FFmpeg 开源项目分析(十)白嫖ijkplayer库

FFmpeg 开源项目分析(一)FFmpeg/Openssl/x264编译
FFmpeg 开源项目分析(二)AVFormatContext解析
FFmpeg 开源项目分析(三)AVStream解析
FFmpeg 开源项目分析(四)AVCodecParameters解析
FFmpeg 开源项目分析(五)PC上实战
FFmpeg 开源项目分析(六)FFmpeg中文件操作
FFmpeg 开源项目分析(七)解封、解码
FFmpeg 开源项目分析(八)修改视频封装格式
FFmpeg 开源项目分析(九)Android输出av_log
FFmpeg 开源项目分析(十)白嫖ijkplayer库
FFmpeg 开源项目分析(十一)FFmpeg代码架构

我们要引入ijkplayer播放器的时候，发现一个小小的缺陷就是so库太大了，一般有3个so库：

jeffmony@JeffMonydeMacBook-Pro arm64-v8a % ls -hl
total 21240
-rwxr-xr-x  1 jeffmony  staff   9.6M  4 30 00:25 libijkffmpeg.so
-rwxr-xr-x  1 jeffmony  staff   348K  4 30 00:25 libijkplayer.so
-rwxr-xr-x  1 jeffmony  staff   474K  4 30 00:25 libijksdl.so

其中一个libijkffmpeg.so库非常大，有近9.6M，这个非常吓人了，当然你可以裁剪一些不用的库。

但是ijkplayer毕竟只是播放视频才用到的。但是ijkplayer底层是基于ffmpeg的ffplay播放框架，也就是说ffmpeg也集成到了libijkffmpeg.so中了。

这就有点意思了，那我们需要引用ffmpeg中的一些方法就不用额外的编译库了，直接使用libijkffmpeg.so中的文件就可以的。

• 1.节省了空间大小，防止重复编译ffmpeg导致的包体积增大。
• 2.native接口不用和ijkplayer的上层写在一起，可以单独写，完全不影响。

看一下这个提交：
https://github.com/JeffMony/PlayerSDK/commit/af1482d1842583772702a953d4612ae50d9a5631

• 1.复用libijkffmpeg.so
• 2.引入ffmpeg头文件
• 3.编译生成新的so

1.FFmpeg头文件如何生成

具体的build_ffmpeg.sh如下：

#!/bin/bash
export NDK_ROOT=/Users/jeffmony/tools/android-ndk-r14b # 修改自己本地的ndk路径

build() {
API=24
ARCH=$1
PLATFORM=$2
SYSROOT=$NDK_ROOT/platforms/android-$API/arch-$ARCH/
CROSS_PREFIX=$NDK_ROOT/toolchains/$PLATFORM-4.9/prebuilt/darwin-x86_64/bin/$PLATFORM-
PREFIX=$(pwd)/android/$ARCH #自己指定一个输出目录
rm -rf $(pwd)/android/$ARCH

echo "开始编译ffmpeg $ARCH so"
./configure \
--prefix=$PREFIX \
--disable-doc \
--enable-shared \
--disable-static \
--disable-x86asm \
--disable-asm \
--disable-symver \
--disable-devices \
--disable-avdevice \
--enable-gpl \
--disable-ffmpeg \
--disable-ffplay \
--disable-ffprobe \
--enable-small \
--enable-cross-compile \
--cross-prefix=$CROSS_PREFIX \
--target-os=android \
--arch=$ARCH \
--sysroot=$SYSROOT
}

# build armv7a
build arm arm-linux-androideabi
make clean
make -j4
make install

echo "完成ffmpeg $ARCH 编译..."


# build armv8a
build arm64 aarch64-linux-android
make clean
make -j4
make install

echo "完成ffmpeg $ARCH 编译..."

生成的目录中./android/arm/include 就是头文件

2.如何复用libijkffmpeg.so

主要的操作步骤如下:

• 新建一个cpp文件夹，将include文件夹拷贝到cpp下面
• 新建CMakeLists.txt和jeffmony.cpp，jeffmony.cpp就是自定义的native方法
• 修改build.gradle编译

build.gradle修改如下：

CMakeLists.txt修改如下：

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

## libijkffmpeg.so
add_library(ffmpeg SHARED IMPORTED)
set_target_properties(ffmpeg PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI}/libijkffmpeg.so)

include_directories(./include)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
        jeffmony

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        jeffmony.cpp)

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
        jeffmony
        ffmpeg
        # Links the target library to the log library
        # included in the NDK.
        ${log-lib})

编译运行，生成了一个libjeffmony.so库。

具体的项目代码见：https://github.com/JeffMony/PlayerSDK

ln -s $FF_PREFIX/include $FF_PREFIX/shared/include
ln -s $FF_PREFIX/libijkffmpeg.so $FF_PREFIX/shared/lib/libijkffmpeg.so
cp $FF_PREFIX/lib/pkgconfig/*.pc $FF_PREFIX/shared/lib/pkgconfig
for f in $FF_PREFIX/lib/pkgconfig/*.pc; do
    # in case empty dir
    if [ ! -f $f ]; then
        continue
    fi
    cp $f $FF_PREFIX/shared/lib/pkgconfig
    f=$FF_PREFIX/shared/lib/pkgconfig/`basename $f`
    # OSX sed doesn't have in-place(-i)
    mysedi $f 's/\/output/\/output\/shared/g'
    mysedi $f 's/-lavcodec/-lijkffmpeg/g'
    mysedi $f 's/-lavfilter/-lijkffmpeg/g'
    mysedi $f 's/-lavformat/-lijkffmpeg/g'
    mysedi $f 's/-lavutil/-lijkffmpeg/g'
    mysedi $f 's/-lswresample/-lijkffmpeg/g'
    mysedi $f 's/-lswscale/-lijkffmpeg/g'
done

阿的萨

• 音视频开发中使用ffmpeg的地方非常多, 播放场景/音视频编辑场景, 其中使用到ffmpeg核心模块是共通的, 本文的介绍就是告诉大家, 我们可以将不同的功能模块封在同一个ffmpeg库中, 帮我们节省空间