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• Understanding the VP8 Token Tree

  7 juin 2010, par Multimedia Mike — VP8

  I got tripped up on another part of the VP8 decoding process today. So I drew a picture to help myself understand it. Then I went back and read David Conrad’s comment on my last post regarding my difficulty understanding the VP8 spec and saw that he ran into the same problem. Since we both experienced the same hindrance in trying to sort out this matter, I thought I may as well publish the picture I drew.

  VP8 defines various trees for decoding different syntax elements. There is one tree for decoding the tokens and it is expressed in the VP8 spec as such :

  PLAIN TEXT

  C :

  1. const tree_index coef_tree [2 * (num_dct_tokens - 1)] =
  2. {
  3.  -dct_eob, 2,        /* eob = "0"  */
  4.   -DCT_0, 4,        /* 0  = "10" */
  5.   -DCT_1, 6,        /* 1  = "110" */
  6.    8, 12,
  7.    -DCT_2, 10,      /* 2  = "11100" */
  8.     -DCT_3, -DCT_4,    /* 3  = "111010", 4 = "111011" */
  9.    14, 16,
  10.     -dct_cat1, -dct_cat2, /* cat1 = "111100", cat2 = "111101" */
  11.    18, 20,
  12.     -dct_cat3, -dct_cat4, /* cat3 = "1111100", cat4 = "1111101" */
  13.     -dct_cat5, -dct_cat6 /* cat4 = "1111110", cat4 = "1111111" */
  14. } ;

  Here is what the table looks like when you make a tree out of it (click for full size image) :

  
  
  

  The catch is that it makes no sense for an end-of-block (EOB) token to follow a 0 token since EOB already indicates that the remainder of the coefficients should be 0 anyway. Thus, the spec states that, "decoding of certain DCT coefficients may skip the first branch, whose preceding coefficient is a DCT_0." I confess, I didn’t understand what "skip the first branch" meant until I drew the tree.

  
  
  

  For those wondering why it might be sub-optimal (clarity-wise) for a spec to simply regurgitate vast chunks of C code, this makes a decent case. As you can see, the spec makes certain assumptions about how a binary tree should be organized in a static array (node n points to elements n*2 and n*2+1 as its branches ; leaves are either negative or 0). This is the second method I have seen ; another piece of code (not the VP8 spec) had the nodes in the first half of the array and pointed to leaves in the second half. There must be other arrangements.

• libx264 encoder error in ffmpeg android build

  26 décembre 2013, par kerim yucel

  Right now, I have a ffmeg build script which recognizes libx264 and compiles succesfully. I have also compiled x264 and obtained libx264.a library. Both ffmpeg and libx264 are built from source. I can build ffmpeg without libx264 succesfully as well. Below you may find my script which tries to build ffmpeg with libx264.

  #!/bin/bash
  
  NDK=~/Android_NDK_r7b
  
  PLATFORM=$NDK/platforms/android-8/arch-arm/
  
  PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
  
  alitan=~/x264/ndk7_build
  
  function build_one
  
  {
  
  ./configure --target-os=linux \
  
  --prefix=$PREFIX \
  
  --enable-cross-compile \
  
  --extra-libs="-lgcc " \
  
  --arch=arm \
  
  --cc=$PREBUILT/bin/arm-linux-androideabi-gcc \
  
  --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
  
  --nm=$PREBUILT/bin/arm-linux-androideabi-nm \
  
  --sysroot=$PLATFORM \
  
  --extra-cflags=" -I$alitan/include" \
  
  --disable-shared \
  
  --enable-static \
  
  --extra-ldflags=" -L$alitan/lib " \
  
  --enable-version3 \
  
  --enable-gpl \
  
  --disable-doc \
  
  --disable-everything \
  
  --enable-libx264 \
  
  --enable-encoder=libx264 \
  
  $ADDITIONAL_CONFIGURE_FLAG
  
  
  
  make clean
  
  make -j4 install
  
  $PREBUILT/bin/arm-linux-androideabi-ar d libavcodec/libavcodec.a inverse.o
  
  $PREBUILT/bin/arm-linux-androideabi-ld -rpath-link=$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 libswscale/libswscale.a -lc -lm -lz -ldl -llog --warn-once --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-linux-androideabi/4.4.3/libgcc.a
  
  }
  
  
  
  #arm v7vfpv3
  
  CPU=armv7-a
  
  OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=vfpv3-d16 -marm -march=$CPU "
  
  PREFIX=./DONE/$CPU
  
  ADDITIONAL_CONFIGURE_FLAG=
  
  build_one

  Above script doesn't give me libx264.a in ffmpeg output builds.Several other scenarios are as follows.
  If I enable x264 encoder, I get undefined reference errors to some variables in x264.c (in libavcodec).
  If I enable shared in ffmpeg configure, I get an error which says it can't cd to my prefix directory (no permission issues by the way).

  I am using latest releases of ffmpeg and x264 (cloned the git today) and ndk 7. Ubuntu runs on VM, installed on Windows 7. For further details about my adventure of ffmpeg/x264 porting to Android, you may refer here.

  What should I do to use libx264 with ffmpeg ? I kept on trying this script with different configurations, removed all ffmpeg x264 folders and reinstalled them, but to no avail.

  Thanks a lot in advance.

  EDIT
  Below is my x264 build script. It builds fine, gives me the static library and the headers.

  export ARM_ROOT=/home/mehmet/Android_NDK_r7b
  
  export ARM_INC=$ARM_ROOT/platforms/android-8/arch-arm/usr/include/
  
  export ARM_LIB=$ARM_ROOT/platforms/android-8/arch-arm/usr/lib/
  
  export ARM_TOOL=$ARM_ROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
  
  export ARM_LIBO=$ARM_TOOL/lib/gcc/arm-linux-androideabi/4.4.3
  
  export PATH=$ARM_TOOL/bin:$PATH
  
  export PATH=$ARM_TOOL/arm-linux-androideabi/bin:$PATH
  
  export ARM_PRE=arm-linux-androideabi
  
  #tries to build for 4.4.3 toolchain
  
  
  
  ./configure --prefix=./ndk7_build \
  
  --disable-gpac \
  
  --extra-cflags=" -I$ARM_INC -fPIC -DANDROID -fpic -mthumb-interwork -ffunction-sections -funwind-tables -fstack-protector -fno-short-enums -D__ARM_ARCH_5__ -D__ARM_ARCH_5T__ -D__ARM_ARCH_5E__ -D__ARM_ARCH_5TE__ -Wno-psabi -march=armv5te -mtune=xscale -msoft-float -mthumb -Os -fomit-frame-pointer -fno-strict-aliasing -finline-limit=64 -DANDROID -Wa,--noexecstack -MMD -MP " \
  
  --extra-ldflags=" -nostdlib -Bdynamic -Wl,--no-undefined -Wl,-z,noexecstack -Wl,-z,nocopyreloc -Wl,-soname,/system/lib/libz.so -Wl,-rpath-link=$ARM_LIB,-dynamic-linker=/system/bin/linker -L$ARM_LIB -nostdlib $ARM_LIB/crtbegin_dynamic.o $ARM_LIB/crtend_android.o -lc -lm -ldl -lgcc " \
  
  --cross-prefix=${ARM_PRE}- \
  
  --disable-asm \
  
  --enable-static \
  
  --host=arm-linux \

  This is what happens on terminal when i enable libx264 encoder.

  STRIP   ffmpeg
  
  INSTALL install-progs-yes
  
  INSTALL ffmpeg
  
  INSTALL ffprobe
  
  libavcodec/libavcodec.a(libx264.o): In function `X264_frame':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:158: undefined reference to `x264_picture_init'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:178: undefined reference to `x264_encoder_reconfig'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:189: undefined reference to `x264_encoder_encode'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:195: undefined reference to `x264_encoder_delayed_frames'
  
  libavcodec/libavcodec.a(libx264.o): In function `encode_nals':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:100: undefined reference to `x264_bit_depth'
  
  libavcodec/libavcodec.a(libx264.o): In function `X264_close':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:230: undefined reference to `x264_encoder_close'
  
  libavcodec/libavcodec.a(libx264.o): In function `X264_init':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:283: undefined reference to `x264_param_default'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:291: undefined reference to `x264_param_default_preset'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:313: undefined reference to `x264_param_parse'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:448: undefined reference to `x264_param_apply_fastfirstpass'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:451: undefined reference to `x264_param_apply_profile'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:494: undefined reference to `x264_encoder_open_125'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:505: undefined reference to `x264_encoder_headers'

• libx264 encoder error in ffmpeg android build

  26 décembre 2013, par kerim yucel

  Right now, I have a ffmeg build script which recognizes libx264 and compiles succesfully. I have also compiled x264 and obtained libx264.a library. Both ffmpeg and libx264 are built from source. I can build ffmpeg without libx264 succesfully as well. Below you may find my script which tries to build ffmpeg with libx264.

  #!/bin/bash
  
  NDK=~/Android_NDK_r7b
  
  PLATFORM=$NDK/platforms/android-8/arch-arm/
  
  PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
  
  alitan=~/x264/ndk7_build
  
  function build_one
  
  {
  
  ./configure --target-os=linux \
  
  --prefix=$PREFIX \
  
  --enable-cross-compile \
  
  --extra-libs="-lgcc " \
  
  --arch=arm \
  
  --cc=$PREBUILT/bin/arm-linux-androideabi-gcc \
  
  --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
  
  --nm=$PREBUILT/bin/arm-linux-androideabi-nm \
  
  --sysroot=$PLATFORM \
  
  --extra-cflags=" -I$alitan/include" \
  
  --disable-shared \
  
  --enable-static \
  
  --extra-ldflags=" -L$alitan/lib " \
  
  --enable-version3 \
  
  --enable-gpl \
  
  --disable-doc \
  
  --disable-everything \
  
  --enable-libx264 \
  
  --enable-encoder=libx264 \
  
  $ADDITIONAL_CONFIGURE_FLAG
  
  
  
  make clean
  
  make -j4 install
  
  $PREBUILT/bin/arm-linux-androideabi-ar d libavcodec/libavcodec.a inverse.o
  
  $PREBUILT/bin/arm-linux-androideabi-ld -rpath-link=$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 libswscale/libswscale.a -lc -lm -lz -ldl -llog --warn-once --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-linux-androideabi/4.4.3/libgcc.a
  
  }
  
  
  
  #arm v7vfpv3
  
  CPU=armv7-a
  
  OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=vfpv3-d16 -marm -march=$CPU "
  
  PREFIX=./DONE/$CPU
  
  ADDITIONAL_CONFIGURE_FLAG=
  
  build_one

  Above script doesn’t give me libx264.a in ffmpeg output builds.Several other scenarios are as follows.
  If I enable x264 encoder, I get undefined reference errors to some variables in x264.c (in libavcodec).
  If I enable shared in ffmpeg configure, I get an error which says it can’t cd to my prefix directory (no permission issues by the way).

  I am using latest releases of ffmpeg and x264 (cloned the git today) and ndk 7. Ubuntu runs on VM, installed on Windows 7. For further details about my adventure of ffmpeg/x264 porting to Android, you may refer here.

  What should I do to use libx264 with ffmpeg ? I kept on trying this script with different configurations, removed all ffmpeg x264 folders and reinstalled them, but to no avail.

  Thanks a lot in advance.

  EDIT
  Below is my x264 build script. It builds fine, gives me the static library and the headers.

  export ARM_ROOT=/home/mehmet/Android_NDK_r7b
  
  export ARM_INC=$ARM_ROOT/platforms/android-8/arch-arm/usr/include/
  
  export ARM_LIB=$ARM_ROOT/platforms/android-8/arch-arm/usr/lib/
  
  export ARM_TOOL=$ARM_ROOT/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
  
  export ARM_LIBO=$ARM_TOOL/lib/gcc/arm-linux-androideabi/4.4.3
  
  export PATH=$ARM_TOOL/bin:$PATH
  
  export PATH=$ARM_TOOL/arm-linux-androideabi/bin:$PATH
  
  export ARM_PRE=arm-linux-androideabi
  
  #tries to build for 4.4.3 toolchain
  
  
  
  ./configure --prefix=./ndk7_build \
  
  --disable-gpac \
  
  --extra-cflags=" -I$ARM_INC -fPIC -DANDROID -fpic -mthumb-interwork -ffunction-sections -funwind-tables -fstack-protector -fno-short-enums -D__ARM_ARCH_5__ -D__ARM_ARCH_5T__ -D__ARM_ARCH_5E__ -D__ARM_ARCH_5TE__ -Wno-psabi -march=armv5te -mtune=xscale -msoft-float -mthumb -Os -fomit-frame-pointer -fno-strict-aliasing -finline-limit=64 -DANDROID -Wa,--noexecstack -MMD -MP " \
  
  --extra-ldflags=" -nostdlib -Bdynamic -Wl,--no-undefined -Wl,-z,noexecstack -Wl,-z,nocopyreloc -Wl,-soname,/system/lib/libz.so -Wl,-rpath-link=$ARM_LIB,-dynamic-linker=/system/bin/linker -L$ARM_LIB -nostdlib $ARM_LIB/crtbegin_dynamic.o $ARM_LIB/crtend_android.o -lc -lm -ldl -lgcc " \
  
  --cross-prefix=${ARM_PRE}- \
  
  --disable-asm \
  
  --enable-static \
  
  --host=arm-linux \

  This is what happens on terminal when i enable libx264 encoder.

  STRIP   ffmpeg
  
  INSTALL install-progs-yes
  
  INSTALL ffmpeg
  
  INSTALL ffprobe
  
  libavcodec/libavcodec.a(libx264.o): In function `X264_frame':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:158: undefined reference to `x264_picture_init'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:178: undefined reference to `x264_encoder_reconfig'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:189: undefined reference to `x264_encoder_encode'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:195: undefined reference to `x264_encoder_delayed_frames'
  
  libavcodec/libavcodec.a(libx264.o): In function `encode_nals':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:100: undefined reference to `x264_bit_depth'
  
  libavcodec/libavcodec.a(libx264.o): In function `X264_close':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:230: undefined reference to `x264_encoder_close'
  
  libavcodec/libavcodec.a(libx264.o): In function `X264_init':
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:283: undefined reference to `x264_param_default'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:291: undefined reference to `x264_param_default_preset'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:313: undefined reference to `x264_param_parse'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:448: undefined reference to `x264_param_apply_fastfirstpass'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:451: undefined reference to `x264_param_apply_profile'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:494: undefined reference to `x264_encoder_open_125'
  
  /home/mehmet/ffmpeg/libavcodec/libx264.c:505: undefined reference to `x264_encoder_headers'