错误信息提示内容，

 die(){
     echolog "$@"
     cat <<EOF

 If you think configure made a mistake, make sure you are using the latest
 version from Git.  If the latest version fails, report the problem to the
 ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
 EOF
     if disabled logging; then
         cat <<EOF
 Rerun configure with logging enabled (do not use --disable-logging), and
 include the log this produces with your report.
 EOF
     else
         cat <<EOF
 Include the log file "$logfile" produced by configure as this will help
 solve the problem.
 EOF
     fi
 #    exit 1
 }

简单粗暴一点将exit 1直接注释掉，这样就不会退出了，但是会遇到什么问题不得而知，至少目前可以成功安装了。

报错3

错误内容：

aarch64-linux-gnu-gcc: error: missing argument to ‘-mcpu=’

解决方案：

configure 参数中加入 –cpu=$CPU_NAME 选项

4 At last

最后将out文件夹下的 文件copy到目标板上即可