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Dual 16x16 inter prediction.
Ronald S. Bultje authored
This patch introduces the concept of dual inter16x16 prediction. A
16x16 inter-predicted macroblock can use 2 references instead of 1,
where both references use the same mvmode (new, near/est, zero). In the
case of newmv, this means that two MVs are coded instead of one. The
frame can be encoded in 3 ways: all MBs single-prediction, all MBs dual
prediction, or per-MB single/dual prediction selection ("hybrid"), in
which case a single bit is coded per-MB to indicate whether the MB uses
single or dual inter prediction.

In the future, we can (maybe?) get further gains by mixing this with
Adrian's 32x32 work, per-segment dual prediction settings, or adding
support for dual splitmv/8x8mv inter prediction.

Gain (on derf-set, CQ mode) is ~2.8% (SSIM) or ~3.6% (glb PSNR). Most
gain is at medium/high bitrates, but there's minor gains at low bitrates
also. Output was confirmed to match between encoder and decoder.

Note for optimization people: this patch introduces a 2nd version of
16x16/8x8 sixtap/bilin functions, which does an avg instead of a
store. They may want to look and make sure this is implemented to
their satisfaction so we can optimize it best in the future.

Change-ID: I59dc84b07cbb3ccf073ac0f756d03d294cb19281
60cb39da
vpx Multi-Format Codec SDK
README - 19 May 2010

Welcome to the WebM VP8 Codec SDK!

COMPILING THE APPLICATIONS/LIBRARIES:
  The build system used is similar to autotools. Building generally consists of
  "configuring" with your desired build options, then using GNU make to build
  the application.

  1. Prerequisites

    * All x86 targets require the Yasm[1] assembler be installed.
    * All Windows builds require that Cygwin[2] be installed.
    * Building the documentation requires PHP[3] and Doxygen[4]. If you do not
      have these packages, you must pass --disable-install-docs to the
      configure script.

    [1]: http://www.tortall.net/projects/yasm
    [2]: http://www.cygwin.com
    [3]: http://php.net
    [4]: http://www.doxygen.org

  2. Out-of-tree builds
  Out of tree builds are a supported method of building the application. For
  an out of tree build, the source tree is kept separate from the object
  files produced during compilation. For instance:

    $ mkdir build
    $ cd build
    $ ../libvpx/configure <options>
    $ make

  3. Configuration options
  The 'configure' script supports a number of options. The --help option can be
  used to get a list of supported options:
    $ ../libvpx/configure --help

  4. Cross development
  For cross development, the most notable option is the --target option. The
  most up-to-date list of supported targets can be found at the bottom of the
  --help output of the configure script. As of this writing, the list of
  available targets is:

    armv5te-linux-rvct
    armv5te-linux-gcc
    armv5te-symbian-gcc
    armv6-darwin-gcc
    armv6-linux-rvct
    armv6-linux-gcc
    armv6-symbian-gcc
    iwmmxt-linux-rvct
    iwmmxt-linux-gcc
    iwmmxt2-linux-rvct
    iwmmxt2-linux-gcc
    armv7-linux-rvct
    armv7-linux-gcc
    mips32-linux-gcc
    ppc32-darwin8-gcc
    ppc32-darwin9-gcc
    ppc64-darwin8-gcc
    ppc64-darwin9-gcc
    ppc64-linux-gcc
    x86-darwin8-gcc
    x86-darwin8-icc
    x86-darwin9-gcc
    x86-darwin9-icc
    x86-linux-gcc
    x86-linux-icc
    x86-solaris-gcc
    x86-win32-vs7
    x86-win32-vs8
    x86_64-darwin9-gcc
    x86_64-linux-gcc
    x86_64-solaris-gcc
    x86_64-win64-vs8
    universal-darwin8-gcc
    universal-darwin9-gcc
    generic-gnu

  The generic-gnu target, in conjunction with the CROSS environment variable,
  can be used to cross compile architectures that aren't explicitly listed, if
  the toolchain is a cross GNU (gcc/binutils) toolchain. Other POSIX toolchains
  will likely work as well. For instance, to build using the mipsel-linux-uclibc
  toolchain, the following command could be used (note, POSIX SH syntax, adapt
  to your shell as necessary):

    $ CROSS=mipsel-linux-uclibc- ../libvpx/configure

  In addition, the executables to be invoked can be overridden by specifying the
  environment variables: CC, AR, LD, AS, STRIP, NM. Additional flags can be
  passed to these executables with CFLAGS, LDFLAGS, and ASFLAGS.

  5. Configuration errors
  If the configuration step fails, the first step is to look in the error log.
  This defaults to config.err. This should give a good indication of what went
  wrong. If not, contact us for support.

SUPPORT
  This library is an open source project supported by its community. Please
  please email webm-users@webmproject.org for help.