用NDK编译FFmpeg

最近在研究Android实时视频采集这块，根据以下内容移植FFmpeg成功，网上转载而来以备以后忘记，如果有做这方面的同学我们可以一起交流学习。

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Android内置的编解码器实在太少，于是我们需要FFmpeg。Android提供了NDK，为我们使用FFmpeg这种C语言代码提供了方便。
首先创建一个标准的Android项目vPlayer

android create project -n vPlayer -t 8 -p vPlayer -k me.abitno.vplayer -a PlayerView

然后在vPlayer目录里

mkdir jni && cd jniwget http://ffmpeg.org/releases/ffmpeg-0.6.tar.bz2tar xf ffmpeg-0.6.tar.bz2 && mv ffmpeg-0.6 ffmpeg && cd ffmpeg

在ffmpeg下新建一个config.sh，内容如下，注意把PREBUILT和PLATFORM设置正确。另外里面有些参数你也可以自行调整，我主要是为了配置一个播放器而这样设置的。

#!/bin/bashPREBUILT=/home/abitno/Android/android-ndk-r4/build/prebuilt/linux-x86/arm-eabi-4.4.0PLATFORM=/home/abitno/Android/android-ndk-r4/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"

运行config.sh开始configure

chmod +x config.sh./config.sh

 

configure完成后，编辑刚刚生成的config.h，找到这句

#define restrict restrict

Android的GCC不支持restrict关键字，于是修改成下面这样

#define restrict

 

编辑libavutil/libm.h，把其中的static方法都删除。

分别修改libavcodec、libavfilter、libavformat、libavutil、libpostproc和libswscale下的Makefile，把下面两句删除

include $(SUBDIR)../subdir.makinclude $(SUBDIR)../config.mak

在ffmpeg下添加一个文件av.mk，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))

接下来要添加一系列的Android.mk，在jni根目录下的内容如下

include $(all-subdir-makefiles)

在ffmpeg目录下，Android.mk

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

 

libavformat/Android.mk

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)

libavcodec/Android.mk

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)

 

libavfilter、libavutil、libpostproc和libswscale下的Android.mk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)

 

最外层的jni/Android.mk和jni/ffmpeg/Android.mk只是随便这样写的，你应该根据自己的需求改写。