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ffmpegbuild's Introduction

本项目将介绍如何编译FFmpeg在Android中使用

编译环境
系统：Windows 11
终端：msys2
Android Studio 版本：Hedgehog
NDK版本：21.4.7075529
FFmpeg版本：6.1

强烈建议：windows系统还是安装一个ubuntu的虚拟机吧，少踩很多坑

一、修改FFmpeg源码

既然要编译FFmpeg源码，那么就需要更改一些配置，大概就两步：

  • 下载FFmpeg源码，以及ndk-r22b

  • 进入下载的源码，编辑configure

将如下内容

SLIBNAME_WITH_MAJOR='$(SLIBNAME).$(LIBMAJOR)'
LIB_INSTALL_EXTRA_CMD='$$(RANLIB) "$(LIBDIR)/$(LIBNAME)"'
SLIB_INSTALL_NAME='$(SLIBNAME_WITH_VERSION)'
SLIB_INSTALL_LINKS='$(SLIBNAME_WITH_MAJOR) $(SLIBNAME)'

替换为

SLIBNAME_WITH_MAJOR='$(SLIBPREF)$(FULLNAME)-$(LIBMAJOR)$(SLIBSUF)'
LIB_INSTALL_EXTRA_CMD='$$(RANLIB)"$(LIBDIR)/$(LIBNAME)"'
SLIB_INSTALL_NAME='$(SLIBNAME_WITH_MAJOR)'
SLIB_INSTALL_LINKS='$(SLIBNAME)'
  • 在当前目录下新建build_android.sh文件，并写入以下内容：
#!/bin/bash
# 清空上次的编译
make clean
#你自己的NDK路径.
NDK=/home/anjoiner/Android/Sdk/ndk-bundle
TOOLCHAIN=$NDK/toolchains/llvm/prebuilt/linux-x86_64
SYSROOT=$TOOLCHAIN/sysroot
API=21

function build_android
{
echo "Compiling FFmpeg for $CPU"
./configure \
    --prefix=$PREFIX \
    --disable-static \
    --disable-doc \
    --disable-ffmpeg \
    --disable-ffplay \
    --disable-ffprobe \
    --disable-doc \
    --disable-symver \
    --enable-nonfree \
    --enable-gpl \
    --enable-small \
    --enable-neon \
    --enable-hwaccels \
    --enable-avdevice \
    --enable-postproc \
    --enable-shared \
    --enable-jni \
    --enable-mediacodec \
    --enable-decoder=h264_mediacodec \
    --cross-prefix=$CROSS_PREFIX \
    --target-os=android \
    --arch=$ARCH \
    --cpu=$CPU \
    --nm=$NM \
    --strip=$STRIP \
    --cc=$CC \
    --cxx=$CXX \
    --enable-cross-compile \
    --sysroot=$SYSROOT \
    --extra-cflags="-Os -fpic $OPTIMIZE_CFLAGS" \
    --extra-ldflags="$ADDI_LDFLAGS" \
    $ADDITIONAL_CONFIGURE_FLAG
make clean
make
make install
echo "The Compilation of FFmpeg for $CPU is completed"
}

#armv8-a
ARCH=aarch64-linux-android-
VERSION=arm64
CPU=armv8-a
CROSS_PREFIX=$TOOLCHAIN/bin/${ARCH}
CC=$TOOLCHAIN/bin/aarch64-linux-android$API-clang
CXX=$TOOLCHAIN/bin/aarch64-linux-android$API-clang++
NM=$TOOLCHAIN/bin/${ARCH}nm
STRIP=$TOOLCHAIN/bin/${ARCH}strip
PREFIX=$(pwd)/android/$CPU
OPTIMIZE_CFLAGS="-march=$CPU"
build_android

#armv7-a
ARCH=arm-linux-androideabi-
VERSION=arm
CPU=armv7-a
CROSS_PREFIX=$TOOLCHAIN/bin/${ARCH}
CC=$TOOLCHAIN/bin/armv7a-linux-androideabi$API-clang
CXX=$TOOLCHAIN/bin/armv7a-linux-androideabi$API-clang++
NM=$TOOLCHAIN/bin/${ARCH}nm
STRIP=$TOOLCHAIN/bin/${ARCH}strip
PREFIX=$(pwd)/android/$CPU
OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=neon -march=$CPU"
build_android

二、开始编译

在编译之前需要为刚刚我们创建的文件赋予执行权限

sudo chmod +x build_android.sh

然后就开始编译

./build_android.sh

经过漫长的等待...就会在源码目录下得到如下内容

三、ndk编译

上面得到的一系列so文件还不能直接使用，还需要进行如下配置

配置

  • 在任意目录下创建jni文件夹

  • 将刚刚编译出来的android/armv7-a/include下的所有目录拷贝进jni文件夹

  • 在jni下创建一个prebuilt文件夹

  • 将android/armv7-a/lib下所有的so文件拷贝进入prebuilt

  • 将源码下fftools文件夹下面的如下文件拷贝进入jni

    • cmdutils.c
    • cmdutils.h
    • ffmpeg_filter.c
    • ffmpeg_hw.c
    • ffmpeg_opt.c
    • ffmpeg.c
    • ffmpeg.h

  • 将源码下的config.h进入jni

编辑

  • 编辑 ffmpeg.c

将如下代码

int main(int argc, char **argv)

替换为

int run(int argc, char **argv)
  • 编辑 ffmpeg.h

在ffmpeg.h中增加int int run(int argc, char **argv);

...
int hw_device_setup_for_encode(OutputStream *ost);

int hwaccel_decode_init(AVCodecContext *avctx);
// add it
int run(int argc, char **argv);

#endif /* FFTOOLS_FFMPEG_H */
  • 编辑cmdutils.h 将如下内容
void show_help_children(const AVClass *class, int flags);

替换为

void show_help_children(const AVClass *clazz, int flags);

JNI

接下来就是开始使用jni去调用ffmpeg中的方法了

  • 在jni文件夹中创建ffmpeg-invoke.cpp，但是需要使用你自己的文件路径替换com_llhon_ffmpeg_FFmpegCmd
#include <jni.h>
#include <string.h>
#include "android/log.h"

#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, "ffmpeg-invoke", __VA_ARGS__)

extern "C"{
#include "ffmpeg.h"
#include "libavcodec/jni.h"
}

extern "C"
JNIEXPORT jint JNICALL
Java_com_llhon_ffmpeg_FFmpegCmd_run(JNIEnv *env, jclass type, jint cmdLen,
                                             jobjectArray cmd) {
    //set java vm
    JavaVM *jvm = NULL;
    env->GetJavaVM(&jvm);
    av_jni_set_java_vm(jvm, NULL);

    char *argCmd[cmdLen] ;
    jstring buf[cmdLen];

    for (int i = 0; i < cmdLen; ++i) {
        buf[i] = static_cast<jstring>(env->GetObjectArrayElement(cmd, i));
        char *string = const_cast<char *>(env->GetStringUTFChars(buf[i], JNI_FALSE));
        argCmd[i] = string;
        LOGD("argCmd=%s",argCmd[i]);
    }

    int retCode = run(cmdLen, argCmd);
    LOGD("ffmpeg-invoke: retCode=%d",retCode);

    return retCode;

}
  • 在jni文件夹中创建Android.mk，需要更改LOCAL_C_INCLUDES
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE :=  libavdevice
LOCAL_SRC_FILES := prebuilt/libavdevice.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE :=  libavutil
LOCAL_SRC_FILES := prebuilt/libavutil.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE :=  libswresample
LOCAL_SRC_FILES := prebuilt/libswresample.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE :=  libswscale
LOCAL_SRC_FILES := prebuilt/libswscale.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := libavcodec
LOCAL_SRC_FILES := prebuilt/libavcodec.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := libavformat
LOCAL_SRC_FILES := prebuilt/libavformat.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := libavfilter
LOCAL_SRC_FILES := prebuilt/libavfilter.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := libpostproc
LOCAL_SRC_FILES := prebuilt/libpostproc.so
include $(PREBUILT_SHARED_LIBRARY)


include $(CLEAR_VARS)
LOCAL_MODULE := ffmpeg-invoke

LOCAL_SRC_FILES :=ffmpeg-invoke.cpp \
                 cmdutils.c \
                 ffmpeg_filter.c \
                 ffmpeg_opt.c \
                 ffmpeg_hw.c \
                 ffmpeg.c

# 将此处的路径改为你ffmepg源码所在位置
LOCAL_C_INCLUDES := /home/llhon/develop/FFmpeg/ffmpeg-6.1

LOCAL_LDLIBS := -llog -ljnigraphics -lz -landroid -lm -pthread -L$(SYSROOT)/usr/lib
LOCAL_SHARED_LIBRARIES := libavdevice libavcodec libavfilter libavformat libavutil libswresample libswscale libpostproc

include $(BUILD_SHARED_LIBRARY)
  • 在jni文件夹中创建Application.mk
APP_ABI := armeabi-v7a
APP_PLATFORM := android-21
APP_OPTIM := release
APP_STL := c++_static
  • 在jni文件夹中执行ndk-build命令
/home/llhon/develop/Android/Sdk/ndk-bundle/ndk-build

如果发生以下错误：

1. D:/develop/workspace/android_ws/FFmpegBuild/app/src/main/jni/ffmpeg.h:896:35: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]

那就编辑ffmpeg.h，将如下内容

#define SPECIFIER_OPT_FMT_i64 "%"PRId64
#define SPECIFIER_OPT_FMT_ui64 "%"PRIu64

替换为

#define SPECIFIER_OPT_FMT_i64  "%" PRId64
#define SPECIFIER_OPT_FMT_ui64 "%" PRIu64
2. D:/develop/workspace/android_ws/FFmpegBuild/app/src/main/jni/ffmpeg.h:311:20: error: expected member name or ';' after declaration specifiers

编辑ffmpeg.h，将如下内容

typedef struct FilterGraph {
    const AVClass *class;

替换为

typedef struct FilterGraph {
    const AVClass *clazz;
3. D:/develop/workspace/android_ws/FFmpegBuild/app/src/main/jni/libavcodec/packet.h:787:6: note: candidate function not viable: cannot convert argument of incomplete type 'void *' to 'AVPacket *' for 1st argument

编辑libavcodec/packet.h，将如下内容

static inline void pkt_move(void *dst, void *src)

改为

static inline void pkt_move(AVPacket *dst, AVPacket *src)
4. D:/develop/workspace/android_ws/FFmpegBuild/app/src/main/jni/ffmpeg.c:795: error: undefined reference to 'fix_sub_duration_heartbeat'

未链接到某些资源文件： 可能的情况是jni文件夹内缺少 ffmpeg 某个源码文件，可以进入D:\develop\workspace\android_ws\FFmpeg-release-6.1\fftools文件夹内是否有需要链接的文件 copy 到jni文件夹

再次执行ndk-build命令，大概会得到如下内容，那就说明编译完成了

四、如何将多个so文件合并成一个独立的so文件

1. 在 build_android.sh 文件里添加以下代码：

# 打包，以下代码是为了把7个so包合成一个so包，如果不需要合成可以去掉这段代码
echo "开始编译libffmpeg-org.so"
$TOOLCHAIN/bin/$ARC-ld \
    -rpath-link=$SYSROOT/usr/lib/$ARC/$API \
    -L$SYSROOT/usr/lib/$ARC/$API \
    -L$TOOLCHAIN/lib/gcc/$ARC/4.9.x \
    -L$PREFIX/lib -soname libffmpeg-org.so \
    -shared -Bsymbolic --whole-archive --no-undefined -o \
    $PREFIX/libffmpeg-org.so \
    $PREFIX/lib/libavcodec.a \
    $PREFIX/lib/libavfilter.a \
    $PREFIX/lib/libswresample.a \
    $PREFIX/lib/libavformat.a \
    $PREFIX/lib/libavutil.a \
    $PREFIX/lib/libswscale.a \
    $PREFIX/lib/libavdevice.a \
    $PREFIX/lib/libpostproc.a \
    -lc -lm -lz -ldl -llog -landroid --dynamic-linker=/system/bin/linker \
    $TOOLCHAIN/lib/gcc/$ARC/4.9.x/libgcc_real.a || exit 1

echo "完成编译libffmpeg-org.so"

2. 在 MSYS2 CLANG64 终端命令行中执行 ./build_android.sh 脚本文件

完整的脚本代码参考scripts/build_android.sh

3. 如果遇到以下错误：

1. libswscale.a(half2float.o): multiple definition of 'ff_init_half2float_tables'; libavcodec.a(half2float.o): previous definition here

编译.a文件时，libavcodec.a和libswscale.a包含同一个half2float.o，在链接 libavcodec.a 和 libswscale.a 时会出现函数重定义的错误。需要在执行脚本之前修改libswscale 文件夹下的 Makefile ，将 OBJS 下的 half2float.o 删除即可

2. libavfilter/vf_pp.c:59: error: undefined reference to 'pp_get_mode_by_name_and_quality'；libavfilter/vf_pp.c:164: error: undefined reference to 'pp_free_mode'

这一般是由于链接时找不到对应的库报的错误，在 build_android.sh 脚本文件里检查下是否有链接 libpostproc.a 文件

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