ffmpeg 编译至android

ffmpeg 版本0.65

ndk 版本 5c

编写 mk 文件

在 /root/ffmpeg/jni 目录中创建一个 Android.mk 文件，内容如下
```
include $(all-subdir-makefiles)
```

在 /root/ffmpeg/jni/ffmpeg-0.6.1 目录中创建一个 Android.mk 文件，内容如下

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_WHOLE_STATIC_LIBRARIES := libavformat libavcodec libavutil libpostproc libswscaleLOCAL_MODULE := ffmpeginclude $(BUILD_SHARED_LIBRARY)include $(call all-makefiles-under,$(LOCAL_PATH))

在 /root/ffmpeg/jni/ffmpeg-0.6.1 目录中创建一个 av.mk 文件，内容如下

# LOCAL_PATH is one of libavutil, libavcodec, libavformat, or libswscale#include $(LOCAL_PATH)/../config-$(TARGET_ARCH).makinclude $(LOCAL_PATH)/../config.makOBJS :=OBJS-yes :=MMX-OBJS-yes :=include $(LOCAL_PATH)/Makefile# collect objectsOBJS-$(HAVE_MMX) += $(MMX-OBJS-yes)OBJS += $(OBJS-yes)FFNAME := lib$(NAME)FFLIBS := $(foreach,NAME,$(FFLIBS),lib$(NAME))FFCFLAGS  = -DHAVE_AV_CONFIG_H -Wno-sign-compare -Wno-switch -Wno-pointer-signFFCFLAGS += -DTARGET_CONFIG=\"config-$(TARGET_ARCH).h\"ALL_S_FILES := $(wildcard $(LOCAL_PATH)/$(TARGET_ARCH)/*.S)ALL_S_FILES := $(addprefix $(TARGET_ARCH)/, $(notdir $(ALL_S_FILES)))ifneq ($(ALL_S_FILES),)ALL_S_OBJS := $(patsubst %.S,%.o,$(ALL_S_FILES))C_OBJS := $(filter-out $(ALL_S_OBJS),$(OBJS))S_OBJS := $(filter $(ALL_S_OBJS),$(OBJS))elseC_OBJS := $(OBJS)S_OBJS :=endifC_FILES := $(patsubst %.o,%.c,$(C_OBJS))S_FILES := $(patsubst %.o,%.S,$(S_OBJS))FFFILES := $(sort $(S_FILES)) $(sort $(C_FILES))

在 /root/ffmpeg/jni/ffmpeg-0.6.1/libavcodec 目录中创建一个 Android.mk 文件，内容如下

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)include $(LOCAL_PATH)/../av.mkLOCAL_SRC_FILES := $(FFFILES)LOCAL_C_INCLUDES :=        \    $(LOCAL_PATH)        \    $(LOCAL_PATH)/..LOCAL_CFLAGS += $(FFCFLAGS)LOCAL_LDLIBS := -lzLOCAL_STATIC_LIBRARIES := $(FFLIBS)LOCAL_MODULE := $(FFNAME)include $(BUILD_STATIC_LIBRARY)

在 /root/ffmpeg/jni/ffmpeg-0.6.1/libavformat 目录中创建一个 Android.mk 文件，内容如下

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)include $(LOCAL_PATH)/../av.mkLOCAL_SRC_FILES := $(FFFILES)LOCAL_C_INCLUDES :=        \    $(LOCAL_PATH)        \    $(LOCAL_PATH)/..LOCAL_CFLAGS += $(FFCFLAGS)LOCAL_CFLAGS += -include "string.h" -Dipv6mr_interface=ipv6mr_ifindexLOCAL_LDLIBS := -lzLOCAL_STATIC_LIBRARIES := $(FFLIBS)LOCAL_MODULE := $(FFNAME)include $(BUILD_STATIC_LIBRARY)

在 libavfilter、libavutil、libpostproc 和 libswscale 目录中各创建一个 Android.mk 文件，内容如下

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)include $(LOCAL_PATH)/../av.mkLOCAL_SRC_FILES := $(FFFILES)LOCAL_C_INCLUDES :=        \    $(LOCAL_PATH)        \    $(LOCAL_PATH)/..LOCAL_CFLAGS += $(FFCFLAGS)LOCAL_STATIC_LIBRARIES := $(FFLIBS)LOCAL_MODULE := $(FFNAME)include $(BUILD_STATIC_LIBRARY)

修改 libm.h 文件和 Makefile 文件

编辑 /root/ffmpeg/jni/ffmpeg-0.6.1/libavutil 目录中的 libm.h 文件，删除以下 static 方法

#if !HAVE_LRINTstatic av_always_inline av_const longint lrint(double x){    return rint(x);}#endif/* HAVE_LRINT */#if !HAVE_LRINTFstatic av_always_inline av_const longint lrintf(float x){    return (int)(rint(x));}#endif/* HAVE_LRINTF */#if !HAVE_ROUNDstatic av_always_inline av_const double round(double x){    return (x > 0) ? floor(x + 0.5) : ceil(x - 0.5);}#endif/* HAVE_ROUND */#if !HAVE_ROUNDFstatic av_always_inline av_const float roundf(float x){    return (x > 0) ? floor(x + 0.5) : ceil(x - 0.5);}#endif/* HAVE_ROUNDF */#if !HAVE_TRUNCFstatic av_always_inline av_const float truncf(float x){    return (x > 0) ? floor(x) : ceil(x);}#endif/* HAVE_TRUNCF */

编辑 libavcodec、libavfilter、libavformat、libavutil、libpostproc 和 libswscale 目录中的 Makefile 文件，删除
```
include $(SUBDIR)../subdir.mak
```
和
```
include $(SUBDIR)../config.mak
```

生成 config.h 文件

在 /root/ffmpeg/jni/ffmpeg-0.6.1 目录中创建一个 config.sh 文件，使用 Android NDK r4b 编译时内容如下

PREBUILT=/root/android-ndk-r4b/build/prebuilt/linux-x86/arm-eabi-4.4.0PLATFORM=/root/android-ndk-r4b/build/platforms/android-8/arch-arm./configure --target-os=linux \    --arch=arm \    --enable-version3 \    --enable-gpl \    --enable-nonfree \    --disable-stripping \    --disable-ffmpeg \    --disable-ffplay \    --disable-ffserver \    --disable-ffprobe \    --disable-encoders \    --disable-muxers \    --disable-devices \    --disable-protocols \    --enable-protocol=file \    --enable-avfilter \    --disable-network \    --disable-mpegaudio-hp \    --disable-avdevice \    --enable-cross-compile \    --cc=$PREBUILT/bin/arm-eabi-gcc \    --cross-prefix=$PREBUILT/bin/arm-eabi- \    --nm=$PREBUILT/bin/arm-eabi-nm \    --extra-cflags="-fPIC -DANDROID" \    --disable-asm \    --enable-neon \    --enable-armv5te \    --extra-ldflags="-Wl,-T,$PREBUILT/arm-eabi/lib/ldscripts/armelf.x -Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib $PREBUILT/lib/gcc/arm-eabi/4.4.0/crtbegin.o $PREBUILT/lib/gcc/arm-eabi/4.4.0/crtend.o -lc -lm -ldl"

使用 Android NDK r5 编译时内容如下

#!/bin/bashPREBUILT=/root/android-ndk-r5/toolchains/arm-eabi-4.4.0/prebuilt/linux-x86PLATFORM=/root/android-ndk-r5/platforms/android-8/arch-arm./configure --target-os=linux \    --arch=arm \    --enable-version3 \    --enable-gpl \    --enable-nonfree \    --disable-stripping \    --disable-ffmpeg \    --disable-ffplay \    --disable-ffserver \    --disable-ffprobe \    --disable-encoders \    --disable-muxers \    --disable-devices \    --disable-protocols \    --enable-protocol=file \    --enable-avfilter \    --disable-network \    --disable-mpegaudio-hp \    --disable-avdevice \    --enable-cross-compile \    --cc=$PREBUILT/bin/arm-eabi-gcc \    --cross-prefix=$PREBUILT/bin/arm-eabi- \    --nm=$PREBUILT/bin/arm-eabi-nm \    --extra-cflags="-fPIC -DANDROID" \    --disable-asm \    --enable-neon \    --enable-armv5te \    --extra-ldflags="-Wl,-T,$PREBUILT/arm-eabi/lib/ldscripts/armelf.x -Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib $PREBUILT/lib/gcc/arm-eabi/4.4.0/crtbegin.o $PREBUILT/lib/gcc/arm-eabi/4.4.0/crtend.o -lc -lm -ldl"

打开终端，进入 /root/ffmpeg/jni/ffmpeg-0.6.1 目录，运行下面的命令
```
chmod +x config.sh./config.sh
```
编辑 /root/ffmpeg/jni/ffmpeg-0.6.1 目录中的 config.h 文件，将
```
#define restrict restrict
```
修改为
```
#define restrict
```

四、开始编译 FFmpeg

很多人在用 havlenapetr 的方法编译 FFmpeg 时只得到一个 1599 字节 1.6KB 大小的 libffmpeg.so 文件，无论是用 Android NDK r4b 编译还是用 Android NDK r5 编译结果都是如此，很让人抓狂。我也很郁闷，最后花时间研究了一下 NDK，终于发现了解决方法，而且 Android NDK r4b 和 Android NDK r5 的情况还是完全不同的，请继续往下读。

使用 Android NDK r4b 编译
打开 android-ndk-r4b/build/toolchains/arm-eabi-4.4.0 目录中的 setup.mk 文件，你会发现 Google 在里面定义了一个用于编译动态库的 cmd-build-shared-library 函数。在cmd-build-shared-library 函数中 Google 使用了 PRIVATE_WHOLE_STATIC_LIBRARIES 函数。但是你在 android-ndk-r4b/build/core 目录中的 build-binary.mk 文件里却找不到 PRIVATE_WHOLE_STATIC_LIBRARIES 函数…… 外？WHY？终于搞清楚了，原来得不到正确的 libffmpeg.so 文件不是我的错，而是 Android NDK r4b 的 BUG！你妹啊！你大爷啊！坑爹呢这是！发布前不做测试吗！居然漏掉一个函数！！！（我敢说这是个 BUG 是因为 Google 在 Android NDK r5 中修复了这个 BUG）

木办法，只好手动替 Google 修补这个 BUG。好在修改方法很简单，只需要照 build-binary.mk 文件里的 PRIVATE_STATIC_LIBRARIES 增加一个 PRIVATE_WHOLE_STATIC_LIBRARIES 就行了。具体方法见下图

修改前的 build-binary.mk 文件

修改后的 build-binary.mk 文件

保存 build-binary.mk 文件之后，运行下面的命令编译
```
/root/android-ndk-r4b/ndk-build NDK_PROJECT_PATH=/root/ffmpeg
```
接着你会看到 warning 不停的出现在屏幕上，熬过这段心惊肉跳的时间之后，你会看到 libffmpeg.so 文件已经被编译生成了。

看看 /root/ffmpeg/obj/local/armeabi 目录中的 libffmpeg.so 文件，文件大小是 12.2MB

再看看 /root/ffmpeg/libs/local/armeabi 目录中的 libffmpeg.so 文件，文件大小是 3.2MB
使用 Android NDK r5 编译
打开 android-ndk-r5/build/core 目录中的 build-binary.mk 文件，发现 Google 这次没有忘记 PRIVATE_WHOLE_STATIC_LIBRARIES，但还最后编译得到的 libffmpeg.so 文件大小还是不正确。这次的问题是，android-ndk-r5 默认是使用 arm-linux-androideabi-4.4.3 编译，而不是 arm-eabi-4.4.0。但 android-ndk-r5/toolchains/arm-linux-androideabi-4.4.3 目录中的 setup.mk 文件里定义的 cmd-build-shared-library 函数并没有将静态库文件链接在一起生成动态库文件。所以解决的办法就是在执行 ndk-build 时加上 NDK_TOOLCHAIN 参数，指定使用 arm-eabi-4.4.0 来编译。完整命令如下
```
/root/android-ndk-r5/ndk-build NDK_PROJECT_PATH=/root/ffmpeg NDK_TOOLCHAIN=arm-eabi-4.4.0 NDK_PLATFORM=android-8
```

/* * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA *//** * @file * Replacements for frequently missing libm functions */#ifndef AVUTIL_LIBM_H#define AVUTIL_LIBM_H#include <math.h>#include "config.h"#include "attributes.h"#if !HAVE_EXP2#undef exp2#define exp2(x) exp((x) * 0.693147180559945)#endif /* HAVE_EXP2 */#if !HAVE_EXP2F#undef exp2f#define exp2f(x) ((float)exp2(x))#endif /* HAVE_EXP2F */#if !HAVE_LLRINT#undef llrint#define llrint(x) ((long long)rint(x))#endif /* HAVE_LLRINT */#if !HAVE_LLRINTF#undef llrintf#define llrintf(x) ((long long)rint(x))#endif /* HAVE_LLRINT */#if !HAVE_LOG2#undef log2#define log2(x) (log(x) * 1.44269504088896340736)#endif /* HAVE_LOG2 */#if !HAVE_LOG2F#undef log2f#define log2f(x) ((float)log2(x))#endif /* HAVE_LOG2F */#if !HAVE_LRINT#undef lrint#define lrint(x) ((long int)(rint((double)x)))#endif /* HAVE_LRINT */#if !HAVE_LRINTF#undef lrintf#define lrintf(x) ((long int)(rint((float)x)))#endif /* HAVE_LRINTF */#if !HAVE_ROUND#undef round#define round(x) ((double)(((double)x > 0) ? floor((double)x + 0.5) : ceil((double)x - 0.5)))#endif /* HAVE_ROUND */#if !HAVE_ROUNDF#undef roundf#define roundf(x) ((float)(((float)x > 0) ? floor((float)x + 0.5) : ceil((float)x - 0.5)))#endif /* HAVE_ROUNDF */#if !HAVE_TRUNCF#undef truncf#define truncf(x) ((float)(((float)x > 0) ? floor((float)x) : ceil((float)x)))#endif /* HAVE_TRUNCF */#endif /* AVUTIL_LIBM_H */

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := LIB1LOCAL_SRC_FILES := libavcodec.ainclude $(PREBUILT_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := LIB2LOCAL_SRC_FILES := libavformat.ainclude $(PREBUILT_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := LIB3LOCAL_SRC_FILES := libavutil.ainclude $(PREBUILT_STATIC_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE    := hello-jniLOCAL_SRC_FILES := hello-jni.cLOCAL_STATIC_LIBRARIES := LIB1 LIB2 LIB3include $(BUILD_SHARED_LIBRARY)

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := avcodec
LOCAL_SRC_FILES := libavcodec.a
LOCAL_CFLAGS :=-Ilibavcodec
LOCAL_EXPORT_C_INCLUDES := libavcodec
LOCAL_EXPORT_CFLAGS := -Ilibavcodec
LOCAL_EXPORT_LDLIBS := -llog
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := avformat
LOCAL_SRC_FILES := libavformat.a
LOCAL_CFLAGS :=-Ilibavformat
LOCAL_EXPORT_C_INCLUDES := libavformat
LOCAL_EXPORT_CFLAGS := -Ilibavformat
LOCAL_EXPORT_LDLIBS := -llog
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := avutil
LOCAL_SRC_FILES := libavutil.a
LOCAL_CFLAGS :=-Ilibavutil
LOCAL_EXPORT_C_INCLUDES := libavutil
LOCAL_EXPORT_CFLAGS := -Ilibavutil
LOCAL_EXPORT_LDLIBS := -llog

include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := swscale
LOCAL_SRC_FILES :=libswscale.a
LOCAL_CFLAGS :=-Ilibswscale
LOCAL_EXPORT_C_INCLUDES := libswscale
LOCAL_EXPORT_CFLAGS := -I$libswscale
LOCAL_EXPORT_LDLIBS := -llog
include $(PREBUILT_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := hello-jni
LOCAL_SRC_FILES := hello-jni.c
LOCAL_LDLIBS := -L$(LOCAL_PATH) -lm -lz -lbz2
LOCAL_STATIC_LIBRARIES := avcodec avformat avutil swscale

include $(BUILD_SHARED_LIBRARY)

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