编译LAME
在windows中ndk-build来进行编译
1. 将libmp3lame和include中的文件拷贝到jni目录下
2. 将所有的.c文件，添加到Android.mk中的LOCAL_SRC_FILES中
注意要保存好头文件 + lib文件
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES = ./bitstream.c ./encoder.c ./fft.c ./gain_analysis.c ./id3tag.c ./lame.c ./mpglib_interface.c ./newmdct.c ./presets.c ./psymodel.c ./quantize.c ./quantize_pvt.c ./reservoir.c ./set_get.c ./tables.c ./takehiro.c ./util.c ./vbrquantize.c ./VbrTag.c ./vector/xmm_quantize_sub.c ./version.c
LOCAL_LDLIBS := -L$(SYSROOT)/usr/lib -llog
LOCAL_MODULE := liblame
include $(BUILD_SHARED_LIBRARY)
在linux中用ndk-build来编译
ndk-build配置
先下载ndk-build：https://developer.android.com/ndk/downloads/index.html
1. 初始化交叉编译工具链
（1）得到x86架构的Android Q的ndk-build交叉编译工具链，并放在my-toolchain目录中
$NDK/build/tools/make_standalone_toolchain.py \
--arch x86 \
--api 29 \
--install-dir=my-toolchain
（2）设置环境变量
# Add the standalone toolchain to the search path.
export PATH=/home/jetson/Documents/android-ndk-r22-linux-x86_64/android-ndk-r22/my-toolchain/bin:$PATH
# Tell configure what tools to use.
target_host=i686-linux-android
export AR=$target_host-ar
export AS=$target_host-clang
export CC=$target_host-clang
export CXX=$target_host-clang++
export LD=$target_host-ld
export STRIP=$target_host-strip
# Tell configure what flags Android requires.
export CFLAGS="-fPIE -fPIC"
export LDFLAGS="-pie"
进行LAME的编译
（1）配置
--host为目标编译器的前缀，--disable-shared编译为静态库
./configure --disable-shared --disable-frontend --prefix="/home/jetson/Documents/lame-3.100/thin/x86" --host=i686-linux-android
（2）编译
make -j8
最后得到libmp3lame/.libs/libmp3lame.a文件
编译ffmpeg
在linux中编译使用的
编译准备
1. 安装包：
sudo apt-get install libx11-dev
sudo apt-get install xorg-dev
sudo apt-get install yasm ： 用来提高ffmpeg的编译速度的
2. 编译安装SDL
https://www.libsdl.org/download-2.0.php
./configure
make
sudo make install
编译完SDL之后，发现使用ffplay命令是没有办法播放音乐的：
SDL_OpenAudio (2 channels, 44100 Hz): No such audio device
SDL_OpenAudio (1 channels, 44100 Hz): No such audio device
No more combinations to try, audio open failed
解决办法：
sudo apt-get install libasound2-dev
sudo apt-get install libpulse-dev
然后重新进行安装：
sudo make uninstall
sudo make distclean
./configure
sudo make
sudo make install
参考链接：https://www.codenong.com/cs106393555/
进行ffmpeg编译
1. 安装x264库
./configure --enable-shared --enable-static --prefix="/home/jetson/Documents/x264-master/x264_install" && make -j7 && make install
2. 安装fdk-aac库
./configure --enable-shared --enable-static --prefix="/home/jetson/Documents/fdk-aac-2.0.1/fdk_install" && make -j7 && make install
3. 安装lame
./configure --enable-shared --enable-static --prefix="/home/jetson/Documents/lame-3.100/lame_install" && make -j7 && make install
4. 编译安装ffmpeg
export PKG_CONFIG_PATH=/home/jetson/Documents/ffmpeg-snapshot/ffmpeg/external-libs/fdk_install/lib/pkgconfig:$PKG_CONFIG_PATH
export PKG_CONFIG_PATH=/home/jetson/Documents/ffmpeg-snapshot/ffmpeg/external-libs/x264_install/lib/pkgconfig:$PKG_CONFIG_PATH
./configure --enable-shared --enable-static --enable-libx264 --enable-gpl --enable-libfdk-aac --enable-libmp3lame --extra-cflags="-Iexternal-libs/fdk_install/include -Iexternal-libs/lame_install/include -Iexternal-libs/x264_install/include" --extra-ldflags="-Lexternal-libs/fdk_install/lib -Lexternal-libs/lame_install/lib -Lexternal-libs/x264_install/lib" --enable-nonfree --enable-avdevice
make
sudo make install
问题：
ffmpeg: error while loading shared libraries: libfdk-aac.so.2: cannot open shared object file: No such file or directory
只要sudo make install就可以了，不需要上面的external-libs了
sudo vi /etc/ld.so.conf ，将/usr/local/lib路径直接粘贴进去。
sudo ldconfig ---使上面的配置生效
注：如果ld.so.conf include的是另外的*.conf 找到这个conf添加进去 保存 （sudo vi /etc/ld.so.conf.d/libc.conf）
在linux中编译成库的
1. 配置
./configure --enable-static --disable-asm --enable-cross-compile --target-os=linux --arch=x86 --cross-prefix=/home/jetson/Documents/android-ndk-r22-linux-x86_64/android-ndk-r22/my-toolchain/bin/i686-linux-android- --prefix="/home/jetson/Documents/ffmpeg-snapshot/ffmpeg/ffmpeg_install" --enable-postproc
2. 编译：make -j7
3. 安装：make install（--prefix就是安装的路径）
然后库和头文件都安装到指定的路径上了
要链接的库和头文件，可以使用CFLAGS等环境变量
编译，最后要库和头文件
--disable-ffserver
缩减ffmpeg的大小：
./configure --disable-shared --disable-stripping --disable-ffmpeg --disable-ffplay --disable-ffprobe --disable-avdevice --disable-devices --disable-indevs --disable-outdevs --disable-debug --disable-asm --disable-yasm --disable-doc --disable-filters --disable-postproc --disable-bsfs --disable-encoders --disable-decoders --disable-parsers --disable-muxers --disable-demuxers --disable-protocols --enable-static --enable-small --enable-dct --enable-dwt --enable-lsp --enable-mdct --enable-rdft --enable-fft --enable-version3 --enable-nonfree --enable-bsf=aac_adtstoasc --enable-bsf=h264_mp4toannexb --enable-encoder=pcm_s16le --enable-encoder=aac --enable-encoder=libvo_aacenc --enable-decoder=aac --enable-decoder=mp3 --enable-decoder=pcm_s16le --enable-parser=aac --enable-muxer=flv --enable-muxer=wav --enable-muxer=adts --enable-demuxer=flv --enable-demuxer=wav --enable-demuxer=aac --enable-protocol=rtmp --enable-protocol=file --enable-cross-compile --target-os=linux --arch=x86 --cross-prefix=/home/jetson/Documents/android-ndk-r22-linux-x86_64/android-ndk-r22/my-toolchain/bin/i686-linux-android- --prefix="/home/jetson/Documents/ffmpeg-snapshot/ffmpeg/ffmpeg_install"
问题：
avformat_open_input：Invalid data found when processing input
在调用ffmpeg.so库的时候，遇到这个报错，是因为没有将需要的格式编译进来，进行完整编译之后，就不会报错了。
编译X264库
1. 配置
./configure --enable-static --disable-asm --enable-pic --host=i686-linux-android
2. 编译：make -j7
编译fdk-aac库
1. 配置
./configure --enable-static --host=i686-linux-android
2. 编译：make -j7
错误：
（1）找不到log.h
libSBRdec/src/lpp_tran.cpp:122:10: fatal error: 'log.h' file not found
#include <log.h>
^~~~~~~
1 error generated.
make: *** [Makefile:1575: libSBRdec/src/lpp_tran.lo] Error 1
make: *** Waiting for unfinished jobs....
（2）找不到android_errorWriteLog
libSBRdec/src/lpp_tran.cpp:342:5: error: use of undeclared identifier 'android_errorWriteLog'
android_errorWriteLog(0x534e4554, "112160868");
^
libSBRdec/src/lpp_tran.cpp:922:5: error: use of undeclared identifier 'android_errorWriteLog'
android_errorWriteLog(0x534e4554, "112160868");
^
CXX libFDK/src/mdct.lo
2 errors generated.
make: *** [Makefile:1575: libSBRdec/src/lpp_tran.lo] Error 1
make: *** Waiting for unfinished jobs....
解决办法：删掉即可
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