使用android-ndk-r17c构建ffmpeg 4.2.1时遇到的问题

1.报fatal error: asm/types.h: No such file or directory

/sysroot/usr/include/linux/types.h:21:23: fatal error: asm/types.h: No such file or directory
#include 

解决方案：在--extra-cflags添加头文件目录

--extra-cflags="-I$NDK/sysroot/usr/include -I$NDK/sysroot/usr/include/arm-linux-androideabi" \

2.报./libavutil/avassert.h:30:20: fatal error: stdlib.h: No such file or directory

./libavutil/avassert.h:30:20: fatal error: stdlib.h: No such file or directory

 #include 

解决方案：在--extra-cflags添加

--extra-cflags=" -isysroot $ISYSROOT"

完整的构建脚本如下：

# 配置NDK路径
NDK=/Users/kevinchen/android-ndk-r17c
# 指定了交叉编译环境,使其在编译过程中能够引用到 NDK 提供的原生标头和共享库文件
SYSROOT=$NDK/platforms/android-23/arch-arm/
ISYSROOT=$NDK/sysroot
TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64
#声明方法
function build_one
{
./configure --prefix=$PREFIX --enable-shared --disable-static --disable-doc --disable-ffmpeg --disable-ffplay --disable-ffprobe --disable-avdevice --disable-symver --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- --target-os=linux --arch=armeabi-v7a --enable-cross-compile --sysroot=$SYSROOT --extra-cflags="-Os -isysroot $ISYSROOT -fpic $ADDI_CFLAGS -I$NDK/sysroot/usr/include -I$NDK/sysroot/usr/include/arm-linux-androideabi" --extra-ldflags="$ADDI_LDFLAGS" $ADDITIONAL_CONFIGURE_FLAG
make clean
make
make install
}
CPU=armeabi-v7a
PREFIX=$(pwd)/android/$CPU
ADDI_CFLAGS="-marm"
build_one

编译中可能会遇到的一些错误

错误一

libavcodec/aaccoder.c: In function 'search_for_ms':
libavcodec/aaccoder.c:803:25: error: expected identifier or '(' before numeric constant
                     int B0 = 0, B1 = 0;
                         ^
libavcodec/aaccoder.c:865:28: error: lvalue required as left operand of assignment
                         B0 += b1+b2;
                            ^
libavcodec/aaccoder.c:866:25: error: 'B1' undeclared (first use in this function)
                         B1 += b3+b4;
                         ^
libavcodec/aaccoder.c:866:25: note: each undeclared identifier is reported only once for each function it appears in
make: *** [libavcodec/aaccoder.o] Error 1

解决：将libavcodec/aaccoder.c文件B0变量替换成b0

错误二

libavcodec/hevc_mvs.c: In function 'derive_spatial_merge_candidates':
libavcodec/hevc_mvs.c:208:15: error: 'y0000000' undeclared (first use in this function)
             ((y ## v) >> s->ps.sps->log2_min_pu_size))
               ^
libavcodec/hevc_mvs.c:204:14: note: in definition of macro 'TAB_MVF'
     tab_mvf[(y) * min_pu_width + x]
              ^
libavcodec/hevc_mvs.c:274:16: note: in expansion of macro 'TAB_MVF_PU'
     (cand && !(TAB_MVF_PU(v).pred_flag == PF_INTRA))
                ^
libavcodec/hevc_mvs.c:368:23: note: in expansion of macro 'AVAILABLE'
     is_available_b0 = AVAILABLE(cand_up_right, B0) &&
                       ^
libavcodec/hevc_mvs.c:208:15: note: each undeclared identifier is reported only once for each function it appears in
             ((y ## v) >> s->ps.sps->log2_min_pu_size))
               ^
libavcodec/hevc_mvs.c:204:14: note: in definition of macro 'TAB_MVF'
     tab_mvf[(y) * min_pu_width + x]
              ^
libavcodec/hevc_mvs.c:274:16: note: in expansion of macro 'TAB_MVF_PU'
     (cand && !(TAB_MVF_PU(v).pred_flag == PF_INTRA))
                ^
libavcodec/hevc_mvs.c:368:23: note: in expansion of macro 'AVAILABLE'
     is_available_b0 = AVAILABLE(cand_up_right, B0) &&
                       ^
libavcodec/hevc_mvs.c:207:15: error: 'x0000000' undeclared (first use in this function)
     TAB_MVF(((x ## v) >> s->ps.sps->log2_min_pu_size),                     \
               ^
libavcodec/hevc_mvs.c:204:34: note: in definition of macro 'TAB_MVF'
     tab_mvf[(y) * min_pu_width + x]
                                  ^
libavcodec/hevc_mvs.c:274:16: note: in expansion of macro 'TAB_MVF_PU'
     (cand && !(TAB_MVF_PU(v).pred_flag == PF_INTRA))
                ^
libavcodec/hevc_mvs.c:368:23: note: in expansion of macro 'AVAILABLE'
     is_available_b0 = AVAILABLE(cand_up_right, B0) &&
                       ^
libavcodec/hevc_mvs.c: In function 'ff_hevc_luma_mv_mvp_mode':
libavcodec/hevc_mvs.c:208:15: error: 'y0000000' undeclared (first use in this function)
             ((y ## v) >> s->ps.sps->log2_min_pu_size))
               ^
libavcodec/hevc_mvs.c:204:14: note: in definition of macro 'TAB_MVF'
     tab_mvf[(y) * min_pu_width + x]
              ^
libavcodec/hevc_mvs.c:274:16: note: in expansion of macro 'TAB_MVF_PU'
     (cand && !(TAB_MVF_PU(v).pred_flag == PF_INTRA))
                ^
libavcodec/hevc_mvs.c:683:24: note: in expansion of macro 'AVAILABLE'
     is_available_b0 =  AVAILABLE(cand_up_right, B0) &&
                        ^
libavcodec/hevc_mvs.c:207:15: error: 'x0000000' undeclared (first use in this function)
     TAB_MVF(((x ## v) >> s->ps.sps->log2_min_pu_size),                     \
               ^
libavcodec/hevc_mvs.c:204:34: note: in definition of macro 'TAB_MVF'
     tab_mvf[(y) * min_pu_width + x]
                                  ^
libavcodec/hevc_mvs.c:274:16: note: in expansion of macro 'TAB_MVF_PU'
     (cand && !(TAB_MVF_PU(v).pred_flag == PF_INTRA))
                ^
libavcodec/hevc_mvs.c:683:24: note: in expansion of macro 'AVAILABLE'
     is_available_b0 =  AVAILABLE(cand_up_right, B0) &&
                        ^
make: *** [libavcodec/hevc_mvs.o] Error 1

解决：将libavcodec/hevc_mvs.c文件的变量B0改成b0，xB0改成xb0，yB0改成yb0

问题三

libavcodec/opus_pvq.c: In function 'quant_band_template':
libavcodec/opus_pvq.c:498:9: error: expected identifier or '(' before numeric constant
     int B0 = blocks;
         ^
libavcodec/opus_pvq.c:559:12: error: lvalue required as left operand of assignment
         B0 = blocks;
            ^
make: *** [libavcodec/opus_pvq.o] Error 1

解决：将libavcodec/opus_pvq.c文件的变量B0改成b0

参考：https://www.jianshu.com/p/484db5ec733f