android - 很困惑，为什么我构建的 libffmpeg.so > 17M？

Question

我确实在 winxp 和 scientific linux 中为 Android 构建了 ffmpeg，ffmpeg 在 dolphin 播放器中——一个开源视频播放器 (http://code.google.com/p/dolphin-player/)，我只是构建ffmpeg，好像和rockplayer 1.7.0一样，都是用下面的build_andriod.sh，在winxp和linux下都能用， 并且都成功获取了bin/ffmpeg(小于5MB)，但是libffmpeg.so(>17MB)，当把libffmpeg.so放到dolphin-player libs中时，播放器无法播放，17MB太大了，原来的libffmpeg。所以在olphin-player libs不到5MB，请大家指点。

#!/bin/bash

######################################################
# FFmpeg builds script for Android+ARM platform
#
# This script is released under term of 
#   CDDL (http://www.opensource.org/licenses/cddl1) 
# Wrote by pinxue (~@gmail.com) from RockPlayer.com
#                                   2010-8 ~ 2011-4
######################################################

######################################################
# Usage:
#   put this script in top of FFmpeg source tree
#   ./build_android
#
# It generates binary for following architectures:
#     ARMv6 
#     ARMv6+VFP 
#     ARMv7+VFPv3-d16 (Tegra2) 
#     ARMv7+Neon (Cortex-A8)
#
# Customizing:
# 1. Feel free to change ./configure parameters for more features
# 2. To adapt other ARM variants
#       set $CPU and $OPTIMIZE_CFLAGS 
#       call build_one
######################################################

export TMPDIR=D:/tmp/android
export NDK=D:/android-ndk-r4

#PLATFORM=$NDK/build/platforms/android-8/arch-arm/
PLATFORM=$NDK/build/platforms/android-8/arch-arm
#PREBUILT=$NDK/build/prebuilt/darwin-x86/arm-eabi-4.4.0
PREBUILT=$NDK/build/prebuilt/windows/arm-eabi-4.4.0

function build_one
{

# -fasm : required. Android header file uses asm keyword instead of __asm__ , but most of c dialect (like ansi,c99,gnu99) implies -fno-asm.
#   ~/android/android-ndk-r4/build/platforms/android-5/arch-arm//usr/include/asm/byteorder.h: In function '___arch__swab32':
#   ~/android/android-ndk-r4/build/platforms/android-5/arch-arm//usr/include/asm/byteorder.h:25: error: expected ')' before ':' token

# -fno-short-enums : optimized.  Else FFmpeg obj will generate a huge number of warning for variable-size enums, 
#   though we may suppress them by --no-enum-size-warning, it would be better to avoid it.
#   .../ld: warning: cmdutils.o uses variable-size enums yet the output is to use 32-bit enums; use of enum values across objects may fail

# --extra-libs="-lgcc" : required. Else cannot solve some runtime function symbols
#   ... undefined reference to `__aeabi_f2uiz'

# --enable-protocols : required. Without this option, the file open always fails mysteriously.
#   FFmpeg's av_open_input_file will invoke file format probing functions, but because most of useful demuxers has flag of zero 
#   which cause them are ignored during file format probling and fall to url stream parsing,
#   if protocols are disabled, the file:// url cannot be opened as well.

# $PREBUILT/bin/arm-eabi-ar d libavcodec/libavcodec.a inverse.o : required.
#   FFmpeg includes two copies of inverse.c both in libavutil and libavcodec for performance consideration (not sure the benifit yet)
#   Without this step, final ld of generating libffmpeg.so will fail silently, if invoke ld through gcc, gcc will collect more reasonable error message.

# -llog: debug only, FFmpeg itself doesn't require it at all.
#   With this option, we may simply includes "utils/Log.h" and use LOGx() to observe FFmpeg's behavior
#   PS, it seems the toolchain implies -DNDEBUG somewhere, it would be safer to use following syntax
#    #ifdef NDEBUG
#        #undef NDEBUG
#        #define HAVE_NDEBUG
#    #endif
#    #include "utils/Log.h"
#    #ifdef HAVE_NDEBUG
#        #define NDEBUG
#        #undef HAVE_NDEBUG
#    #endif

# --whole-archive : required. Else ld generate a small .so file (about 15k)

# --no-stdlib : required. Android doesn't use standard c runtime but invited its own wheal (bionic libc) because of license consideration.

# space before \ of configure lines: required for some options. Else next line will be merged into previous lines's content and cause problem.
#   Especially the --extra-cflags, the next line will pass to gcc in this case and configure will say gcc cannot create executable.

# many options mentioned by articles over internet are implied by -O2 or -O3 already, need not repeat at all.

# two or three common optimization cflags are omitted because not sure about the trade off yet. invoke NDK build system with V=1 to find them.

# -Wl,-T,$PREBUILT/arm-eabi/lib/ldscripts/armelf.x mentioned by almost every articles over internet, but it is not required to specify at all.

# -Dipv6mr_interface=ipv6mr_ifindex : required. Android inet header doesn't use ipv6mr_interface which is required by rfc, seems it generate this user space header file directly from kernel header file, but Linux kernel has decided to keep its own name for ever and ask user space header to use rfc name.

# HAVE_SYS_UIO_H : required. Else:
# In file included from ~/android/android-ndk-r4/build/platforms/android-5/arch-arm//usr/include/linux/socket.h:29,
#                 from ~/android/android-ndk-r4/build/platforms/android-5/arch-arm//usr/include/sys/socket.h:33,
#                 from libavformat/network.h:35,
#                 from libavformat/utils.c:46:
#~/android/android-ndk-r4/build/platforms/android-5/arch-arm//usr/include/linux/uio.h:19: error: redefinition of 'struct iovec'
#

# --disable-doc : required because of strange bug of toolchain.
#

#
#--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"
#

./configure --target-os=linux \
    --prefix=$PREFIX \
    --enable-cross-compile \
    --extra-libs="-lgcc" \
    --arch=arm \
    --cc=$PREBUILT/bin/arm-eabi-gcc \
    --cross-prefix=$PREBUILT/bin/arm-eabi- \
    --nm=$PREBUILT/bin/arm-eabi-nm \
    --sysroot=$PLATFORM \
   --extra-cflags=" -O3 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 -Dipv6mr_interface=ipv6mr_ifindex -fasm -Wno-psabi -fno-short-enums  -fno-strict-aliasing -finline-limit=300 $OPTIMIZE_CFLAGS " \
    --disable-shared \
    --enable-static \
    --extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -nostdlib -lc -lm -ldl -llog" \
    --enable-parsers \
    --disable-encoders  \
    --enable-decoders \
    --disable-muxers \
    --enable-demuxers \
    --enable-swscale  \
    --disable-ffplay \
    --disable-ffprobe \
    --disable-ffserver \
    --enable-network \
    --enable-indevs \
    --disable-bsfs \
    --disable-filters \
    --enable-protocols  \
    --enable-asm \
    --disable-doc \
    $ADDITIONAL_CONFIGURE_FLAG

##make clean
make  -j4 install


$PREBUILT/bin/arm-eabi-ar d libavcodec/libavcodec.a inverse.o

$PREBUILT/bin/arm-eabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib  -soname libffmpeg.so -shared -nostdlib  -z,noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavformat/libavformat.a libavutil/libavutil.a  -lc -lm -lz -ldl -llog  --warn-once  --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-eabi/4.4.0/libgcc.a

}


#arm v6
CPU=armv6
OPTIMIZE_CFLAGS="-marm -march=$CPU"
PREFIX=./android/$CPU 
ADDITIONAL_CONFIGURE_FLAG=
build_one

#arm v7vfpv3
CPU=armv7-a
OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=vfpv3-d16 -marm -march=$CPU "
PREFIX=./android/$CPU 
ADDITIONAL_CONFIGURE_FLAG=
build_one

#arm v7vfp
CPU=armv7-a
OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=vfp -marm -march=$CPU "
PREFIX=./android/$CPU-vfp
ADDITIONAL_CONFIGURE_FLAG=
build_one

#arm v7n
CPU=armv7-a
OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=neon -marm -march=$CPU -mtune=cortex-a8"
PREFIX=./android/$CPU-neon 
ADDITIONAL_CONFIGURE_FLAG=--enable-neon
build_one

#arm v6+vfp
CPU=armv6
OPTIMIZE_CFLAGS="-DCMP_HAVE_VFP -mfloat-abi=softfp -mfpu=vfp -marm -march=$CPU"
PREFIX=./android/${CPU}_vfp 
ADDITIONAL_CONFIGURE_FLAG=
build_one

Answer 1

你应该剥离，剥离.so，添加这一行

$PREBUILT/bin/arm-eabi-strip -g $PREFIX/libffmpeg.so

下面

$PREBUILT/bin/arm-eabi-ld -rpath-link=$PLATFORM/usr/lib ...

那么 .so 的大小就足够小了，

但播放器可能仍然无法工作，libswscale/libswscale.a 应该添加到 libffmpeg.so 中，将其添加到这一行:

$PREBUILT/bin/arm-eabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -soname libffmpeg.so -shared -nostdlib -z,noexecstack -Bsymbolic --whole -archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavformat/libavformat.a libswscale/libswscale.a ...