Encoding
I420 (YUV), RGB24:?http://blog.csdn.net/leixiaohua1020/article/details/12234821
1. I420????????A frame in I420 (YUV 4:2:0) is size = width * height * 1.5Byte
? ? ????????????????I420 is YYYY…UUUUVVVV
????????????????????NV21 is YYYY…UVUVUVUV (Maybe used in the deprecated Camera API)
????????????????????YV12 IS YYYY…VVVVUUUU?(Maybe used in the deprecated Camera API)
2. RGB24????A frame in RGB24 is size = width * height * 3Byte
Camera2 API
Usage
1. Official guide:?https://developer.android.com/guide/topics/media/camera
2. Official samples
? ? ? ? a.?https://github.com/googlesamples/android-Camera2Basic/
? ? ? ? b.?https://github.com/googlesamples/android-Camera2Raw/
? ? ? ? c.?https://github.com/googlesamples/android-Camera2Video/
Format
1. Image class:?https://www.polarxiong.com/archives/Android-Image%E7%B1%BB%E6%B5%85%E6%9E%90-%E7%BB%93%E5%90%88YUV_420_888.html
2.?YUV_420_888 to I420:?https://www.polarxiong.com/archives/Android-YUV_420_888%E7%BC%96%E7%A0%81Image%E8%BD%AC%E6%8D%A2%E4%B8%BAI420%E5%92%8CNV21%E6%A0%BC%E5%BC%8Fbyte%E6%95%B0%E7%BB%84.html
Open Source Libs
1. libyuv
? ? ? ? It is used to rotate, crop and scale the captured video frames before transfer. The frames must be head-up no matter the phone orientation. The best order of image processing for downscaling the captured image is: scale -> crop -> rotate.
? ??????Use Neon to optimize the libyuv when compiling, so that we can do parallel processing.
2. libtheora
? ? ? ? Use the unofficial libtheora 1.2 with?neon optimization. Need to change the instruction “BLX” in lib/arm/armenquant.s to “BL” to avoid crush issue.
????????1).????Get the tools:
????????????????a.????sudo apt-get install autoconf
????????????????b.????sudo apt-get install libtool
????????????????c.????sudo apt-get install libogg-dev
????????2).????set up the ndk build evn:
????????????????a.????NDK=/build/toolchain/lin64/android-ndk-r12b
????????????????b.????SYSROOT=$NDK/platforms/android-19/arch-arm (Use API Level 19 because the libogg and libtheora are too old to be compiled on newer platform)
????????????????c.????PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64
????????3).????Build the libogg:
????????????????a.????./autogen.sh --prefix=$HOME/tmp/libogg --host=arm-linux --enable-shared CC="$PREBUILT/bin/arm-linux-androideabi-gcc --sysroot=$SYSROOT" LDFLAGS="-Wl,-O2,--as-needed" CFLAGS="-march=armv7-a -mfpu=neon"
????????????????b.????make install
????????4).????Build the libtheora
????????????????ARM compile options?https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html
????????????????Into Assambly:?http://www.cnblogs.com/goodhacker/p/3206405.htmlhttp://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0204ic/Cihfddaf.html
????????????????a.????./autogen.sh --prefix=$HOME/tmp/libtheora --host=arm-linux --disable-examples CC="$PREBUILT/bin/arm-linux-androideabi-gcc --sysroot=$SYSROOT" LDFLAGS="-Wl,-O2,-g,-L$HOME/tmp/libogg/lib" CPPFLAGS="-I$HOME/tmp/libogg/include" CFLAGS="-march=armv7-a -mfpu=neon -mthumb "
????????????????b.????make install
