Compile linphone-android souce error
1.Compile error：
Compile arm    : vpx <= vp8_vpxyv12_copysrcframe_func_neon.s
Compile arm    : vpx <= vp8_vpxyv12_extendframeborders_neon.s
make: *** No rules to create“/home/ha/prj/android/workspace/linphone/linphone-android/obj/local/armeabi-v7a/objs/vpx/vpx_scale/arm/neon/yv12extend_arm.o”need target“/home/ha/prj/android/workspace/linphone/linphone-android/jni/..//submodules/externals/build/libvpx/../../libvpx/vpx_scale/arm/neon/yv12extend_arm.c”. Stopped

Reason:
  In submodules/externals/build/libvpx/Android.mk L30:
#neon
SCALE_SRCS += vpx_scale/arm/neon/vp8_vpxyv12_copyframe_func_neon$(ASM).neon
SCALE_SRCS += vpx_scale/arm/neon/vp8_vpxyv12_copyframeyonly_neon$(ASM).neon
SCALE_SRCS += vpx_scale/arm/neon/vp8_vpxyv12_copysrcframe_func_neon$(ASM).neon
SCALE_SRCS += vpx_scale/arm/neon/vp8_vpxyv12_extendframeborders_neon$(ASM).neon
SCALE_SRCS += vpx_scale/arm/neon/yv12extend_arm.c
But there has no yv12extend_arm.c file in directory "neon", it is in parent directory

Solve: 
   Modify Android.mk
SCALE_SRCS += vpx_scale/arm/neon/yv12extend_arm.c modify to
SCALE_SRCS += vpx_scale/arm/yv12extend_arm.c
OR
 copy yv12extend_arm.c from vpx_scale/arm to /vpx_scale/arm/none.

2.Compile error:
Compile arm    : vpx <= vp8_subtract_armv6.s
make: *** No rules to create“/home/ha/prj/android/workspace/linphone/linphone-android/obj/local/armeabi-v7a/objs/vpx/vp8/encoder/arm/armv6/vp8_short_fdct4x4_armv6.o”need target“/home/ha/prj/android/workspace/linphone/linphone-android/jni/..//submodules/externals/build/libvpx/../../libvpx/vp8/encoder/arm/armv6/vp8_short_fdct4x4_armv6.s”. Stopped
Reason:
  There has the file vp8_fast_fdct4x4_armv6.s instead of vp8_short_fdct4x4_armv6.s in director "libvpx/vp8/encoder/arm/armv6"
Solve: 
   Modify submodules/externals/build/libvpx/Android.mk 
#VP8_CX_SRCS += vp8/encoder/arm/armv6/vp8_short_fdct4x4_armv6$(ASM) 
change it to
VP8_CX_SRCS += vp8/encoder/arm/armv6/vp8_fast_fdct4x4_armv6$(ASM)

3.Compile error：
Compile arm    : vpx <= walsh_v6.s
Compile arm    : vpx <= fastquantizeb_neon.s
make: *** No rules to create“/home/ha/prj/android/workspace/linphone/linphone-android/obj/local/armeabi-v7a/objs/vpx/vp8/encoder/arm/neon/picklpf_arm.o”need target“/home/ha/prj/android/workspace/linphone/linphone-android/jni/..//submodules/externals/build/libvpx/../../libvpx/vp8/encoder/arm/neon/picklpf_arm.c”.Stopped
Reason:
  There has no picklpf_arm.c file in directory "libvpx/vp8/encoder/arm/neon", it is in parent directory 
Solve: 
  Copy the file picklpf_arm.c from parent directory to directory "none"

4.Compile error：
/home/ha/prj/android/workspace/linphone/linphone-android/obj/local/armeabi-v7a/libvpx.a(entropy.o): In function `vp8_default_coef_probs':
/home/ha/prj/android/workspace/linphone/linphone-android/jni/..//submodules/externals/build/libvpx/../../libvpx/vp8/common/entropy.c:186: undefined reference to `vp8_default_coef_counts'
Solve: 
 Add "defaultcoefcounts.c" to submodules/externals/build/libvpx/Android.mk 
VP8_COMMON_SRCS += vp8/common/debugmodes.c
@address@hidden add
VP8_COMMON_SRCS += vp8/common/defaultcoefcounts.c

5.Compile error：
/home/ha/prj/android/workspace/linphone/linphone-android/obj/local/armeabi-v7a/libvpx.a(arm_csystemdependent.o): In function `vp8_arch_arm_encoder_init':
/home/ha/prj/android/workspace/linphone/linphone-android/jni/..//submodules/externals/build/libvpx/../../libvpx/vp8/encoder/arm/arm_csystemdependent.c:137: undefined reference to `vp8_fast_fdct4x4_neon'
Solve: 
 Add some option to submodules/externals/build/libvpx/Android.mk 
VP8_CX_SRCS += vp8/encoder/arm/neon/vp8_shortwalsh4x4_neon$(ASM).neon
@address@hidden add
VP8_CX_SRCS += vp8/encoder/arm/neon/fastfdct8x4_neon$(ASM).neon
VP8_CX_SRCS += vp8/encoder/arm/neon/fastfdct4x4_neon$(ASM).neon